| ‘Cabernet Sauvignon’(Vitis vinifera L.)is a typical Eurasian late-ripening wine grape variety,with many seeds and thick skin,and plenty of phenolic substances,which have the potential to produce highquality wines.In recent years,the wine producing area of the eastern foothills of Helan Mountain in Ningxia has developed rapidly,and the cultivation area of’Cabernet Sauvignon’ grapes has increased year by year,but with the increase of atmospheric CO2 concentration,extreme high temperature weather has frequently appeared,which inhibits the growth and development of grapes,affecting fruit coloration and wine quality.Exogenous brassinolide(EBR)can effectively alleviate the damage caused by high temperature to plants,improve the content of anthocyanins and fruit quality,therefore,in this study,’Cabernet Sauvignon’ grape was used as the test material,and MRM-2420 infrared radiation heater was used one week before veraison(about 49 days after flowering)for high-temperature stress treatment,set 5±0.5℃ higher than the natural temperature,and sprayed 0.6 mg·L-1 EBR,determination of anthocyanins,total sugars and related qualities,selection of fruits in the middle stage of veraison(about 70 days after flowering)for transcriptome sequencing,the effect of EBR on anthocyanin synthesis under high temperature stress was elaborated from the molecular level,and the results were as follows:1.Effects of EBR treatment on anthocyanin composition and content of grape berries under high temperature stress.Under high temperature stress,the total anthocyanin content of grape berries was significantly reduced,and the berries were 0.977 mg·g-1 lower than those in the control group when ripe,and the total anthocyanin content at ripening was 0.1 86 mg·g-1 higher than that under high temperature stress after EBR spraying.Under high temperature stress,there was no significant difference between anthocyanin components and after EBR spraying,and the content of Delphinidin-3-O-acelylglucoside in the mature stage was significantly increased,which was 0.285 mg·g-1 higher than that of the control group,and the content of Malvidin-3-O-glucoside was reduced.After EBR spraying,the contents of Peonidin3-O-glucoside and Malvidin-3-O-glucoside were significantly higher than those in the high-temperature stress group,with 0.155 mg·g-1 and 0.436 mg·g-1,respectively.2.Effects of EBR treatment on endogenous hormones and quality of grape fruits under high temperature stress.After EBR spraying,the sugar accumulation law was similar to that of the control group,but the total sugar content in the ripening period was slightly lower than that of the control group,and the titratable acid content was 0.84%higher than that of the control group.Under high temperature stress,auxin,salicylic acid and abscisic acid were negatively correlated with total anthocyanins,and after EBR spraying,auxin,salicylic acid and abscisic acid were negatively correlated with total anthocyanin content,with correlation coefficients of-0.917,-0.497 and-0.462,and brassinolide was positively correlated with total anthocyanin content,with a correlation coefficient of 0.246.Under high temperature stress,brassinolide was negatively correlated with the contents of Delphinidin-3-O-acelylglucoside and Petunidin-3-O-glucoside,and positively correlated with the contents of anthocyanins of the other three monomers.After spraying EBR,it was positively correlated with the content of anthocyanins in five monomers.3.Effects of EBR treatment on fruit transcription level under high temperature stress.Under high temperature stress,there were 1721 differential genes,including 1229 upregulated genes and 492 downregulated genes,and 977 differential genes after spraying EBR,of which 690 were up-regulated and 287 were down-regulated.GO and KEGG enrichment analysis showed that 10 genes related to starch-sucrose metabolism pathway were upregulated and 4 genes of this pathway were downregulated at high temperature.After EBR spraying,the expression of genes related to the starch-sucrose metabolic pathway decreased but was higher than that in the control group.In the phenylalanine metabolic pathway,the expression of synthetic lignin genes such as CST,C3H,CQT and CCoAOMT was upregulated by high temperature stress,and the expression of genes related to lignin synthesis decreased after EBR spraying,but it was higher than that in the control group.In addition,high temperature stress significantly increased the expressions of genes LDOX related to anthocyanin synthesis,LAR related to catechin synthesis and F3H related to dihydromyricetin synthesis during veraison,and decreased the expressions of related genes after spraying EBR. |
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