Diversidade e expressão diferencial de nodulinas precoces no transcriptoma de Stylosanthes scabra Vogel submetida a estresse abiótico

Abstract

New advances in technologies related to omics favored the identification of signaling mechanisms that regulate plant responses to stress. Nodulation and the ability to fix attach in association with bacteria of the genus Rhizobium spp. May determine plants survival in adverse environments. Among the several classes of genes that act under stress, the nodulins deserve mentioning, as host genes expressed during the nodulation process, being also associated with nodule functioning. Recent studies report that Stylosanthes scabra Vogel has been widely used as forage, presenting high tolerance to environments with poor soils and low water availability. The present project aimed to evaluate the response mechanisms used by S. scabra under abiotic stress (watering suppression), specifically the differential gene expression of early nodulins at different moments after the onset of stress. For this purpose, a selection of seed-sequences was performed, corresponding to cured angiosperm nodulin coding genes available in databases and in the literature. Selected nodulin seed sequences were aligned via tBLASTn against S. scabra transcriptome to select candidates for structural characterization and expression validation. To evaluate the structural diversity, phenological trees were generated. In parallel, the in silico expression profile of the early nodulins was evaluated, and primers were designed for validation of their expression. Two groups of early nodulins have been detected: ENOD and NIN, both exhibiting two conserved domains. For both groups it was possible to identify different conserved residues. Prediction of subcellular localization indicated that ENOD transcripts are associated with the cell membrane, whereas most NIN transcripts were addressed to the nucleus. Regarding the expression profile, 33 ENOD transcripts presented statistically supported data, 16 of them induced and 17 repressed. For NIN, of the total of 55 that presented valid expression, 21 were presented as inductees and 34 as repressed. From the data presented here and considering the agronomic importance of S. scabra, the relevance of the study is noteworthy, with modulated candidate transcripts that have potential for validation studies, besides helping to understand the molecular mechanisms associated with nodulation under stress conditions.