GRAS family transcription factor FaSCL8 regulates FaVPT1 expression mediating phosphate accumulation and strawberry fruit ripening

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 FaVPT1 expression to control strawberry fruit ripening and quality. The promoter of FaVPT1 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 FaVPT1 promoter and regulate its expression in vitro and in vivo. The results of Agrobacterium-mediated transient infection of strawberry fruits showed that overexpression of FaSCL8 could increase soluble sugar, anthocyanin, and phosphorus content, promoting fruit ripening, while decreasing expression of FaSCL8 showed the opposite phenotype. The expression levels of fruit ripening and quality-related genes including FaVPT1, were improved in the over-expressed fruits of FaSCL8, while receded in the FaSCL8-silenced fruits. In conclusion, this study found that FaSCL8 can regulate FaVPT1 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.

Keywords

• strawberry
• fascl8
• favpt1
• phosphate accumulation
• fruit ripening