## 2 Results
### Regulation of ABA and NAA on the Biosynthesis and Accumulation of Norisoprenoids  
#### 2.2.1 Effects on Norisoprenoid Production and Related Gene Expression  
The concentration of free-form and total norisoprenoids varied among the berries of the treatments and the control (Figure 5). ABA1000 and ABA800 application were observed to markedly increase the concentration of free-form norisoprenoids in 2015 at E-L 34 and E-L 38 stages. Despite a similar pattern was observed in 2016, the difference between the control and ABA1000-treated berries were significant only at E-L 34 stage. Lower levels of total norisoprenoid were observed in ABA-treated berries than Control berries at E-L 34 and E-L 35 stages in 2015, higher levels were observed in ABA800-treated berries than Control berries at E-L 35 stage in 2016. No effects of ABA treatments on the total norisoprenoid concentration were observed at harvest (E-L 38). NAA100-treated berries showed a high level of both free-form and total norisoprenoids at E-L 38 in 2015. The total concentration of each norisoprenoid was presented in Table S2. When grape berries reached maturity (E-L 38 stage), a different response to the ABA and NAA treatments among the identified norisoprenoids was found. Higher concentrations of vitispirane A, vitispirane B and (E)-1-(2,3,6-trimethylphenyl)buta-1,3-diene (TPB) were observed in NAA-treated berries at all sampling stages. Most norisoprenoid compounds such as \(\beta\)-damascenone and \(\beta\)-ionone appeared to be significantly increased by NAA treatment in harvested berries in 2015, except for geranylacetone and 6-methyl-5-hepten-2-one (MHO). ABA800 and ABA1000 had consistent negative effects on the accumulation of vitispirane A, vitispirane B and MHO in harvested berries in both seasons. Additionally, geranylacetone concentration was not influenced by ABA treatments at E-L 38 stage, and the responses of other norisoprenoids to ABA were not consistent among the two seasons. The transcriptome analysis was conducted on the ABA1000, NAA100 and control berries collected in 2015. Concerning the genes involved in norisoprenoid biosynthesis (Figure 2B), we found that ABA treatment markedly suppressed the expression of VviLECY, VviCCD4a and VviABA-Hase at the early stage, but elevated the expression of VviCCD4b and key ABA biosynthesis-related genes including VviNCED1, VviNECD2, and VviNCED3. Expectedly, NAA treatment up-regulated the norisoprenoid biosynthesis-related genes such as VviPSY1, VviPSY2, VviPSY3, VviLECY, VviLBCY, VviZEP, VviCCD4a, and VviCCD4b, which corresponded to the increase in total concentration of norisoprenoids. Meanwhile, this treatment also suppressed the expression of VviPSY (VIT_203s0038g00450) at E-L 36 stage, three VviNCEDs at E-L 34 stage and two VviABA-Hases. The transcription of other norisoprenoid genes such as PDS, ZISO, CRTISO, LUT5/BCH, LUT1, AAO, and CCD1 were insensitive to both ABA and NAA treatments.  
Figure 4: Differentially expressed switch genes between treatments and control. The significance of differentially expressed genes was judged based on the False Discovery Rate \(\leq\) 0.01 and absolute value of log2 Ratio \(\geq\) 1. Blue and cyan boxes indicate significantly downregulated and upregulated genes in treated berries compared to the control, respectively. Genes were divided into groups (**a**–**e**) according to their different responses to the treatments.