Caracterização in silico e expressão de genes relacionados à prolina em feijão sob condições de estresse abióticos

Abstract

The common bean (Phaseolus vulgaris L.) is a crop of significant socioeconomic importance in Brazil, with production distributed across multiple states and seasonal cycles. This legume faces substantial soil and climate challenges, particularly abiotic stresses such as water deficit and salinity, which are limiting factors that reduce productivity. In this context, investigating contrasting genotypes for tolerance to these stresses, such as BAT 477 (tolerant) and Pérola (susceptible), represents a fundamental strategy for developing cultivars adapted to adverse environmental conditions. This study aimed to identify in silico and molecularly characterize the genes encoding the enzyme Δ¹-pyrroline-5-carboxylate synthetase (P5CS) and proline transporters (ProT) in P. vulgaris L., key components in the biosynthesis and translocation of proline, a compatible osmolyte with a crucial role in osmoregulation and cellular protection mechanisms under stress conditions. Through comparative genomic analyses, four P5CS genes and two ProT genes were identified in the common bean genome. The PvP5CS genes are distributed across chromosomes 1, 8 (containing two genes), and 10, indicating segmental duplication events throughout the species' evolutionary history. Phylogenetic analyses revealed significant genomic conservation among the P5CS genes of P. vulgaris L., Arabidopsis thaliana, and Oryza sativa. Regarding transcriptional profiles, PvP5CS3 showed the highest expression in all developed tissues, with particular abundance in nodules and roots, while PvP5CS2 exhibited reduced transcriptional levels in all vegetative organs. The ProT transporters, located on chromosomes 1 and 8, displayed preferential expression in floral tissues. Physiological assays under controlled conditions revealed contrasting patterns of proline accumulation between the tested genotypes in response to different stresses. Under saline stress (NaCl), the Pérola cultivar showed significantly higher proline accumulation compared to BAT 477, especially after prolonged exposure (12 days) and high NaCl concentrations, reaching approximately 55 μmol/g FW compared to only 7 μmol/g FW in BAT 477. Conversely, under osmotic stress induced by polyethylene glycol (PEG 6000), an opposite behavior was observed, with BAT 477 exhibiting greater proline accumulation capacity (8 μmol/g FW) compared to Pérola (3.5 μmol/g FW). Through in silico analyses, the expression profiles of these genes were identified in leaves of two bean genotypes (BAT 477 and Pérola) under saline and water stress. The genes PvP5CS1, PvP5CS3, and PvP5CS4 showed significantly lower gene expression in different vegetative tissues (in silico). Saline stress (osmotic), characterized by high salt concentrations, differs from water stress, which can result from both water deficiency and excess. These results suggest the existence of distinct regulatory mechanisms and genotype-specific responses in proline biosynthesis and transport under different abiotic stresses in P. vulgaris L.. The elucidation of these molecular mechanisms offers promising prospects for genetic improvement, supporting the development of cultivars with greater yield stability under adverse environmental conditions, thus contributing to food security and agricultural sustainability.