GRAS family transcription factor FaSCL8 regulates <i>FaVPT1</i> expression mediating phosphate accumulation and strawberry fruit ripening
Zhenzhen Zheng, Yanjun Zhang, Yongqiang Gao, Yuanyue Shen, Yun Huang
Abstract
Strawberry is an extensively planted horticulture crop with multiple economic values. Vacuolar phosphate transporter (FaVPT1) can promote phosphate and sugar accumulation and improve strawberry fruit quality, however, its transcription regulatory mechanism remains unknown. Here, we report a GRAS superfamily transcription factor (TF) SCARECROW-LIKE8 (FaSCL8) which regulates <italic>FaVPT1</italic> expression to control strawberry fruit ripening and quality. The promoter of <italic>FaVPT1</italic> was used as a bait to screen the octoploid strawberry cDNA library by yeast one hybrid to obtain the candidate TFs including FaSCL8. FaSCL8 was located in the nucleus and was mainly expressed in fruit, its expression level was increased rapidly during ripening, and induced by exogenous phytohormones including ABA, GA, IAA, and ethylene, as well as sucrose. FaSCL8 can directly combine with the <italic>FaVPT1</italic> promoter and regulate its expression <italic>in vitro</italic> and <italic>in</italic> <italic>vivo</italic>. The results of Agrobacterium-mediated transient infection of strawberry fruits showed that overexpression of <italic>FaSCL8</italic> could increase soluble sugar, anthocyanin, and phosphorus content, promoting fruit ripening, while decreasing expression of <italic>FaSCL8</italic> showed the opposite phenotype. The expression levels of fruit ripening and quality-related genes including <italic>FaVPT1</italic>, were improved in the over-expressed fruits of <italic>FaSCL8</italic>, while receded in the <italic>FaSCL8</italic>-silenced fruits<italic>.</italic> In conclusion, this study found that FaSCL8 can regulate <italic>FaVPT1</italic> expression to improve phosphorus and sugar accumulation in strawberry fruits and promote fruit ripening, providing a new regulation mechanism of strawberry fruit ripening by phosphorus, a macroelement key to fruit quality improvement.