Isolation and characterization of the aconitate hydratase 4 (Aco4) gene from soybean

Aconitase catalyzes the reversible isomerization of two tricarboxylic acids, citrate and isocitrate, during the Krebs cycle. Five aconitase genes, namely, Aco1, Aco2, Aco3, Aco4, and Aco5, have been identified in soybean. Previously, Aco4 was mapped on chromosome 11. The purpose of this investigation was to isolate and sequence the candidate gene for Aco4. We mapped the Aco4 gene to a 148 kb region on chromosome 11 that contained 19 predicted genes. One of these, Glyma.11G080600, codes for aconitate hydratase. Sequencing of two isozyme variants (A-line and B-line) for Glyma.11G080600 revealed three synonymous and two non-synonymous substitutions. Perhaps, the two non-synonymous substitutions resulted in a variable isozyme pattern between the variants. Glyma.11G080600 contains a catalytic domain and a swivel domain that are known to catalyze isomerization of citrate to isocitrate and swiveling conformational change in the enzyme mechanism, respectively. Conservation of both the domains implies the role of Glyma.11G080600 in the interconversion of citrate and isocitrate. Glyma.11G080600 is expressed in most tissues, with maximum expression in leaves. Phylogenetic analysis of 25 genes from different species displayed three major clusters. Glyma.11G080600 (Aco4) and Glyma.01G162800, which are conserved in Glycine max (L.) Merr. and Glycine soja Siebold. & Zucc., may have common ancestry before G. max and G. soja split

Evaluation of spontaneous generation of allelic variation in soybean in response to sexual hybridization and stress

Intra-cultivar variation reported in pure lines of soybean has been hypothesized to result from genetic mechanisms contributing to de novo genetic variation. In this study we have detected allele switching by following segregation pattern of Aconitase-4 isozyme in sexual crosses and pure lines. In sexual crosses, one F2 plant showed switch at the Aconitase- 4 (Aco4) locus from the expected heterozygous genotype Aco4-ac to Aco4-ab. In the pure lines grown in a honeycomb planting design and treated with an accelerated aging test, multiple cases of allele switching were detected at the Aco4 locus. Both single and double switches were detected that were stable and heritable. These findings indicate that the generation of endogenous variation continues in pure lines as a result of intrinsic genetic mechanisms. With a long-term goal of understanding the genetic nature of the changes, we genetically mapped the Aco4 gene to a 3.3 cM region on Chromosome 11. The corresponding physical region is ~293 kb with 39 predicated genes. Of these, Glyma.11g080600 is of particular interest, as it shows 93% and 88% identity to Medicago truncatula and Arabidopsis aconitase genes, respectively. Further characterization of the soybean Aco4 gene may shed light on genetic mechanisms responsible for allele switching

Impressões foliares pleistocenas de Malvaceae na área de abrangência do Aproveitamento Hidroelétrico Jirau, Rondônia, Brasil

This paper aims to describe the morphology and taxonomic identification of ten angiosperm leaf impressions collected in Rio Madeira Formation outcrop in the area from Jirau Hydroeletric Dam, found by the team of Paleontological Research, Monitoring and Rescue Program. Due to the preservation and based on morphology, the specimens were identified at the genus level. All specimens belong to the family Malvaceae, and nine specimens were identified as Luehea and one specimen belongs to the genus Theobroma. Two samples were taken from the layer below to the fossiliferous bed, in order to carry dating by method “Accelerator Mass Spectrometry” (AMS C14). The dating pointed ages between 15.910 and 14.850 years calibrated BP. The genus reported here are common in current forest cover in the region of AHE Jirau, and their presences are also confirmed by palynological data obtained for the upper part of the Rio Madeira Formation.Este trabalho tem como objetivo descrever a morfologia foliar e realizar o reconhecimento taxonô- mico de dez impressões foliares de angiospermas coletadas em afloramento da Formação Rio Madeira na área de abrangência do Aproveitamento Hidrelétrico (AHE) Jirau, resgatadas pela equipe do Programa de Investiga- ção, Salvamento e Monitoramento Paleontológico. Devido à preservação e com base na descrição morfológica, os espécimes foram identificados até o nível de gênero. Todos os espécimes mostram caracteres que indicam sua relação com a família Malvaceae, nove deles com o gênero Luehea e um exemplar ao gênero Theobroma. Duas amostras foram retiradas da camada inferior àquela que concentra os fósseis, com o objetivo de realizar datação através do método “Accelerator Mass Spectrometry” (AMS C14). A datação apontou idades entre 15.910 e 14.850 anos calibrados AP. Os dois gêneros registrados são comuns na cobertura florestal atual na região do AHE Jirau, e a sua presença é também confirmada pelos dados palinológicos obtidos para a parte superior da Formação Rio Madeira