Grape production in southern China suffers great loss due to various environmental stresses. To understand the mechanism of how the grape plants respond to these stresses is an active area of research in developing cultivation techniques. Plant stress resistance is known to rely on special proteins. Amongst them, DnaJ protein (HSP40) serves as co-chaperones of HSP70, playing crucial roles in various stress response. However, the DnaJ proteins encoded by the DnaJ gene family in Vitis vinifera L. have not been fully described yet. In this study, we identified 78 VvDnaJs in the grape genome that can be classified into three groups—namely, DJA, DJB, and DJC. To reveal the evolutionary and stress response mechanisms for the VvDnaJ gene family, their evolutionary and expression patterns were analyzed using the bioinformatic approach and qRT-PCR. We found that the members in the same group exhibited a similar gene structure and protein domain organization. Gene duplication analysis demonstrated that segmental and tandem duplication may not be the dominant pathway of gene expansion in the VvDnaJ gene family. Codon usage pattern analysis showed that the codon usage pattern of VvDnaJs differs obviously from the monocotyledon counterparts. Tissue-specific analysis revealed that 12 VvDnaJs present a distinct expression profile, implying their distinct roles in various tissues. Cis-acting element analysis showed that almost all VvDnaJs contained the elements responsive to either hormones or stresses. Therefore, the expression levels of VvDnaJs subjected to exogenous hormone applications and stress treatments were determined, and we found that VvDnaJs were sensitive to hormone treatments and shade, salt, and heat stresses, especially VIT_00s0324g00040. The findings of this study could provide comprehensive information for the further investigation on the genetics and protein functions of the DnaJ gene family in grape.

Aroma is one of the most important indicators of grape quality. Girdling and foliar fertilization with K (K₂O) are common agronomic practices applied to improve berry quality in grape production. However, little is known about its effect on the accumulation and biosynthesis of the entire aromatic profile. Our study was aimed to explore the influences of girdling and foliar fertilization with K (alone or in combination) on the general properties, phenolic composition, volatile free aroma compounds, spatial and temporal expression of terpene-related genes and sensory properties in ‘Hanxiangmi’ table grape. In this study, we found that girdling and foliar fertilization with K (alone or in combination) facilitated fruit enlargement and increased the accumulation of phenolic compounds in skin. The combination treatment of girdling and foliar fertilization with K significantly promoted the concentrations of total soluble solids (TSS) in the pulp and proanthocyanidins in the berry skin, and had a lower titratable acidity (TA) compared to those of the control. In contrast, girdling treatment alone increased the concentrations of titratable acidity. Volatile free aroma composition analysis revealed that the combination treatment increased the volatile compounds and concentrations significantly, most notably in terpenes, such as nerol, citronellol and linalool. Spatial and temporal expression analysis showed that the expression level of VvDXS was significantly correlated with linalool and total terpenes concentrations, as a result of which, we speculated that VvDXS is the candidate gene for the regulation of important grape terpenes. We hope that our results can direct farmers to better apply girdling and foliar fertilization with K in grape production.

With the frequent occurrence of extreme natural disasters, unfavorable growth environment is a common phenomenon in the life cycle of plants. In recent years, universal stress proteins (USPs) have attracted extensive attention in the field of plant science for their expression patterns and functional analysis. However, the characterization of the USP family remains unclear in grape. In this study, we identified 30 VvUSPs in the grape genome, which could be divided into three classes according to their encoded protein sequences, and this classification was reflected by the distribution of conserved motifs. Gene duplication analysis demonstrated that segmental duplication was an important pathway in the expansion of the VvUSP family. The expression patterns of 12 VvUSPs were significantly different between tissues, implying they had different functions in various tissues. Cis-acting element and expression analysis showed that most of the promoter regions of VvUSPs contained sequences responsive to hormones and stress elements, especially the promoter region of VIT_16s0013g01920. In conclusion, our findings provide comprehensive information for the further investigation of the genetics and protein functions of the USP gene family in grape.

Suboptimal light stress in grapevines is increasing worldwide with the spread of grapevine cultivation, which can affect grapevine physiology and productivity, such as in Southern China. Abscisic acid (ABA) is an important hormone in plant adaptive responses to abiotic stress, including low light stress. However, ABA signaling pathway genes (APGs) are not well characterized in the grapevine, and little is known of their potentially mitigating role in grapevine growth under weak light stress. Our study aimed to explore the potential role of the ABA signaling pathway in the response of grapevines to suboptimal light conditions. In this study, APGs were identified in the grapevine genome, and the distribution of conserved motifs was shown to reflect their phylogenetic relationships. Gene duplication analysis indicated that segmental duplication was an important driver for gene expansion in the grapevine ABA signaling pathway. Suboptimal conditions of light were shown to seriously affect the growth of grapevine leaves and berries, with the differential regulation of APGs in the grapevine. Our study summarizes the basic characteristics of APGs in grapevine, which can now be examined further for their roles in grapevine’s response to suboptimal light conditions.