Pepper kinase CaSNF1 phosphorylates CaHD-ZIP to boost cold tolerance

Cold stress severely restricts the growth and productivity of pepper (Capsicum annuum L.) by disrupting cellular homeostasis and inducing oxidative damage. Although HD-ZIP transcription factors are known to play important roles in plant responses to abiotic stress, the molecular mechanisms that regulate their function during cold stress have remained largely unknown. A new study published in Theoretical and Applied Genetics characterizes a pepper HD-ZIP transcription factor, CaHD-ZIP, and reports that it is a nuclear-localized, cold-responsive protein that positively contributes to cold stress tolerance.

To probe how CaHD-ZIP itself is regulated, the researchers carried out a yeast two-hybrid screen, which identified the sucrose non-fermenting 1-related protein kinase CaSNF1 as a previously unrecognized interacting partner of CaHD-ZIP. The interaction was confirmed by three independent approaches: yeast two-hybrid assays, luciferase complementation imaging, and bimolecular fluorescence complementation. The BiFC experiments indicated that the interaction occurs predominantly in the nucleus, consistent with CaHD-ZIP’s nuclear localization.

The team then sought biochemical evidence for a functional regulatory relationship. In vitro phosphorylation analysis demonstrated that CaSNF1 directly phosphorylates CaHD-ZIP, showing that the physical interaction between the two proteins is accompanied by a direct enzymatic modification. This establishes CaSNF1 as a CaHD-ZIP-interacting kinase and points to a potential CaSNF1–CaHD-ZIP regulatory module involved in pepper cold stress adaptation.

Complementary loss- and gain-of-function analyses supported a positive role for CaSNF1 in cold tolerance. Virus-induced gene silencing and transient overexpression in pepper, together with stable overexpression in Arabidopsis, showed that silencing CaSNF1 increased oxidative damage, impaired antioxidant enzyme activities, and suppressed the expression of antioxidant and cold-responsive genes. Overexpression produced the opposite effects and significantly enhanced cold tolerance in the experimental systems used.

According to the authors, these findings advance understanding of the molecular mechanisms underlying pepper cold tolerance and suggest potential genetic targets for improving cold resilience in pepper and other Solanaceae crops. The work was published online on 23 October 2026 as article number 311 in volume 139 of the journal, with Ikram Ullah, Yingping Pei, Menghan Wang, Altaf Hussain, Jiangbai Guo, Huafeng Zhang and Rugang Chen listed among the authors.

Subject of Research: A CaSNF1–CaHD-ZIP regulatory module involved in cold stress tolerance in pepper

Article Title: CaSNF1 interacts with and phosphorylates CaHD-ZIP to enhance cold tolerance in pepper

Article References: Ullah, I., Pei, Y., Wang, M., Hussain, A., Guo, J., Zhang, H., & Chen, R. (2026). CaSNF1 interacts with and phosphorylates CaHD-ZIP to enhance cold tolerance in pepper. Theoretical and Applied Genetics, 139(11), Article 311. https://doi.org/10.1007/s00122-026-05413-4

Image Credits: AI Generated

DOI: 10.1007/s00122-026-05413-4

Keywords: pepper, cold stress, CaSNF1, CaHD-ZIP, phosphorylation, transcription factor, abiotic stress, antioxidant, Arabidopsis, Capsicum annuum, plant molecular biology, gene silencing