Overexpression of LAR1 Suppresses Anthocyanin Biosynthesis by Enhancing Catechin Competition Leading to Promotion of Proanthocyanidin Pathway in Spine Grape (Vitis davidii) Cells

Proanthocyanidins (PAs) are a class of polyphenolic compounds recognized for their potent antioxidant, anti-cancer, anti-inflammatory, and cardioprotective properties. However, the production of PAs from natural sources is often limited by high costs, resource wastage, and environmental damage. In this study, we investigated the overexpression of <i>VdLAR1</i>, along with phenotypic observation, metabolite determination, light quality treatment, and RT-qPCR analysis, in spine grape cells. The results demonstrated a significant increase in the contents of proanthocyanidins and flavonoids in p<i>VdLAR1</i>-overexpressing transgenic cell lines, while anthocyanin levels showed a decreasing trend. Furthermore, the treatment with white and blue light on the T5 cell line resulted in enhanced accumulation of proanthocyanidins, catechins, and flavonoids, whereas anthocyanins and epicatechins exhibited a declining pattern. Thus, short-wavelength light promoted the accumulation of metabolites, with the proanthocyanidin content in the T5 transformed cell line reaching 2512.0 μg/g (FW) during blue light incubation. RT-qPCR analysis revealed that the key genes involved in the biosynthesis of proanthocyanidin and anthocyanin were upregulated in the transgenic spine grape cell lines, with <i>VdLAR1</i> expression increasing by several hundredfold, far surpassing the expression levels of <i>LDOX</i> and <i>ANR</i>. The <i>VdLAR1</i> overexpression markedly improved substrate competitiveness within the metabolic pathway, promoting catechin biosynthesis while inhibiting the production of epicatechins and anthocyanins. This finding provides compelling evidence that <i>LAR1</i> is a crucial gene for catechin biosynthesis. This research establishes both theoretical and practical foundations for the regulation and development of natural proanthocyanidins, addressing issues related to high costs, safety concerns, resource wastage, and environmental damage associated with their production.