Effects of IPT or NDGA Application on ABA Metabolism and Maturation in Grape Berries

The effects of isoprothiolane (IPT: a fungicide used to control rice blast) and nordihydroguaiaretic acid (NDGA: an inhibitor of the phytohormone abscisic acid (ABA) biosynthesis) on the maturation of “Shine Muscat” grape berries were investigated. The results showed that IPT and NDGA retarded chlorophyll degradation in the berry skin. Transcriptional profiling revealed that 2218 genes in the grapes treated with IPT and 2270 genes in those treated with NDGA were differentially expressed compared to the untreated control grapes at 70 days after full bloom (DAFB). IPT or NDGA application regulated the expression of genes involved in ABA, auxin, and ethylene metabolism. MapMan analysis and qRT-PCR validation showed that the expression levels of VvNCED1, VvCYP707A1, VvAAO4 , and VvGEM-like genes in the ABA metabolic pathway were negatively regulated by IPT and NDGA treatment at 70 DAFB. Moreover, IPT and NDGA treatment inhibited glucose accumulation via the VvSUS, VvAI, VvHT genes in the sugar metabolic pathway. In addition, IPT and NDGA treatment delayed ( E )-2-hexenal and hexanol productions, and down-regulated aroma metabolic pathway genes such as VvLOX, VvADH, VvGPPS, and VvTPS . These results suggest that IPT and NDGA influence chlorophyll degradation, ABA accumulation, and sugar and aroma volatile syntheses in the maturation process.