As a serious environmental stress, low temperature (cold stress) disrupts cellular homeostasis and limits plant growth. In order to respond to seasonal changes in temperature, the immotile plants have developed complex biochemical and physiological processes. In these process, a number of plant hormones and genes, and several transcription factors in particular play pivotal roles in plant cold stress response.  

Several eukaryotic Heme-associated proteins (HAPs) have been reported to bind specifically to DNA fragments containing CCAAT-box; however, the physiological functions and direct targets of these HAP proteins in plants remain unclear.  

Dr. SHI Haitao from the research group led by Prof. CHAN Zhulong at Wuhan Botanical Garden investigated the in vivo role of AtHAP in plant cold stress by modulating expression of AtHAP5A (At3g48590).  

Results demonstrated that AtHAP5A as a transcription factor interacted with CCAAT motif in vivo, and AtXTH21, one direct target of AtHAP5A, was involved in freezing stress resistance. The AtHAP5A overexpressing plants were more tolerant, whereas the loss-off-unction mutant of AtHAP5A was more sensitive to freezing stress than wild-type plants. Chromatin immunoprecipitation (ChIP) assay showed that AtHAP5A could bind to five fragments that contained CCAAT motifs in the AtXTH21 promoter. Phenotype and genetic evidences revealed that AtHAP5A modulates freezing stress resistance through interaction with the CCAAT motif of AtXTH21 in Arabidopsis. 

This research entitled “AtHAP5A modulates freezing stress resistance in Arabidopsis through binding to CCAAT motif ofAtXTH21” was published in New Phytologist (doi: 10.1111/nph.12812, 5-year IF=6.888) online. 

Transactional activation activity and subcellular localization of AtHAP5A. (a) Transactivation activity of AtHAP5A in yeast. (b) Nuclear localization of AtHAP5A in 7-d-old Arabidopsis seedling root elongation regions and root tips of 35S::GFP-AtHAP5A transgenic plant. (Image by WBG)