## 4 Discussion
### Principal Genes and TFs  
The chaperone protein DnaJ (HSP40) family was shown to have a unique function under heat stress in _Arabidopsis_[26]. _PCC13-62_, as a gene that encodes desiccation-related proteins (DRPs), was less highly expressed in desiccation-sensitive species when compared with desiccation-tolerant species [27]. Therefore, in our study, the different expressional patterns of the two thermal and moisture-related genes in grapes that were cultivated with different average temperatures and humidity levels could enhance existing knowledge on their functions in plant physiological processes.  
As mentioned with regard to TFs, a novel essay demonstrated that VvWRKY22 could regulate saccharide accumulation in grapes by interacting with VvSnRK1.1 or VvSnRK1.2 proteins [28]. Moreover, it was reported that saccharides in grapes were influenced by the surrounding conditions during fruit development [29]. As detected, the elongation of actual sunshine duration enhanced the accumulation of saccharides [29]. In our results, the saccharide contents in TS were higher than in US (Table 1); correspondingly, _VvWRKY22_ was highly expressed in TS at later stages. Therefore, we inferred that the high expressional pattern of _VvWRKY22_ in TS was the outcome of high light intensity and long sunshine duration, and consequently induced the accumulation of saccharides.  
Evidently, bHLH34 may bind to the promoter region of _AtPGR_ and act as a positive regulator of glucose [30]. Additionally, the upregulation of _SlbHLH95_ in tomato fruit ripening resulted in the accumulation of glutathione, soluble saccharides and starch [31]. These results, together with the finding that a higher accumulation of saccharides occurred in grapes from a region with longer sunlit time [29], indicate that bHLHs in grapes probably play a contributory role in saccharide accumulation. Hence, the long sunlit time in Turpan contributed to the high expressional value of bHLHs in TS grapes and modulated saccharide accumulation. In addition, _bHLH95_ exhibited a negative correlation (r = \(-\)0.975) with (E)-2-hexenal (Table S7), which indicated a possible relationship between the syntheses of (E)-2-hexenal and saccharides.  
In plants, _MYB_ genes are responders under abiotic stresses, such as drought and cold, and they also participate in light-sensing [32]. [PERSON] et al. detected that the expressions of three _MYB-related_ genes differed dramatically among various light and temperature applications during grape development [33]. Interestingly, the correlation results (Table S7) showed a high correlation value (r = 0.974) between _REVEILLE 1_ and decanal in TS. Moreover, _MYB-R_ possessed high correlation values with the volatiles that accumulated during fruit ripening in TS (Table S7). Thus, the expressions of _MYB-related_ genes in our study might have been enhanced by the combination of stresses from high temperature, high light intensity and low humidity in Turpan region, thus modulating the biosynthesis of volatiles. In general, aside from the previous findings on the regulatory roles of _MYB-related_ genes on anthocyanin and flavonoid biosynthesis in grapes [33], we investigated the potential regulatory roles of _MYB-related_ genes on grape volatile syntheses.  
As reported, heat or drought stress could increase the expressional levels of grape _ERF_ genes [34]. Thus, in our study, the high expressions of _ERF003_ and _ERF110_ might be induced by high temperature and low humidity. Furthermore, HSF30 in grapes might be a key regulator for heat stress and heat recovery [35], hence the two _HSFs_ selected in our study were probably stressed by high temperature and consequently upregulated. Overall, these results could enrich the regulatory function of TFs on volatile metabolism in grapes.