Escuela de Biociencias

The endangered species Strombus gigas is a marine gastropod of significant economic importance through the Greater Caribbean region. In contrast to phenotypic plasticity, the role of genetics on shell variations in S. gigas has not been addressed so far, despite its importance in evolution, management and conservation of this species. This work used geometric morphometrics to investigate the phenotypic variation of 219 shells of S. gigas from eight sites of the Colombian Southwest Caribbean. Differences in mean size between sexes and among sites were contrasted by analysis of variance. Allometry was tested by multivariate regression and the hypothesis of common slope was contrasted by covariance multivariate analysis. Differences in the shell shape among sites were analyzed by principal component analysis. Sexual size dimorphism was not significant, whereas sexual shape dimorphism was significant and variable across sites. Differences in the shell shape among sites were concordant with genetic differences based on microsatellite data, supporting its genetic background. Besides, differences in the shell shape between populations genetically similar suggest a role of phenotypic plasticity in the morphometric variation of the shell shape. These outcomes evidence the role of genetic background and phenotypic plasticity in the shell shape of S. gigas. Thus, geometric morphometrics of shell shape may constitute a complementary tool to explore the genetic diversity of this species. Rev. Biol. Trop. 64 (4): 000-000. Epub 2016 December 01.

Para lograr la identificación y demostración de algunas propiedades fisicoquímicas en alcoholes primarios, secundarios y terciarios, se procedió a efectuar tres ensayos donde a partir de la solubilidad en agua y en éter, en lo que respecta a las propiedades físicas; y de las reacciones con un metal álcali o de la oxidación a partir de dicromato de Sodio; en lo que atañe a las reacciones químicas, se logró una comprobación y verificación de cada uno de los procesos que se llevan a cabo dentro de una función oxigenada cómo lo es el grupo alcohol, así como también se demostraron algunas excepciones dentro de este grupo y el comportamiento de sus moléculas en medios polares y apolares.

La producción de etanol por fermentación es influenciada por la presencia de iones metálicos como hierro y zinc dado que son cofactores de la enzima alcohol deshidrogenasa. El estudio de este efecto permitiría identificar el comportamiento de los microorganismos fermentadores en sustratos industriales que contienen altas concentraciones de este tipo de iones. Este trabajo evaluó la producción de biomasa, los azúcares residuales y la producción de etanol por fermentación de tres cepas de S. cerevisiae, CBS8066, recombinantes GG570-CIBI y GG570-CIBII, bajo el efecto de la adición de hierro a 0, 50 y 150 mM, y zinc a 0 y 50 mM. Las cepas presentaron inhibición en la producción de biomasa y etanol bajo efecto de iones de hierro y zinc, siendo dicha inhibición mayor al estar en presencia de zinc o alta concentración de hierro. GG570-CIBI mostró disminución en producción de biomasa de 4 g/L y una caída en producción de etanol de 40% en el tratamiento 150 mM hierro-50 mM zinc (con respecto al tratamiento basal). GG570-CIBII fue la menos afectada con inhibición en la producción de etanol inferior a 11% a las 20 h de fermentación. Adicionalmente, presentó la mayor producción de etanol cuando hubo adición de 150 mM Fe con o sin adición de zinc, siendo dicha producción entre un 9 y 14% superior a la de las cepas CBS8066 y GG570-CIBI respectivamente, bajo las mismas condiciones. Posteriormente, GG570-CIBII será evaluada en sustratos industriales debido a su menor inhibición en la producción de etanol, permitiendo así obtener mejores rendimientos.

Rubber (Hevea brasiliensis) represents a potential species for reforestation and commercial exploitation programmes in tropical countries such as Colombia. The genetic variability of a rubber collection kept at the Paraguaicito Experimental Station in Buenavista in the Quindio department of Colombia was studied to improve knowledge regarding this species and make better use of the trees available. A total of 25 clones, six from South-America, 17 from Asia and two from Central-America were selected and analysed using RAPDs. DNA samples isolated from the trees were screened with 102 primers, 23 of which revealed polymorphism. Although a high degree of similarity was found, clustering analysis of the data led to differentiating the rubber trees in terms of their geographical origin. Furthermore, genetic relationships were found amongst the clones which could help in selecting parents for use in breeding programmes and designing strategies for conserving clones having desirable agronomic traits.

Examination of the hemagglutinating activity of extracts from seeds of Erythrina coraflodendron at various maturation stages revealed that the level of lectin increases markedly past mid-maturation. Seeds at this stage of maturation served as a source of mRNA for the construction of an expression cDNA library in the vector 3. Zap, which generates fusion proteins with an N-terminal portion of B-galactosidase. The library was screened with rabbit polyclonal anti-ECorL antiserum. Four immunopositive clones were isolated. Western blot analysis of cell extracts from one of the clones (pIEcL-B) showed a 36 kDa protein that reacted with the antiserum, as well as with a mouse monoclonal antibody raised against the lectin. DNA sequence analysis by the chain termination method revealed that clone p&l-C has an insert of 1017 bp with the entire coding sequence of ECorL, beginning with an initiation codon ATG at position 26 and ending with stop codon TAA at position 868. This fragment encodes a polypeptide of 281 amino acids consisting of a signal leader sequence of 25 amino acids and a mature protein of 256 amino acids. The deduced amino acid sequence from this fragment is identical to the sequence of the first 244 amino acids of ECorL, as determined at the protein level, except at 7 positions.

Examination of the three-dimensional structure of Erythrina corallodendron lectin (ECorL) in complex with a ligand (lactose), the first of its kind for a Gal/GalNAc-specific lectin [(1991) Science 254, 862-8661, revealed the presence of a hydrophobic cavity, surrounded by Tyr""' and Prol"-Trp"', which can accommodate bulky substituents such as acetamido or dansylamido (NDns) at C-2 of the lectin-bound galactose. Comparison of the primary sequence of ECorL with that of soybean agglutinin, specific for galactose and its C-2 substituted derivatives, and ofpeanut agglutinin, specific for galactose only, showed that in soybean agglutinin, Tyr"' is retained, and Pro'34-Trp'35 is replaced by Ser-Trp, whereas in peanut agglutinin, the former residue is replaced by Thr and the dipeptide by Ser-Glu-Tyr-Asn. Three mutants of ECorL were therefore constructed: L2, in which Pro'34-Trp'35 was replaced by Ser-Glu-Tyr-Asn; YlO8T, in which Tyr" was replaced by Thr and the double mutant L2; Y108T. They were expressed in Escherichiu co/i, as done for recombinant ECorL [(1992) Eur. J. Biochem. 205, 575-5811. The mutants had the same hemagglutinating activity as native or rECorL. Their specificity for galactose, GalNAc and MepGalNDns was examined by inhibition of hemagglutination and of the binding of the lectin to immobilized asialofetuin; in addition, their association constants with MeaGalNDns and Me/JGalNDns were measured by spectrofluorimetric titration. The results showed that Yl08T had essentially similar specificity as the native and recombinant lectins. The affinity of L2 and L2;Yl08T for galactose was also the same as ECorL, but they had a lower affinity for GalNAc and markedly diminished affinity for the dansyl sugars (up to 43 times, or 2 kcal, less). This appears to be largely due to steric hindrance by the two additional amino acids present in the cavity region in these mutants. Our findings also provide an explanation for the inability of PNA to accommodate C-2-substituted galactose derivatives at its primary subsite.

The Guatemalan potato moth, Tecia solanivora (Lepidoptera: Gelechiidae), is one of the most important pests affecting potatoes in northern South America, causing crop losses ranging from 50 to 100%. In this work, we isolated a native strain of Bacillus ...

The levels of native fungitoxic perinaphthenone phytoalexins in susceptible Musa varieties (banana), which are commercially grown in large plantations, are too low to provide plants with long-lasting protection against highly pathogenic fungi. Novel strategies for plant protection are necessary to reduce crop losses and to prevent the development of resistant fungal strains. The synthesis of novel fungicides based on the structures of perinaphthenone natural products is considered to be a promising strategy. Thirteen substituted perinaphthenones, among them two known natural products (1, 2) and 11 synthetics (3-13), were evaluated for their activity against Mycosphaerella fijiensis, and their half-maximal inhibitory concentrations (IC 50 ) were calculated to establish structure-activity relationships (SAR). A SAR trend was hypothesized, leading to the design of a new compound, 4-methoxy-2-nitro-1H-phenalen-1-one ; the new compound displayed significantly enhanced in vitro activity against M. fijiensis compared to other perinaphthenone derivatives. The activity of 14 was comparable to that of two commercial fungicides.

Two perinaphthenone-type compounds (1 and 2) were isolated together with four known phenylphenalenones (3-6) from the rhizomes of Musa acuminata var. "Yangambi km 5". The structures of the new phenalenones were assigned as 2-hydroxy-1H-phenalen-1-one (1) and 2-methoxy-1H-phenalen-1-one (2) on the basis of their spectroscopic data and were confirmed by synthesis. Compounds 1 and 2 displayed significantly enhanced activity against Mycosphaerella fijiensis in comparison with other phenylphenalenones.

The cDNA of the Erythrina corallodendron lectin (ECorL) has been expressed in Escherichia coli. For this purpose, an NcoI site was inserted into the cDNA coding for the lectin precursor [Arango, R., Rozenblatt, S. & Sharon, N. (1990) FEBS Lett. 264, 109-1121 immediately before the codon GTG (103 -105) which codes for the N-terminal valine of the mature lectin. This introduced an ATG codon for a methionine preceding the valine. The mutated cDNA was ligated into pUC-8, then subcloned into the expression vector pET-3d, which carries a strong promoter derived from gene 10 of the phage T7. The recombinant plasmid was introduced into the E. coli lysogenic strain BL21(DE3).

Male sterility is a very important characteristic for environmental safety in genetically modified (GM ) plants, particularly in the release of transgenic plants in the centers of origin or high biodiversity areas. In order to contribute to the development of environmentally safe agricultural technologies that allow the proper use of transgenic potato crops in Colombia, this project developed transgenic potato cry1Ac of Bacillus thuringiensis (Bt), lines that are potentially resistant to T. solanivora, from the male-sterile variety Pastusa Suprema (PS) (Solanum tuberosum ssp. andigena). Modifications were made to the Agrobacterium tumefaciens mediated-transformation protocol which allowed the genetic transformation of leaves of in vitro plants, with transformation efficiencies of 22 and 37%. Cry1Ac protein levels in transgenic leaves ranged from 88 to 639 ng mg-1 of fresh leaf tissue, suggesting a better potential plant resistance. This is the first report on transgenic lines with p...