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.

Identification of a PTC-containing DlRan transcript and its differential expression during somatic embryogenesis in Dimocarpus longan.

RAN (Ras-related nuclear protein) plays crucial roles in multiple cellular processes in yeast, animals and plants. Here we present a DlRan gene and its alternative splicing transcripts containing premature terminator codons (PTCs), identified from embryogenic cultures in longan. Multiple alignment and splicing pattern analyses indicated that DlRan-1 transcript harboring PTC was the consequence of alternative splicing. The accumulation of DlRan PTC-containing transcripts increased significantly when the embryogenic calli were treated with the translation inhibitor, cycloheximide, indicating that DlRan-1 may be targeted by NMD. The analysis of expression profiles of DlRan transcripts revealed that differential expression levels of the alternative spliced DlRan transcripts occurred during the development of embryogenic callus, globular-shaped embryos, and cotyledon-shaped embryos, respectively, in the longan somatic embryogenesis, and were in consistent with the embryo development in corresponding wild-type transcripts. The present work offers evidence to speculate that the alternatively spliced PTC-containing transcripts can be functional and may shed light on expression regulation of DlRan during development of the longan somatic embryos.