Evolutionary analysis of CBFs/DREB1s in temperate and tropical woody bamboos and functional study of PeDREB1A3 under cold and drought stress.

Bamboo forests are vulnerable to extreme cold, as well as drought caused by declining rainfall or persistent hot, under global climate change. The C-repeat binding factors/dehydration-responsive element binding protein 1s (CBFs/DREB1s) are vital to acquiring tolerance to deal with the changing climate in plants. Herein, we investigated the evolution of CBFs/DREB1s in four temperate or tropical woody bamboos. In Phyllostachys edulis, Hsuehochloa calcarea, Dendrocalamus latiflorus, and Dendrocalamus brandisii, a total of 16, 12, 24, and 22 putative DREB1s were identified and were categorized into nine subclades, from DREB1A to DREB1I. DREB1s members increased with bamboo polyploidization, coinciding with the presence of at least two collinear DREB1s orthologs in different bamboos. It indicates the importance of polyploidization in driving the expansion of DREB1s. Except for the DREB1F, DREB1s of the other subclades showed direct collinearity with their orthologs in Poaceae. Tandemly linked loci of DREB1A, DREB1H, and DREB1B were of concern due to their conserved and inherited relationship in bamboo, and a recent duplication of DREB1A occurred during bamboo speciation. In P. edulis, PeDREB1A3/PeDREB1H1/PeDREB1B3 locus showed sensitivity to cold stimulation, especially for PeDREB1A3 rapidly induced after 0.5-h cold stimulation. PeDREB1A3 was proved as a nuclear-located transcription activator recognizing DRE cis-element. Moreover, overexpression of PeDREB1A3 improved both cold and drought tolerance of Arabidopsis thaliana. It suggested that the neoteric duplication of DREB1As might contribute to bamboo adaptability. DREB1A represents the potential locus for improving agronomic traits in the future. This research provides valuable information for excavating potential genes for bamboo adaptation and will facilitate the research on bamboo breeding for stress tolerance.