Caracterização, análise filogenética e perfil de expressão da família multigênica do fator de elongação 1 alfa (EF1α) de soja [Glycine max (L.) MERR.]: detecção de genes normalizadores para qPCR

Abstract

The elongation factor 1alpha (EF1α) is responsible for binding of aminoacyl-tRNA to the A site of the ribosome, acting thus the elongation phase of protein synthesis. The EF1α in plants is encoded by a multigene family with variable number of genes among species. The aim of this study was to characterize, analyze phylogenetic and elucidate the expression profile of EF1α genes in soybean during development, as well as select (s) gene (s) of the most stable reference for qRT-PCR assays in the development and conditions stress. In silico analyses in the genomes of soybean and other leguminous plants available in databases revealed gene families 3-6 members with conserved structure of 2 exons and 2 introns. Among the analyzed species (Glycine max, Cajanus cajan, Vigna unguiculata, Phaseolus vulgaris and Medicago truncatula) G. max was the one with the largest number of genes classified as EF1α 1a, 1b, 1c, 2a, 2b and 3 after phylogenetic analysis. The EF1α gene expression was studied in different tissues (flowers, pods, seeds, cotyledons, trifoliate and unifolioladas leaves, roots, hypocotyls and epicotyls) during the development of soybean. Expression analyses by qPCR revealed that the EF1α genes are functional and expressed in all tissues, however exhibit differential expression dependent on the tissue and developmental stage. Relative expression between genes members showed predominance of expression for 5 of the 6 genes analyzed: EF1α 1a: no predominance of expression; EF1α 1b: Germination and development hypocotyl; EF1α 1c: pods development; EF1α 2a: pods development, unifoliate and trifoliate leaves; EF1α 2b: pods development, unifoliate leaves; EF1α 3: Germination, flowers, roots, early stages development (hypocotyl and epicotyl). These data, together with the leaves and roots subjected to stress conditions (PEG and AS) were used to assess the stability of expression of different EF1α genes soybean through the programs GeNorm and NormFinder. For the analyses during development, four stable genes (UKN1, SKIP16, EF1β and MTP) were also used. EF1α genes were more stable in cotyledons (EF1α 3 and EF1α 1c); epicotyls (EF1α 1b, 2b and 1a), hypocotyls (EF1α 1a, EF1β and EF1α 1c); pods (EF1α 2a and EF1α 2b) and roots (EF1α 2b and UKN1) and less stable in trifoliate/unifoliolate leaves (UKN1 and SKIP16) and germinating seeds (EF1β and SKIP16). In leaves under stress conditions, through GeNorm analyses revealed that four genes (EF1α 2a> 1b> 2b> 1a) showed similar stability in the classification of stress for AS and PEG. Already in roots, distinct pattern of stability was found: EF1α 2a> 1c> 2b> 1b> 1a> 3 for PEG and EF1α 1c> 3> 2a> 1a> 2b> 1b to AS. These results were confirmed using the program NormFinder. In spite of changes in gene expression in different tissues in development and stress conditions were determined EF1α genes that can be used to normalize the qPCR assays in soybean and others leguminous plants (Phaseoleae tribe) seeing that EF1α genes orthologous were identified between these different species.