The C2H2 zinc‐finger protein SlZF3 regulates AsA synthesis and salt tolerance by interacting with CSN5B

Summary Abiotic stresses are a major cause of crop loss. Ascorbic acid (AsA) promotes stress tolerance by scavenging reactive oxygen species ( ROS ), which accumulate when plants experience abiotic stress. Although the biosynthesis and metabolism of AsA are well established, the genes that regulate these pathways remain largely unexplored. Here, we report on a novel regulatory gene from tomato ( Solanum lycopersicum ) named Sl ZF 3 that encodes a Cys2/His2‐type zinc‐finger protein with an EAR repression domain. The expression of Sl ZF 3 was rapidly induced by NaCl treatments. The overexpression of Sl ZF 3 significantly increased the levels of AsA in tomato and Arabidopsis . Consequently, the AsA‐mediated ROS ‐scavenging capacity of the Sl ZF 3 ‐overexpressing plants was increased, which enhanced the salt tolerance of these plants. Protein–protein interaction assays demonstrated that Sl ZF 3 directly binds CSN 5B, a key component of the COP 9 signalosome. This interaction inhibited the binding of CSN 5B to VTC 1, a GDP ‐mannose pyrophosphorylase that contributes to AsA biosynthesis. We found that the EAR domain promoted the stability of Sl ZF 3 but was not required for the interaction between Sl ZF 3 and CSN 5B. Our findings indicate that Sl ZF 3 simultaneously promotes the accumulation of AsA and enhances plant salt‐stress tolerance.