Tocopherol Accumulation and Temporal Expression Analysis of VTE1 and VTE5 Gene Family in Fruit of Two Contrasting Avocado Genotypes.

α-tocopherol is found in high concentrations in avocado fruit mesocarp, however, its accumulation and genetic control during maturation and ripening has not been elucidated. Based in the relevance of VTE1 and VTE5 genes in tocopherol biosynthesis and aiming to determine the association between tocopherol accumulation and expression of tocopherol biosynthetic genes, gene expression of VTE1 and VTE5 were evaluated through the time during three developmental stages: before harvest at 100, 160 and 220 days after flowering (DAF) and after harvest (220 DAF + 5) in two contrasting avocado genotypes (San Miguel and AVO40). San Miguel reached the highest levels at 220 DAF, whereas AVO40 increased α-tocopherol only after ripening (220 DAF + 5). A genome-wide search for VTE1 and VTE5 allowed to identify one and three genes, respectively. Both genotypes showed contrasting patterns of gene expression. Interestingly, AVO40 showed a highly positive correlation between α-tocopherol levels and gene expression of VTE1 and all VTE5 variants. On the other hand, San Miguel showed only a positive correlation between α-tocopherol level and VTE1gene expression.

Post-glacial expansion and population genetic divergence of mangrove species Avicennia germinans (L.) Stearn and Rhizophora mangle L. along the Mexican coast.

Mangrove forests in the Gulf of California, Mexico represent the northernmost populations along the Pacific coast and thus they are likely to be source populations for colonization at higher latitudes as climate becomes more favorable. Today, these populations are relatively small and fragmented and prior research has indicated that they are poor in genetic diversity. Here we set out to investigate whether the low diversity in this region was a result of recent colonization, or fragmentation and genetic drift of once more extensive mangroves due to climatic changes in the recent past. By sampling the two major mangrove species, Rhizophora mangle and Avicennia germinans, along the Pacific and Atlantic coasts of Mexico, we set out to test whether concordant genetic signals could elucidate recent evolution of the ecosystem. Genetic diversity of both mangrove species showed a decreasing trend toward northern latitudes along the Pacific coast. The lowest levels of genetic diversity were found at the range limits around the Gulf of California and the outer Baja California peninsula. Lack of a strong spatial genetic structure in this area and recent northern gene flow in A. germinans suggest recent colonization by this species. On the other hand, lack of a signal of recent northern dispersal in R. mangle, despite the higher dispersal capability of this species, indicates a longer presence of populations, at least in the southern Gulf of California. We suggest that the longer history, together with higher genetic diversity of R. mangle at the range limits, likely provides a gene pool better able to colonize northwards under climate change than A. germinans.