Relationship between Upper Lateral Sinus Formation and VvNAC21/22-like Expression in Grapevine Leaves

Abstract

Grapevine leaf has three unique sinuses. This study examined the relationship between the formation of the upper lateral sinus and the expression of VvNAC21/22-like, a member of grape NAC transcription factor family. VvNAC21/22-like expression was not upregulated in young leaves of all the cultivars tested and in mature leaves of cultivars having shallow sinuses but was abundant in mature leaves of cultivars having deep sinuses. Simple linear regression analysis demonstrated that in mature leaves, VvNAC21/22-like expression, but not VvNAC1, VvCUC2, and VvCUC3 expression, showed strong positive correlation with the depth of upper lateral sinus, suggesting that the increase in VvNAC21/22-like expression at the late stage of leaf maturation was related to the formation of deep upper lateral sinus in grapevine leaves. VvNAC21/22-like mRNAs were distributed in the upper and lower lateral sinuses of grapevine leaves. From these results, we hypothesize that VvNAC21/22-like plays a role in the formation of the upper lateral sinus in grapevine leaves. The findings indicate that sinuses in grapevine leaves may serve as a breeding target to enhance adaptation to environmental conditions.