## 3 Results and Discussion
### Anthocyanin Profiles and Related Gene Expressions  
The anthocyanin profiles of grapes may be affected by many factors, such as variety, management, temperature, and light [17]. In the present study, the anthocyanin profiles of four Chinese wild spine grape varieties were analyzed. The identification of anthocyanins was qualitatively determined by using the standard sample malvidin-3-glucoside, and then other anthocyanin components were identified according to references, which reported that the peak sequences of nine kinds of anthocyanins were: Delphinidin-3-glucoside (Dp), Cyanidin-3-glucoside (Cy), Petunidin-3-glucoside (Pt), Peonidin-3-glucoside (Pn), Malvidin-3-glucoside (Mv), Peonidin-3-acetyl-glucoside (Pn-AG), Malvidin-3-acetyl-glucoside (Mv-AG), Peonidin-3-couamyl-glucoside (Pn-CG) and Malvidin-3-couamyl-glucose (Mv-CG) [36; 37; 38]. As the results in Table 2 show, a total of nine anthocyanin types were detected. There were no anthocyanins detected in the white spine grape (BY). Interestingly, cyanidin-3-glucoside and malvidin-3-acetyl-glucose were the most abundant anthocyanins in the other three spine grapes, while malvidin-3-glucose is the most abundant anthocyanin in _Vitis vinifera_ grapes [17]. The Mv derivative content--including malvidin-3-glucoside, malvidin-3-acetyl-glucose,  
Figure 1: Expression levels of sugar unloading-associated genes in spine grapes. Values presented are means \(\pm\) SD (\(n=3\)). _VdGAPDH_ was used as reference gene. Different letters indicate significant differences among four spine grapes using Duncan’s test (\(p<0.05\)). G2: Gaoshan #2, G4: Gaoshan #4, XZZ: Xiangzhenzhu, BY: Baiyu. and malvidin-3-coumayl-glucoside--was higher than any other kind of anthocyanin in spine grapes. The cyanidin-3-glucoside content in the spine grapes was second only to the content of malvidin-3-acetyl-glucose. The three spine grapes had a few Cy, Dp, Pt, and Pn derivatives. Conversely, the content of Cy, Dp, Pt, and Pn derivatives in _Vitis vinifera_ and _Vitis quinquangularis_ cultivars is high, while the Mv derivative content is very low [4; 25]. These results indicate that _Vitis davidii_ cultivars might have different anthocyanin component characteristics than _Vitis vinifera_ and _Vitis quinquangularis_ varieties. More research is needed to reveal the anthocyanin properties of _Vitis davidii_ cultivars. A recent study reported that some grape species native to China, including _V. davidii_ and _V. amurensis_, had higher total anthocyanin contents (TAC) than _V. vinifera_ grapes [4]. These indicated that spine wines might have similar health benefits since their anthocyanin contents were competitive with _V. vinifera_ grape wines. In the present study, we also found that the anthocyanins contents in spine grapes were significantly higher than _V. vinifera_ grapes, this might indicate that spine wines had richer anthocyanins and a more attractive color for consumers than _V. vinifera_ wines [26]. To better understand the mechanism of the varietal differences in anthocyanin profiles, the transcript levels of 10 key genes (_VdPAL_, _VdC4H_, _VdCHS_, _VdF3'H_, _VdF3'5'H_, _VdPFR_, _VdLDOX_, _VdUFGT_, _VdOMT_, and _VdGST_) involved in the anthocyanin biosynthesis pathway were analyzed. As Figure 2 shows, the expression levels of _VdPAL_, _VdC4H_, _VdCHS_, _VdF3'H_, _VdPFR_, _VdLDOX_, _VdUFGT_, _VdOMT_, and _VdGST_ genes were highest in XZZ grapes, followed by G4 grapes. The transcript level of the _VdF3'5'H_gene was the lowest among the 10 genes in all spine grape varieties. Although anthocyanin biosynthesis genes were also expressed in white varieties (BY), these levels were very low. The product of _PAL_, _C4H_, and _CHS_ acts upstream of the phenylalanine metabolic pathway, and its expressions were significantly different among grape varieties [39]. Our results also support this conclusion. The expression levels of _VdGST_ and _VdOMT_ were the highest among the 10 genes in all spine grapes, especially in XZZ grapes.