Genome-wide Identification and Characterization of the LRX Gene Family in Grapevine (Vitis vinifera L.) and Functional Characterization of VvLRX7 in Plant Salt Response

Background Leucine-rich repeat (LRR) extensins (LRXs), cell wall-localized chimeric extensin proteins, are essential for the development of plants and in their stress resistance. Despite their significance, an extensive genome-wide analysis of the LRX gene family in grapevine ( Vitis vinifera L.) is lacking. Results We here detected 14 grapevine LRX genes and classified them into four groups through phylogenetic analysis. Their physiological and biochemical properties and gene/protein structures were also analyzed. According to synteny analysis, the expansion of the grapevine LRX gene family has been appreciably affected by tandem and segmental duplications. On investigating tissue-specific expression profiles and cis-regulatory elements, VvLRXs were found to be the comprehensive regulators of grapevine growth and response to environmental stresses. Salt stress treatments induced the expression of several VvLRX s, and VvLRX7 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. Conclusion This study has provided a general understanding of the characteristics and evolution of the LRX gene family in grapevine. And it has been demonstrated that VvLRX7 may be key regulator in plant salt response. This provides a basis for future studies of the function of grapevine LRXs and the improvement of salt stress tolerance in grapevine.