A C2H2‐type zinc finger protein ZAT12 of Poncirus trifoliata acts downstream of CBF1 to regulate cold tolerance.

SUMMARY: The Cys2/His2 (C2H2)‐type zinc finger family has been reported to regulate multiple aspects of plant development and abiotic stress response. However, the role of C2H2‐type zinc finger proteins in cold tolerance remains largely unclear. Through RNA‐sequence analysis, a cold‐responsive zinc finger protein, named as PtrZAT12, was identified and isolated from trifoliate orange (Poncirus trifoliata L. Raf.), a cold‐hardy plant closely related to citrus. Furthermore, we found that PtrZAT12 was markedly induced by various abiotic stresses, especially cold stress. PtrZAT12 is a nuclear protein, and physiological analysis suggests that overexpression of PtrZAT12 conferred enhanced cold tolerance in transgenic tobacco (Nicotiana tabacum) plants, while knockdown of PtrZAT12 by virus‐induced gene silencing (VIGS) increased the cold sensitivity of trifoliate orange and repressed expression of genes involved in stress tolerance. The promoter of PtrZAT12 harbors a DRE/CRT cis‐acting element, which was verified to be specifically bound by PtrCBF1 (Poncirus trifoliata C‐repeat BINDING FACTOR1). VIGS‐mediated silencing of PtrCBF1 reduced the relative expression levels of PtrZAT12 and decreased the cold resistance of trifoliate orange. Based on these results, we propose that PtrZAT12 is a direct target of CBF1 and plays a positive role in modulation of cold stress tolerance. The knowledge gains new insight into a regulatory module composed of CBF1‐ZAT12 in response to cold stress and advances our understanding of cold stress response in plants. Significance Statement: 1. PtrZAT12 functions in cold tolerance and regulates COR genes. 2. PtrCBF1 regulates PtrZAT12 expression by binding to the DRE/CRT motif in the gene promoter. [ABSTRACT FROM AUTHOR]