Student Perspectives on the First Day of Class.

Abstract

Anthocyanins have important physiological functions and are beneficial to the improvement of fruit quality in strawberry. Light is important for anthocyanin biosynthesis, and specific light quality was identified to promote anthocyanin accumulation in many fruits. However, research on the molecular mechanisms of anthocyanin accumulation regulated by light quality in strawberry remains limited. Here we described the effects of red- and blue-light irradiation on anthocyanin accumulation in strawberry. The results showed that blue light, rather than red light, could lead to the rapid accumulation of anthocyanins after exposure to light for 48 hours. The transcriptional levels of anthocyanin structural and regulatory genes displayed similar trend to the anthocyanin content. To investigate the mechanism of blue light-induced anthocyanin accumulation, the homologs of Arabidopsis blue light signal transduction components, including the blue light photoreceptor <i>FaCRY1</i>, an E3 ubiquitin ligase <i>FaCOP1</i> and light-responsive factor <i>FaHY5</i>, were cloned from the strawberry cultivar 'Benihoppe'. The protein-protein interaction of FaCRY1-FaCOP1-FaHY5 was revealed by yeast two-hybrid and fluorescence signal assays. Functional complementation analysis showed that overexpression of either <i>FaCOP1</i> or <i>FaHY5</i> restored the anthocyanin content and hypocotyl length in corresponding Arabidopsis mutants under blue light. Moreover, dual-luciferase assays showed that FaHY5 could increase the activity of <i>FaRAP</i> (anthocyanin transport gene) promoter and that this function relied on other, likely B-box protein FaBBX22, factors. The overexpression of <i>FaHY5</i>-<i>VP16</i> (chimeric activator form of FaHY5) and <i>FaBBX22</i> promoted the accumulation of anthocyanins in transgenic strawberry plants. Further, transcriptomic profiling indicated that the genes involved in the phenylpropanoid biosynthesis pathway were enriched in both <i>FaHY5</i>-<i>VP16-</i>OX and <i>FaBBX22</i>-OX strawberry plants. In summary, our findings provide insights into a mechanism involving the regulation of blue light-induced anthocyanin accumulation <i>via</i> a FaCRY1-FaCOP1-FaHY5 signal transduction module in strawberry.