A CCAAT-binding factor, SlNFYA10, negatively regulates ascorbate accumulation by modulating the d-mannose/l-galactose pathway in tomato

Weifang Chen,Yuyang Zhang,Tixu Hu,Bing Wang,Fangman Li,Ying Wang,Lei Yuan,Jiaming Li,Genzhong Liu,Zhibiao Ye,Jie Ye

doi:10.1038/s41438-020-00418-6

Abstract

Ascorbic acid (AsA), an important antioxidant and growth regulator, and it is essential for plant development and human health. Specifically, humans have to acquire AsA from dietary sources due to their inability to synthesize it. The AsA biosynthesis pathway in plants has been elucidated, but its regulatory mechanism remains largely unknown. In this report, we biochemically identified a CCAAT-box transcription factor (SlNFYA10) that can bind to the promoter of SlGME1, which encodes GDP-Man-3’,5’-epimerase, a pivotal enzyme in the d-mannose/l-galactose pathway. Importantly, SlNFYA10 simultaneously binds to the promoter of SlGGP1, a downstream gene of SlGME1 in the d-mannose/l-galactose pathway. Binding assays in yeast and functional analyses in plants have confirmed that SlNFYA10 exerts a negative effect on the expression of both SlGME1 and SlGGP1. Transgenic tomato lines overexpressing SlNFYA10 show decreased levels of SlGME1 and SlGGP1 abundance and AsA concentration in their leaves and fruits, accompanied by enhanced sensitivity to oxidative stress. Overall, SlNFYA10 is the first CCAAT-binding factor identified to date to negatively regulate the AsA biosynthetic pathway at multiple sites and modulate plant responses to oxidative stress.

Highlights

Ascorbic acid (AsA, referred to as vitamin C)contributes to nutritional quality and stress responses in plants and has attracted increased amounts of attention
We used the promoter of GME1 to perform a yeast onehybrid assay in an equalized tomato complementary DNA (cDNA) library comprising various tissues of roots, leaves, flowers, and fruits at different stages to identify the candidate proteins binding to the promoter of GME1
Among the candidate binding proteins, the only annotated transcription factor, a CCAAT-box transcription factor (Solyc01g006930.2) that belong to the NFYA family and is a subunit of the NF-Y complex, was further investigated

Summary

Introduction

Contributes to nutritional quality and stress responses in plants and has attracted increased amounts of attention. AsA can remove reactive oxygen species produced by photosynthesis, respiration, biological stress, Chen et al Horticulture Research (2020)7:200 phosphatase (GPP)[11], L-Gal dehydrogenase (GalDH)[12], and L-galactono-1,4-lactone dehydrogenase (GLDH)[13]. Overexpression of GME1 and GME2 could increase the AsA content, while knockdown of either GME gene decreased the AsA content[16]. Simultaneous suppression of the GME1 and GME2 genes by RNA interference (RNAi) could reduce the AsA content by 40–60%, with increasing cell wall mannose content and fragility[17]. Suppressed expression of GME1 or GME2 separately revealed different functions in cell wall synthesis[18], suggesting the divergence of functions of GME family members

Methods

Results

Conclusion