Stem borers (Lepidoptera) are common cereal pests. In many parts of the world, the species Ostrin... more Stem borers (Lepidoptera) are common cereal pests. In many parts of the world, the species Ostrinia nubilalis and Sesamia nonagrioides stand out as important insect pests of economically important crops such as maize. Their management relied mainly on transgenic host plant resistance over the last 25 years. Technologies based on the insecticidal properties of Bacillus thuringiensis-derived proteins allowed widespread pest population suppression, especially for O. nubilalis. However, the recent discovery of Bt resistance, which has revitalized interest in both pests' biology and management, may jeopardize the effectiveness of such transgenic technologies. Historical information on O. nubilalis bionomy may need to be reassessed in light of changing climate conditions and changing agricultural practices, as well as increased production of alternate host crops across its distribution range. The current paper examines the bioecology and historical research that has been conducted to manage these two important maize-boring pests.
We used three different approaches, a phylogenetic analysis, the principal component analysis, an... more We used three different approaches, a phylogenetic analysis, the principal component analysis, and Gabriel Graphs, to study the dispersion of the medfly from its geographic centre of origin. Our analysis was based on 13 enzyme polymorphisms detected electrophoretically in 15 natural populations coming from distinct geographic areas. The results indicate that (i) there is a clear‐cut separation of the native African from the introduced populations, (ii) the population from Spain seems to connect the African and the Mediterranean or American populations, and (iii) the Mediterranean populations as well as the American ones comprise two distinct groups of closely related populations.We have also estimated a phylogenetic tree for 3 species of the genus Ceratitis: C. capitata, C. rosa and C. nigra, based on electrophoretic data under the assumption of a molecular clock. The results suggest that C. capitata and C. rosa are more closely related to each other than either is to C. nigra.
In 2013, he received his Ph.D. diploma in Insect Biotechnology and Insect Molecular Biology from ... more In 2013, he received his Ph.D. diploma in Insect Biotechnology and Insect Molecular Biology from the AUA's Department of Biotechnology, specializing in Pest Control Science and Insect Biotechnology. His research mainly focuses on the use of RNA interference (RNAi) technology in designing insecticidal formulations of low environmental cost. Additionally, he is studying the molecular and physiological impact of various xenobiotics on the developmental processes of terrestrial arthropods. From 2015 to the present he has been collaborating with the AUA's Biotechnology Department as a part-time Assistant Professor. In 2018 he founded and currently runs a Pest Control Company headquartered in Argyroupolis, Attica, Greece, named "PROPEST FHG".
Insects enter in diapause in response to diverse environmental cues. During diapause, insects arr... more Insects enter in diapause in response to diverse environmental cues. During diapause, insects arrest their development and many genes are down-regulated while a small number of genes uniquely expressed at this time. This review aims to present available data regarding the regulation of diapause in the moth Sesamia nonagrioides (Lepidoptera: Noctuidae). Studying the transcriptional regulation of several genes (five heat shock proteins, two storage proteins and one juvenile hormone esterase) showed that these genes may play various roles in the diapause programming. The results show that SnoHsp19.5 gene was consistently expressed, while SnoHsp20.8 was down-regulated in deep diapause and was up-regulated at the termination of diapause. SnoHsc70 may play important roles in assisting protein conformation during specific stages of diapause. SnoHsp83 displays a similar pattern to SnoHsc70 under diapause conditions, when extra larval moults occur, indicating that could be involved in the developmental process that occurs between two moults. Expression of two SnoSP1 and SnoSP2 hexamerin genes was also observed throughout diapause. And the results lead us to the conclusion that larval diapause of S. nonagrioides is associated with continuous synthesis and accumulation of storage proteins. In addition, the transcript level of the carboxylesterase SnoJHER was higher in non-diapausing larvae than in diapausing ones. During the fifth instar of the non-diapausing and the ninth instar of the diapausing larvae, SnoJHER mRNAs reached higher expression levels on the days close to each larval molt.
Abstract Juvenile hormone esterase (JHE) is a carboxylesterase that plays critical roles in regul... more Abstract Juvenile hormone esterase (JHE) is a carboxylesterase that plays critical roles in regulating larval to adult transition by hydrolyzing the key developmental and reproductive hormone, juvenile hormone (JH). In the current work, we have cloned and sequenced a superfamily of juvenile hormone esterase related genes in Sesamia nonagrioides ( JHERs ). These seemed to have been recently multiplied from a common ancestral gene and consequently were inherited in the resulting populations as intron-less and intron-rich genes (loci). We sequenced three JHER genes (one intron-rich and two intron-less) and four cDNAs encoding for juvenile hormone esterase related sequences. Three cDNAs presented nucleotide deletions similar to alternative splicing events when compared with the introns of the intron-rich gene. The exons of the intron-rich gene were > 98% identical with one of the intron-less gene and the homologous sequences of all the four cDNAs. Moreover, the second intron-less gene seemed to be almost identical with one of the four cDNAs. The fourth cDNA contained an extensive (in-frame) deletion inside its ORF. This mRNA seems to be encoded by another gene which's deletion was generated by homologous recombination. Interestingly, our data revealed differential expression patterns for the four cDNAs. This study provides an initial assessment of the diversity of JHER genes in a population of Sesamia and presents this species as an attractive model to study the diversification of JHE-like esterase genes and their functional consequences.
The olive leaf trichomes are multicellular peltate hairs densely distributed mainly at the lower ... more The olive leaf trichomes are multicellular peltate hairs densely distributed mainly at the lower leaf epidermis. Although, non-glandular, they have gained much attention since they significantly contribute to abiotic and biotic stress tolerance of olive leaves. The exact mechanisms by which olive trichomes achieve these goals are not fully understood. They could act as mechanical barrier but they also accumulate high amounts of flavonoids among other secondary metabolites. However, little is currently known about the exact compounds they produce and the respective metabolic pathways. Here we present the first EST analysis from olive leaf trichomes by using 454-pyrosequencing. A total of 5368 unigenes were identified out of 7258 high quality reads with an average length of 262 bp. Blast search revealed that 27.5% of them had high homologies to known proteins. By using Blast2GO, 1079 unigenes (20.1%) were assigned at least one Gene Ontology (GO) term. Most of the genes were involved in cellular and metabolic processes and in binding functions followed by catalytic activity. A total of 521 transcripts were mapped to 67 KEGG pathways. Olive trichomes represent a tissue of highly unique transcriptome as per the genes involved in developmental processes and the secondary metabolism. The results indicate that mature olive trichomes are trancriptionally active, mainly through the potential production of enzymes that contribute to phenolic compounds with important roles in biotic and abiotic stress responses.
Restriction enzyme cleavage sites of mitochondrial DNA (mtDNA) from the Mediterranean fruit fly (... more Restriction enzyme cleavage sites of mitochondrial DNA (mtDNA) from the Mediterranean fruit fly (Ceratitis capitata) were found to vary among Mediterranean and New World populations. A restriction map for six populations (one from Greece and five from the New World) is constructed for the Mediterranean fruit fly. Six diagnostic restriction enzymes (EcoRI, EcoRV, HaeIII, HindIII, SstI, XbaI) are assigned three geographically distinct main types, CI, CII, and CIII.
Four natural Greek populations of Mediterranean fruit ßy, Ceratitis capitata (Wiedemann), was stu... more Four natural Greek populations of Mediterranean fruit ßy, Ceratitis capitata (Wiedemann), was studied for genetic variability at 25 enzyme loci. The comparison of polymorphism within and between populations shows two loci with high between-population heterozygosity (H T) and very high Þxation index (F ST) values, suggesting the presence of balancing selection. The gradual decline of common allele frequency of the polymorphic loci tested indicated that latitudinal clines are present in Greece. Indirect estimates of gene ßow based both on WrightÕs method (Nm) and on the SlatkinÕs method (Nm*), which depends on the frequencies of rare alleles found in only one population, revealed a substantial amount of gene ßow (Nm ϭ 3.493 and Nm* ϭ 3.197). These estimates of gene ßow may well explain why the "introduced" Greek populations of C. capitata, in spite of their low genetic variability, display the same polymorphic loci. Gene ßow in combination with natural selection and genetic drift may have played an important role to genetic differentiation in this species in Greece.
To evaluate germplasm variability and to discriminate between accessions of 'Ladolia', an... more To evaluate germplasm variability and to discriminate between accessions of 'Ladolia', an ancient olive variety of Cyprus, different accessions from a germplasm collection were screened with 11 selected oligonucleotide primers in RAPD-PCRs. A total of 49 polymorphic markers were scored, the combination of which resulted in 70 distinct electrophoretic patterns. Based on either unique or combined patterns, all accessions were identified. Seven genotype-specific markers were detected. One RAPD marker could distinguish accessions according to fruit size. Genetic similarities between accessions, estimated using the Dice similarity coefficient, indicated a high degree of genetic diversity among 'Ladolia' accessions. Genetic relationships were estimated by the unweighted pair-group method with arithmetic averaging (UPGMA) and principal components analysis (PCA). Three main groups of accessions were detected. The first group was generally composed of accessions with small-si...
Corn stalk borer Sesamia nonagrioides (Lefebvre) (Lepidoptera: Noctuidae) is among the most impor... more Corn stalk borer Sesamia nonagrioides (Lefebvre) (Lepidoptera: Noctuidae) is among the most important insect pests of corn in the Mediterranean basin. The mitochondrial DNA of this insect was purified and a restriction map was constructed. The size of the mtDNA genome is 16.3 kb. Genetic analysis of four corn stalk borer populations, collected from Greece (three populations) and Spain (one population), was undertaken using DNA sequences of the mtDNA cytochrome oxidase (CO) I and II genes. Sequencing of a 2079 bp region of these genes revealed 25 polymorphic sites among the populations. Five molecular RFLP markers, located in the mtDNA COI and COII genes, were surveyed, and two different haplotypes were detected. Phylogenetic analysis based on COI/COII nucleotide sequences revealed genetic differentiation between samples, and the results are discussed in relation to the geographic distribution of the corn stalk borer in two Mediterranean countries.
Allozyme variation at 25 gene loci was studied in fifteen populations of Ceratitis capitata (Wied... more Allozyme variation at 25 gene loci was studied in fifteen populations of Ceratitis capitata (Wiedemann) (medfly) originating from different countries. The study of genetic variation in natural populations of medfly was undertaken to identify different groups of polymorphic loci whose variation patterns might suggest different kinds of selection forces. The findings of this study are as follows: (1) the African populations have mean heterozygosity 17.8 % and the introduced 5.7 %. (2) An average population is polymorphic for 22.3 % of the gene loci and an average individual is heterozygous for 8.7 % of its gene loci. (3) The within population heterozygosity (H S) is divided into two groups. The first had an H S varying from 0 to 20 % and the second from 35 to 43 %. This abrupt transition between the two groups provides initial clues about selection on at least some loci. (4) The F ST (fixation index) values have a wide range among loci from 40.7 % (Pep 3) to 0 (Adh). The differentiation could be partly due to drift and partly by some sort of selection that affects particular genes. (5) Total heterozygosity (H T) could be separated into two groups with a gap between 20 % and 40 %. This distribution can sort out loci under purifying selection (low H T) and balancing selection (high H T). In conclusion, different evolutionary forces could have contributed to genetic changes during colonization by the medfly. In addition to the bottleneck effect, natural selection may have played an important role in the observed differences in the patterns of variation seen for different groups of loci in natural populations of C. capitata.
RNA interference (RNAi) is a transforming technology with high potential for practical applicatio... more RNA interference (RNAi) is a transforming technology with high potential for practical applications in biology, including specific and safe insect pest control. For developing RNAi-based pest-control products no general recommendations exist and the best strategy needs to be determined for each insect pest separately on a case-by-case basis. In this research, the potential of silencing the genes encoding the subunits of the ecdysone receptor complex, EcR and Ultraspiracle (USP) by RNAi was evaluated in the corn borer, Sesamia nonagrioides, using different delivery approaches and targeting different developmental stages. In conjunction with our previous research it is demonstrated that prepupae are sensitive to RNAi triggered by dsRNA injection and that feeding of dsRNA-expressing bacteria throughout S. nonagrioides’ larval life can lead to limited developmental malformations with no potent insecticidal results. Our results, consistent with previous studies, indicated a great fluctua...
Biological Control of Pest and Vector Insects, 2017
The development of insecticide formulations with new mechanisms of action (modes of action, MOAs)... more The development of insecticide formulations with new mechanisms of action (modes of action, MOAs) is a huge priority for pesticide industry. This priority has become apparent during the last few years after (a) the observed increase in insect resistance for the most widely used active substances and (b) the harmful effects of the excessive use of pesticides on human health, environment, beneficial insects and fish. Silencing of genes by RNAi (RNA interference) technology provides an alternative, selective to species level, environmentally friendly strategy to combat insect pests. Double-stranded RNA molecules (double-stranded RNAs, dsRNAs) targeting important developmental genes are taken up by the digestive tract of the targeted insect speciesand induce RNAi, which results in inhibition of growth, development and reproduction of the targeted insect species. After the rapid development of RNAi technology in the past 10 years, biotech industry is seeking for new applications aimed at producing environmentally friendly genetic insecticides or genetically modified plants (GMPs) that induce environmental RNAi in the targeted insect species. These technologies are expected on the market at the end of this decade. In this chapter, we exploit established methods involving recent initiatives of RNAi technology with respect to the development of new bio-insecticidal formulations.
Archives of Insect Biochemistry and Physiology, 2016
To obtain clues to the link between the molecular mechanism of circadian and photoperiod clocks, ... more To obtain clues to the link between the molecular mechanism of circadian and photoperiod clocks, we cloned two circadian clock genes, period (per) and timeless (tim) from the moth Sesamia nonagrioides, which undergoes facultative diapause controlled by photoperiod. Sequence analysis revealed a high degree of conservation among the compared insects fοr both genes. We also investigated the expression patterns of per and tim in brains of larvae growing under 16L:8D (long days), constant darkness (DD) and 10L:14D (short days) conditions by qPCR assays. The results showed that mRNA accumulations encoding both genes exhibited diel oscillations under different photoperiods. The oscillation of per and tim mRNA, under short-day photoperiod differed from long-day. The difference between longday and short-day conditions in the pattern of mRNA levels of per and tim appears to distinguish photoperiodic conditions clearly and both genes were influenced by photoperiod in different ways. We infer that not all photoperiodic clocks of insects interact with circadian clocks in the same fashion. Our results suggest that transcriptional regulations of the both clock genes act in the diapause programing in S. nonagrioides. The expression patterns of these genes are affected by photoperiod but runs with 24 h by entrainment to daily environmental cues.
Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology, 2017
To obtain clues to the link between the molecular mechanism of circadian and photoperiod clocks, ... more To obtain clues to the link between the molecular mechanism of circadian and photoperiod clocks, we have cloned the circadian clock gene cycle (Sncyc) in the corn stalk borer, Sesamia nonagrioides, which undergoes facultative diapause controlled by photoperiod. Sequence analysis revealed a high degree of conservation among insects for this gene. SnCYC consists of 667 amino acids and structural analysis showed that contains a BCTR domain in its C-terminal in addition to the common domains found in Drosophila CYC, i.e. bHLH, PAS-A, PAS-B domains. The results revealed that the sequence of Sncyc showed a similarity to that of its mammalian orthologue, Bmal1. We also investigated the expression patterns of Sncyc in brain of larvae growing under longday 16L: 8D (LD), constant darkness (DD) and short-day 10L: 14D (SD) conditions using qRT-PCR assays. The mRNAs of Sncyc expression was rhythmic in LD, DD and SD cycles. Also, is remarkable that the photoperiodic conditions affect the expression patterns and/or amplitudes of circadian clock gene Sncyc. This gene is associated with diapause in S. nonagrioides, because under SD (diapause conditions) the photoperiodic signal altered mRNA accumulation. Sequence and expression analysis of cyc in S. nonagrioides show interesting differences compared to Drosophila where this gene does not oscillate or change in expression patterns in response to photoperiod, suggesting that this species is an interesting new model to study the molecular control of insect circadian and photoperiodic clocks.
The Mediterranean corn borer Sesamia nonagrioides (Lepidoptera: Noctuidae) has a unique and recen... more The Mediterranean corn borer Sesamia nonagrioides (Lepidoptera: Noctuidae) has a unique and recently multiplied juvenile hormone esterase gene family (SnJHER) with particular transcriptional profi les and functional characteristics. Unlike conventional juvenile hormone esterase genes (JHEs), the SnJHER gene family seems to have been recently evolved from a common ancestral JHER gene. SnJHERs seem to be regulated by both ecdysone agonists and xenobiotics, while their real role in development remains to be exploited. In this study we transiently expressed the major SnJHER isoform in Bm5 and Hi5 cell lines. The JHER-expressing cell lines showed increased toxicity when treated with the juvenile hormone analog methoprene. Moreover baculovirus-mediated transient gene transduction of the SnJHER gene in larvae of S. nonagrioides resulted in moulting abnormalities. These were more marked after the additional application of the juvenile hormone analog methoprene. Our results indicate a potential mechanism by which SnJHER interferes with normal JHE.
Stem borers (Lepidoptera) are common cereal pests. In many parts of the world, the species Ostrin... more Stem borers (Lepidoptera) are common cereal pests. In many parts of the world, the species Ostrinia nubilalis and Sesamia nonagrioides stand out as important insect pests of economically important crops such as maize. Their management relied mainly on transgenic host plant resistance over the last 25 years. Technologies based on the insecticidal properties of Bacillus thuringiensis-derived proteins allowed widespread pest population suppression, especially for O. nubilalis. However, the recent discovery of Bt resistance, which has revitalized interest in both pests' biology and management, may jeopardize the effectiveness of such transgenic technologies. Historical information on O. nubilalis bionomy may need to be reassessed in light of changing climate conditions and changing agricultural practices, as well as increased production of alternate host crops across its distribution range. The current paper examines the bioecology and historical research that has been conducted to manage these two important maize-boring pests.
We used three different approaches, a phylogenetic analysis, the principal component analysis, an... more We used three different approaches, a phylogenetic analysis, the principal component analysis, and Gabriel Graphs, to study the dispersion of the medfly from its geographic centre of origin. Our analysis was based on 13 enzyme polymorphisms detected electrophoretically in 15 natural populations coming from distinct geographic areas. The results indicate that (i) there is a clear‐cut separation of the native African from the introduced populations, (ii) the population from Spain seems to connect the African and the Mediterranean or American populations, and (iii) the Mediterranean populations as well as the American ones comprise two distinct groups of closely related populations.We have also estimated a phylogenetic tree for 3 species of the genus Ceratitis: C. capitata, C. rosa and C. nigra, based on electrophoretic data under the assumption of a molecular clock. The results suggest that C. capitata and C. rosa are more closely related to each other than either is to C. nigra.
In 2013, he received his Ph.D. diploma in Insect Biotechnology and Insect Molecular Biology from ... more In 2013, he received his Ph.D. diploma in Insect Biotechnology and Insect Molecular Biology from the AUA's Department of Biotechnology, specializing in Pest Control Science and Insect Biotechnology. His research mainly focuses on the use of RNA interference (RNAi) technology in designing insecticidal formulations of low environmental cost. Additionally, he is studying the molecular and physiological impact of various xenobiotics on the developmental processes of terrestrial arthropods. From 2015 to the present he has been collaborating with the AUA's Biotechnology Department as a part-time Assistant Professor. In 2018 he founded and currently runs a Pest Control Company headquartered in Argyroupolis, Attica, Greece, named "PROPEST FHG".
Insects enter in diapause in response to diverse environmental cues. During diapause, insects arr... more Insects enter in diapause in response to diverse environmental cues. During diapause, insects arrest their development and many genes are down-regulated while a small number of genes uniquely expressed at this time. This review aims to present available data regarding the regulation of diapause in the moth Sesamia nonagrioides (Lepidoptera: Noctuidae). Studying the transcriptional regulation of several genes (five heat shock proteins, two storage proteins and one juvenile hormone esterase) showed that these genes may play various roles in the diapause programming. The results show that SnoHsp19.5 gene was consistently expressed, while SnoHsp20.8 was down-regulated in deep diapause and was up-regulated at the termination of diapause. SnoHsc70 may play important roles in assisting protein conformation during specific stages of diapause. SnoHsp83 displays a similar pattern to SnoHsc70 under diapause conditions, when extra larval moults occur, indicating that could be involved in the developmental process that occurs between two moults. Expression of two SnoSP1 and SnoSP2 hexamerin genes was also observed throughout diapause. And the results lead us to the conclusion that larval diapause of S. nonagrioides is associated with continuous synthesis and accumulation of storage proteins. In addition, the transcript level of the carboxylesterase SnoJHER was higher in non-diapausing larvae than in diapausing ones. During the fifth instar of the non-diapausing and the ninth instar of the diapausing larvae, SnoJHER mRNAs reached higher expression levels on the days close to each larval molt.
Abstract Juvenile hormone esterase (JHE) is a carboxylesterase that plays critical roles in regul... more Abstract Juvenile hormone esterase (JHE) is a carboxylesterase that plays critical roles in regulating larval to adult transition by hydrolyzing the key developmental and reproductive hormone, juvenile hormone (JH). In the current work, we have cloned and sequenced a superfamily of juvenile hormone esterase related genes in Sesamia nonagrioides ( JHERs ). These seemed to have been recently multiplied from a common ancestral gene and consequently were inherited in the resulting populations as intron-less and intron-rich genes (loci). We sequenced three JHER genes (one intron-rich and two intron-less) and four cDNAs encoding for juvenile hormone esterase related sequences. Three cDNAs presented nucleotide deletions similar to alternative splicing events when compared with the introns of the intron-rich gene. The exons of the intron-rich gene were > 98% identical with one of the intron-less gene and the homologous sequences of all the four cDNAs. Moreover, the second intron-less gene seemed to be almost identical with one of the four cDNAs. The fourth cDNA contained an extensive (in-frame) deletion inside its ORF. This mRNA seems to be encoded by another gene which's deletion was generated by homologous recombination. Interestingly, our data revealed differential expression patterns for the four cDNAs. This study provides an initial assessment of the diversity of JHER genes in a population of Sesamia and presents this species as an attractive model to study the diversification of JHE-like esterase genes and their functional consequences.
The olive leaf trichomes are multicellular peltate hairs densely distributed mainly at the lower ... more The olive leaf trichomes are multicellular peltate hairs densely distributed mainly at the lower leaf epidermis. Although, non-glandular, they have gained much attention since they significantly contribute to abiotic and biotic stress tolerance of olive leaves. The exact mechanisms by which olive trichomes achieve these goals are not fully understood. They could act as mechanical barrier but they also accumulate high amounts of flavonoids among other secondary metabolites. However, little is currently known about the exact compounds they produce and the respective metabolic pathways. Here we present the first EST analysis from olive leaf trichomes by using 454-pyrosequencing. A total of 5368 unigenes were identified out of 7258 high quality reads with an average length of 262 bp. Blast search revealed that 27.5% of them had high homologies to known proteins. By using Blast2GO, 1079 unigenes (20.1%) were assigned at least one Gene Ontology (GO) term. Most of the genes were involved in cellular and metabolic processes and in binding functions followed by catalytic activity. A total of 521 transcripts were mapped to 67 KEGG pathways. Olive trichomes represent a tissue of highly unique transcriptome as per the genes involved in developmental processes and the secondary metabolism. The results indicate that mature olive trichomes are trancriptionally active, mainly through the potential production of enzymes that contribute to phenolic compounds with important roles in biotic and abiotic stress responses.
Restriction enzyme cleavage sites of mitochondrial DNA (mtDNA) from the Mediterranean fruit fly (... more Restriction enzyme cleavage sites of mitochondrial DNA (mtDNA) from the Mediterranean fruit fly (Ceratitis capitata) were found to vary among Mediterranean and New World populations. A restriction map for six populations (one from Greece and five from the New World) is constructed for the Mediterranean fruit fly. Six diagnostic restriction enzymes (EcoRI, EcoRV, HaeIII, HindIII, SstI, XbaI) are assigned three geographically distinct main types, CI, CII, and CIII.
Four natural Greek populations of Mediterranean fruit ßy, Ceratitis capitata (Wiedemann), was stu... more Four natural Greek populations of Mediterranean fruit ßy, Ceratitis capitata (Wiedemann), was studied for genetic variability at 25 enzyme loci. The comparison of polymorphism within and between populations shows two loci with high between-population heterozygosity (H T) and very high Þxation index (F ST) values, suggesting the presence of balancing selection. The gradual decline of common allele frequency of the polymorphic loci tested indicated that latitudinal clines are present in Greece. Indirect estimates of gene ßow based both on WrightÕs method (Nm) and on the SlatkinÕs method (Nm*), which depends on the frequencies of rare alleles found in only one population, revealed a substantial amount of gene ßow (Nm ϭ 3.493 and Nm* ϭ 3.197). These estimates of gene ßow may well explain why the "introduced" Greek populations of C. capitata, in spite of their low genetic variability, display the same polymorphic loci. Gene ßow in combination with natural selection and genetic drift may have played an important role to genetic differentiation in this species in Greece.
To evaluate germplasm variability and to discriminate between accessions of 'Ladolia', an... more To evaluate germplasm variability and to discriminate between accessions of 'Ladolia', an ancient olive variety of Cyprus, different accessions from a germplasm collection were screened with 11 selected oligonucleotide primers in RAPD-PCRs. A total of 49 polymorphic markers were scored, the combination of which resulted in 70 distinct electrophoretic patterns. Based on either unique or combined patterns, all accessions were identified. Seven genotype-specific markers were detected. One RAPD marker could distinguish accessions according to fruit size. Genetic similarities between accessions, estimated using the Dice similarity coefficient, indicated a high degree of genetic diversity among 'Ladolia' accessions. Genetic relationships were estimated by the unweighted pair-group method with arithmetic averaging (UPGMA) and principal components analysis (PCA). Three main groups of accessions were detected. The first group was generally composed of accessions with small-si...
Corn stalk borer Sesamia nonagrioides (Lefebvre) (Lepidoptera: Noctuidae) is among the most impor... more Corn stalk borer Sesamia nonagrioides (Lefebvre) (Lepidoptera: Noctuidae) is among the most important insect pests of corn in the Mediterranean basin. The mitochondrial DNA of this insect was purified and a restriction map was constructed. The size of the mtDNA genome is 16.3 kb. Genetic analysis of four corn stalk borer populations, collected from Greece (three populations) and Spain (one population), was undertaken using DNA sequences of the mtDNA cytochrome oxidase (CO) I and II genes. Sequencing of a 2079 bp region of these genes revealed 25 polymorphic sites among the populations. Five molecular RFLP markers, located in the mtDNA COI and COII genes, were surveyed, and two different haplotypes were detected. Phylogenetic analysis based on COI/COII nucleotide sequences revealed genetic differentiation between samples, and the results are discussed in relation to the geographic distribution of the corn stalk borer in two Mediterranean countries.
Allozyme variation at 25 gene loci was studied in fifteen populations of Ceratitis capitata (Wied... more Allozyme variation at 25 gene loci was studied in fifteen populations of Ceratitis capitata (Wiedemann) (medfly) originating from different countries. The study of genetic variation in natural populations of medfly was undertaken to identify different groups of polymorphic loci whose variation patterns might suggest different kinds of selection forces. The findings of this study are as follows: (1) the African populations have mean heterozygosity 17.8 % and the introduced 5.7 %. (2) An average population is polymorphic for 22.3 % of the gene loci and an average individual is heterozygous for 8.7 % of its gene loci. (3) The within population heterozygosity (H S) is divided into two groups. The first had an H S varying from 0 to 20 % and the second from 35 to 43 %. This abrupt transition between the two groups provides initial clues about selection on at least some loci. (4) The F ST (fixation index) values have a wide range among loci from 40.7 % (Pep 3) to 0 (Adh). The differentiation could be partly due to drift and partly by some sort of selection that affects particular genes. (5) Total heterozygosity (H T) could be separated into two groups with a gap between 20 % and 40 %. This distribution can sort out loci under purifying selection (low H T) and balancing selection (high H T). In conclusion, different evolutionary forces could have contributed to genetic changes during colonization by the medfly. In addition to the bottleneck effect, natural selection may have played an important role in the observed differences in the patterns of variation seen for different groups of loci in natural populations of C. capitata.
RNA interference (RNAi) is a transforming technology with high potential for practical applicatio... more RNA interference (RNAi) is a transforming technology with high potential for practical applications in biology, including specific and safe insect pest control. For developing RNAi-based pest-control products no general recommendations exist and the best strategy needs to be determined for each insect pest separately on a case-by-case basis. In this research, the potential of silencing the genes encoding the subunits of the ecdysone receptor complex, EcR and Ultraspiracle (USP) by RNAi was evaluated in the corn borer, Sesamia nonagrioides, using different delivery approaches and targeting different developmental stages. In conjunction with our previous research it is demonstrated that prepupae are sensitive to RNAi triggered by dsRNA injection and that feeding of dsRNA-expressing bacteria throughout S. nonagrioides’ larval life can lead to limited developmental malformations with no potent insecticidal results. Our results, consistent with previous studies, indicated a great fluctua...
Biological Control of Pest and Vector Insects, 2017
The development of insecticide formulations with new mechanisms of action (modes of action, MOAs)... more The development of insecticide formulations with new mechanisms of action (modes of action, MOAs) is a huge priority for pesticide industry. This priority has become apparent during the last few years after (a) the observed increase in insect resistance for the most widely used active substances and (b) the harmful effects of the excessive use of pesticides on human health, environment, beneficial insects and fish. Silencing of genes by RNAi (RNA interference) technology provides an alternative, selective to species level, environmentally friendly strategy to combat insect pests. Double-stranded RNA molecules (double-stranded RNAs, dsRNAs) targeting important developmental genes are taken up by the digestive tract of the targeted insect speciesand induce RNAi, which results in inhibition of growth, development and reproduction of the targeted insect species. After the rapid development of RNAi technology in the past 10 years, biotech industry is seeking for new applications aimed at producing environmentally friendly genetic insecticides or genetically modified plants (GMPs) that induce environmental RNAi in the targeted insect species. These technologies are expected on the market at the end of this decade. In this chapter, we exploit established methods involving recent initiatives of RNAi technology with respect to the development of new bio-insecticidal formulations.
Archives of Insect Biochemistry and Physiology, 2016
To obtain clues to the link between the molecular mechanism of circadian and photoperiod clocks, ... more To obtain clues to the link between the molecular mechanism of circadian and photoperiod clocks, we cloned two circadian clock genes, period (per) and timeless (tim) from the moth Sesamia nonagrioides, which undergoes facultative diapause controlled by photoperiod. Sequence analysis revealed a high degree of conservation among the compared insects fοr both genes. We also investigated the expression patterns of per and tim in brains of larvae growing under 16L:8D (long days), constant darkness (DD) and 10L:14D (short days) conditions by qPCR assays. The results showed that mRNA accumulations encoding both genes exhibited diel oscillations under different photoperiods. The oscillation of per and tim mRNA, under short-day photoperiod differed from long-day. The difference between longday and short-day conditions in the pattern of mRNA levels of per and tim appears to distinguish photoperiodic conditions clearly and both genes were influenced by photoperiod in different ways. We infer that not all photoperiodic clocks of insects interact with circadian clocks in the same fashion. Our results suggest that transcriptional regulations of the both clock genes act in the diapause programing in S. nonagrioides. The expression patterns of these genes are affected by photoperiod but runs with 24 h by entrainment to daily environmental cues.
Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology, 2017
To obtain clues to the link between the molecular mechanism of circadian and photoperiod clocks, ... more To obtain clues to the link between the molecular mechanism of circadian and photoperiod clocks, we have cloned the circadian clock gene cycle (Sncyc) in the corn stalk borer, Sesamia nonagrioides, which undergoes facultative diapause controlled by photoperiod. Sequence analysis revealed a high degree of conservation among insects for this gene. SnCYC consists of 667 amino acids and structural analysis showed that contains a BCTR domain in its C-terminal in addition to the common domains found in Drosophila CYC, i.e. bHLH, PAS-A, PAS-B domains. The results revealed that the sequence of Sncyc showed a similarity to that of its mammalian orthologue, Bmal1. We also investigated the expression patterns of Sncyc in brain of larvae growing under longday 16L: 8D (LD), constant darkness (DD) and short-day 10L: 14D (SD) conditions using qRT-PCR assays. The mRNAs of Sncyc expression was rhythmic in LD, DD and SD cycles. Also, is remarkable that the photoperiodic conditions affect the expression patterns and/or amplitudes of circadian clock gene Sncyc. This gene is associated with diapause in S. nonagrioides, because under SD (diapause conditions) the photoperiodic signal altered mRNA accumulation. Sequence and expression analysis of cyc in S. nonagrioides show interesting differences compared to Drosophila where this gene does not oscillate or change in expression patterns in response to photoperiod, suggesting that this species is an interesting new model to study the molecular control of insect circadian and photoperiodic clocks.
The Mediterranean corn borer Sesamia nonagrioides (Lepidoptera: Noctuidae) has a unique and recen... more The Mediterranean corn borer Sesamia nonagrioides (Lepidoptera: Noctuidae) has a unique and recently multiplied juvenile hormone esterase gene family (SnJHER) with particular transcriptional profi les and functional characteristics. Unlike conventional juvenile hormone esterase genes (JHEs), the SnJHER gene family seems to have been recently evolved from a common ancestral JHER gene. SnJHERs seem to be regulated by both ecdysone agonists and xenobiotics, while their real role in development remains to be exploited. In this study we transiently expressed the major SnJHER isoform in Bm5 and Hi5 cell lines. The JHER-expressing cell lines showed increased toxicity when treated with the juvenile hormone analog methoprene. Moreover baculovirus-mediated transient gene transduction of the SnJHER gene in larvae of S. nonagrioides resulted in moulting abnormalities. These were more marked after the additional application of the juvenile hormone analog methoprene. Our results indicate a potential mechanism by which SnJHER interferes with normal JHE.
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Papers by Anna Kourti