Light Quality Modulates Growth, Triggers Differential Accumulation of Phenolic Compounds, and Changes the Total Antioxidant Capacity in the Red Callus of Vitis davidii.

Light quality is one of the key elicitors that directly affect plant cell growth and biosynthesis of secondary metabolites. In this study, the red callus of spine grape was cultured under nine light qualities (namely, dark, white, red, yellow, blue, green, purple, warm-yellow, and warm-white light). The effects of different light qualities were studied on callus growth, accumulation of phenolic compounds, and total antioxidant capacity of the red callus of spine grape. The results showed that blue and purple light induced increased red coloration in the callus, whereas yellow light induced the greatest callus proliferation. Among all of the light quality treatments, darkness treatment downregulated the contents of phenolic compounds, whereas blue light was the treatment most conducive to the accumulation of total phenolics. White, blue, and purple light induced increased anthocyanin accumulation. Mixed-wavelength light was beneficial to the accumulation of flavonoids. Blue and purple light were conducive to the accumulation of proanthocyanidins. A further study showed that cyanidin 3-glucoside (Cy3G) and peonidin 3-glucoside (P3G) were the main anthocyanin components in the callus, and blue, purple, and white light treatments promoted their accumulation, whereas flavan-3-ols and flavonols were the main components of non-anthocyanin phenolics, and their accumulation changed in response to not only light quality but also culture duration. The total antioxidant capacity of the callus cultures changed significantly in response to different light qualities. These results will provide evidence for an abiotic elicitor strategy to stimulate callus growth and enhance the accumulation of the main phenolic compounds in the red callus of spine grape.

The Single-Stranded DNA-Binding Gene Whirly (Why1) with a Strong Pathogen-Induced Promoter from Vitis pseudoreticulata Enhances Resistance to Phytophthora capsici.

Vitis vinifera plants are disease-susceptible while Vitis pseudoreticulata plants are disease-resistant; however, the molecular mechanism remains unclear. In this study, the single-stranded DNA- and RNA-binding protein gene Whirly (VvWhy1 and VpWhy1) were cloned from V. vinifera "Cabernet Sauvignon" and V. pseudoreticulata "HD1". VvWhy1 and VpWhy1 promoter sequences (pVv and pVp) were also isolated; however, the identity of the promoter sequences was far lower than that between the Why1 coding sequences (CDSs). Both Why1 gene sequences had seven exons and six introns, and they had a C-terminal Whirly conserved domain and N-terminal chloroplast transit peptide, which was then verified to be chloroplast localization. Transcriptional expression showed that VpWhy1 was strongly induced by Plasmopara viticola, while VvWhy1 showed a low expression level. Further, the GUS activity indicated pVp had high activity involved in response to Phytophthora capsici infection. In addition, Nicotiana benthamiana transiently expressing pVp::VvWhy1 and pVp::VpWhy1 enhanced the P. capsici resistance. Moreover, Why1, PR1 and PR10 were upregulated in pVp transgenic N. benthamiana leaves. This research presented a novel insight into disease resistance mechanism that pVp promoted the transcription of Why1, which subsequently regulated the expression of PR1 and PR10, further enhancing the resistance to P. capsici.