Over-expression of chrysanthemum CmDREB6 enhanced tolerance of chrysanthemum to heat stress.

Background: Chrysanthemum is among the top ten traditional flowers in China, and one of the four major cut flowers in the world, but the growth of chrysanthemum is severely restricted by high temperatures which retard growth and cause defects in flowers. DREB (dehydration-responsive element-binding) transcription factors play important roles in the response to abiotic and biotic stresses. However, whether the DREB A-6 subgroup is involved in heat tolerance has not been reported conclusively.

Result: In the present study, CmDREB6 was cloned from chrysanthemum (Chrysanthemum morifolium) 'Jinba'. CmDREB6, containing a typical AP2/ERF domain, was classed into the DREB A-6 subgroup and shared highest homology with Cichorium intybus L. CiDREB6 (73%). CmDREB6 was expressed at its highest levels in the leaf. The CmDREB6 protein localized to the nucleus. Based on the yeast one hybrid assay, CmDREB6 showed transcription activation activity in yeast, and the transcriptional activation domain was located in the 3 'end ranging from 230 to 289 amino acids residues. CmDREB6 overexpression enhanced the tolerance of chrysanthemum to heat. The survival rate of two transgenic lines was as high as 85%, 50%, respectively, in contrast to 3.8% of wild-type (WT). Over-expression of CmDREB6 promoted the expression of CmHsfA4, CmHSP90, and the active oxygen scavenging genes CmSOD and CmCAT.

Conclusion: In this study, DREB A-6 subgroup gene CmDREB6 was cloned from chrysanthemum 'Jinba'. Overexpression of CmDREB6 enhanced heat tolerance of chrysanthemum by regulating genes involved in the heat shock response and ROS homeogenesis.