Genome-wide identification and characterization of the LRX gene family in grapevine (Vitis vinifera L.) and functional characterization of VvLRX7 in plant salt response

Leucine-rich repeat (LRR) extensins (LRXs), which are cell wall-localized chimeric extensin proteins, are essential for the development of plants and their resistance to stress. Despite the significance of these genes, an extensive genome-wide analysis of the LRX gene family in grapevine (Vitis vinifera L.) is lacking. We here detected 14 grapevine LRX genes and classified them into four groups through phylogenetic analysis. Then, their physiological and biochemical properties and gene/protein structures were analyzed. According to synteny analysis, tandem and segmental duplications have appreciably affected the expansion of the grapevine LRX gene family. On investigating tissue-specific expression profiles and cis-regulatory elements, we observed that VvLRXs likely serve as regulators of both the growth of grapevines and their responses to various environmental stresses. Salt stress treatments induced the expression of several VvLRXs, and VvLRX7 expression was the most significantly upregulated. Furthermore, VvLRX7 expression was positively correlated with the salt tolerance of grape rootstocks. VvLRX7 overexpression in Arabidopsis markedly enhanced its salt tolerance. This study provides a general understanding of the characteristics and evolution of the LRX gene family in grapevine. VvLRX7 may function as a positive regulator of plant's response to salt stress. These findings offer a basis for future studies on the function of grapevine LRXs and their role in improving salt stress tolerance in grapevine.