CmCBF4 crosstalk with H2O2 signal involved in trehalose-promoted cold tolerance of melon seedlings

Cold stress severely inhibits the normal growth of melon (Cucumis melo var. makuwa Makino) seedlings. At low temperature, the moderate increase of apoplastic hydrogen peroxide (H₂O₂) level and subsequent intracellular signal transduction are important to plant cold response. Our previous studies showed that trehalose (Tre) could activate H₂O₂ signal and improve cold tolerance of melon seedlings. However, the specific mechanism is not completely clear. Here, we found that Tre-promoted C-repeat binding factor 4 (CmCBF4) could combine with the promoter of respiratory burst oxidase homologs D (CmRBOHD) to enhance the production of apoplastic H₂O₂. Further studies suggested that CmCBF4 could also activate the transcription of plasma membrane intrinsic protein 2;3 (CmPIP2;3), which has H₂O₂ transport capability in melon seedlings. In addition, abscisic acid-responsive element (ABRE)-binding factor 2 (CmABF2) and CmCBF4 could promote the transcription of each other to increase the expression of CmPIP2;3. Silencing CmCBF4 significantly reduced Tre-promoted cold tolerance and apoplastic H₂O₂ production and transport. In summary, this study reveals that CmCBF4 regulates Tre-promoted cold tolerance in melon seedlings by promoting the production and transport of apoplastic H₂O₂ signal.