Transcription and phosphorylation of CATALASE2 contribute to cold stress tolerance in Hevea brasiliensis

Despite the economic importance of the rubber tree (Hevea brasiliensis) and its sensitivity to cold stress, the molecular mechanisms that govern its cold response are still largely unknown. Here, we identified H. brasiliensis CATALASE2 (HbCAT2) as a factor associated with cold tolerance in this species, likely through reducing excess H₂O₂. Cold stress significantly induced HbCAT2 transcription and catalase activity in H. brasiliensis, and overexpression of HbCAT2 in both H. brasiliensis and Arabidopsis enhanced cold tolerance and reduced H₂O₂ accumulation. Furthermore, we found that HbCBF1, a key transcription factor in plant cold signaling, could directly bind to and activate HbCAT2, and overexpression of HbCAT2 was able to alleviate the cold hypersensitivity of the Arabidopsis cbf123 triple mutant. Additionally, the protein kinase HbSnRK2.6A interacted with and phosphorylated HbCAT2 to stimulate its catalase activity. Genetic evidence showed that HbSnRK2.6A-mediated cold tolerance is associated with CAT2 function. Together, our findings are consistent with a dual regulatory module in which HbCBF1-mediated HbCAT2 transcription and HbSnRK2.6A-mediated phosphorylation of HbCAT2 may contribute to enhancing cold tolerance by preventing H₂O₂ overaccumulation in H. brasiliensis.