Genome-Wide Analysis of Phaseolus vulgaris L. miR172 Gene Family Members Under Heavy Metal Stress

Background: Phaseolus vulgaris L. are a vital source of protein, vitamins, and minerals, significantly addressing nutritional deficiencies. P. vulgaris, like other plant species, demonstrate considerable susceptibility to heavy metal stress, a significant environmental challenge. miRNAs and their target genes play a crucial role in enabling plant responses to stress. In this study, the role of miR172 gene family, which is essential for growth and development and is among the first miRNAs identified in plants, under heavy metal stress in bean plants was investigated. By employing both bioinformatics and experimental methods, we sought to gain insights into its regulatory mechanisms and possible roles in enhancing stress tolerance. Results: Bioinformatics analysis identified 6 miR172 genes located on 5 different chromosomes in the P. vulgaris genome. The precursor sequences of Pvul-miR172 exhibited a characteristic root-loop structure, and the 19 nucleotide mature sequences were conserved across various species, categorizing them into three distinct phylogenetic classes. Elements responsive to stress were identified in the promoter regions of Pvul-miR172. GO analysis revealed that eight target genes associated with Pvul-miR172 are involved in carrier activity and binding, crucial for stress response. Measured parameters included root and shoot length, cell membrane integrity, relative water content, and chlorophyll levels in two bean genotypes. Exposure to heavy metal stress increased antioxidant enzyme activity and elevated proline, H2O2, and MDA levels. The analysis of expression profiles for Pvul-miR172s and their target genes under heavy metal stress revealed diverse regulatory patterns. PCA highlighted both positive and negative associations between Pvul-miR172s and their target genes. The findings suggest that Pvul-miR172s contribute to increased tolerance to heavy metal stress, with effects differing by genotype. Conclusions: The findings of this study demonstrate that Pvul-miR172s play a vital role in regulating common beans responses to heavy metal stress through interactions with target genes. The conserved features of miR172, coupled with its stress-related cis-acting elements and regulatory effects on target genes, highlight its potential in enhancing stress tolerance. This study elucidates the molecular mechanisms underlying heavy metal stress tolerance, offering potential strategies for developing resilient crop varieties.