Novel function of a putative TaCOBL ortholog associated with cold response.

The plant COBRA protein family plays an important role in secondary cell wall biosynthesis and the orientation of cell expansion. The COBRA gene family has been well studied in Arabidopsis thaliana, maize, rice, etc., but no systematic studies were conducted in wheat. In this study, the full-length sequence of TaCOBLs was obtained by homology cloning from wheat, and a conserved motif analysis confirmed that TaCOBLs belonged to the COBRA protein family. qRT-PCR results showed that the TaCOBL transcripts were induced by abiotic stresses, including cold, drought, salinity, and abscisic acid (ABA). Two haplotypes of TaCOBL-5B (Hap5B-a and Hap5B-b), harboring one indel (----/TATA) in the 5' flanking region (- 550 bp), were found on chromosome 5BS. A co-dominant marker, Ta5BF/Ta5BR, was developed based on the polymorphism of the two TaCOBL-5B haplotypes. Significant correlations between the two TaCOBL-5B haplotypes and cold resistance were observed under four environmental conditions. Hap5B-a, a favored haplotype acquired during wheat polyploidization, may positively contribute to enhanced cold resistance in wheat. Based on the promoter activity analysis, the Hap5B-a promoter containing a TATA-box was more active than that of Hap5B-b without the TATA-box under low temperature. Our study provides valuable information indicating that the TaCOBL genes are associated with cold response in wheat.