Genome-Wide Analysis of Late Embryogenesis Abundant Protein Gene Family in Vigna Species and Expression of VrLEA Encoding Genes in Vigna glabrescens Reveal Its Role in Heat Tolerance

Abstract

Late embryogenesis abundant (LEA) proteins are identified in many crops for their response and role in adaptation to various abiotic stresses, such as drought, salinity, and temperature. The <i>LEA</i> genes have been studied systematically in several crops but not in <i>Vigna</i> crops. In this study, we reported the first comprehensive analysis of the <i>LEA</i> gene family in three legume species, namely, mung bean (<i>Vigna radiata</i>), adzuki bean (<i>Vigna angularis</i>), and cowpea (<i>Vigna unguiculata</i>), and the cross-species expression of <i>VrLEA</i> genes in a wild tetraploid species, <i>Vigna glabrescens</i>. A total of 201 <i>LEA</i> genes from three <i>Vigna</i> crops were identified harboring the LEA conserved motif. Among these 55, 64, and 82 <i>LEA</i> genes were identified in mung bean, adzuki bean, and cowpea genomes, respectively. These <i>LEA</i> genes were grouped into eight different classes. Our analysis revealed that the cowpea genome comprised all eight classes of <i>LEA</i> genes, whereas the LEA-6 class was absent in the mung bean genome. Similarly, LEA-5 and LEA-6 were absent in the adzuki bean genome. The analysis of <i>LEA</i> genes provides an insight into their structural and functional diversity in the <i>Vigna</i> genome. The genes, such as <i>VrLEA-2</i>, <i>VrLEA-40</i>, <i>VrLEA-47</i>, and <i>VrLEA-55</i>, were significantly upregulated in the heat-tolerant genotype under stress conditions indicating the basis of heat tolerance. The successful amplification and expression of <i>VrLEA</i> genes in <i>V. glabrescens</i> indicated the utility of the developed markers in mung bean improvement. The results of this study increase our understanding of <i>LEA</i> genes and provide robust candidate genes for future functional investigations and a basis for improving heat stress tolerance in <i>Vigna</i> crops.