Isolation and characterization of ERECTA genes and their expression patterns in common wheat (Triticum aestivum L.)

The orthologue of Arabidopsis ERECTA gene (ER) in wheat, TaER, is considered to be a promising candidate gene for the genetic improvement of water use efficiency (WUE) and drought tolerance in breeding programs. In this study, we isolated two distinct homologues (TaER1 and TaER2) of TaER genes in common wheat through in silico screening and PCR-based homologous cloning. Sequence analysis revealed that these two genes had a similar intron/exon structure with 27 exons and 26 introns, and each of them encode a putative Leucine-rich repeat receptor-like serine/threonine protein kinase in common wheat. The coding sequence (CDS) is 2928 bp for TaER1, encoding a protein with 975 amino acid residues, and 2931 bp for TaER2 deduced to encode 976 amino acid residues, and their corresponding genomic DNA sequences are 6858 bp and 7114 bp, respectively. Cloning and sequencing of 55 TaER cDNA clones revealed five transcript variants of TaER1 and nine spliced isoforms of TaER2, designated as TaER1.1 to TaER1.5 and TaER2.1 to TaER2.9 respectively. Genome specific primers were designed based on the sequence divergence of the promoter regions between the two homologous genes. PCR amplification from genomic DNA of Chinese Spring (CS) nullisomic-tetrasomic lines revealed that TaER1 and TaER2 were located on chromosomes 7D and 7B in common wheat, respectively. TaER1 and TaER2 have therefore been renamed as TaER-D1 (GeneBank accession: JQ599260.2) and TaER-B1 (GeneBank accession: JQ599261.2) respectively. Real-time quantitative RT-PCR analysis showed that the TaER genes were strongly expressed in young immature tissues and organs and could be up-regulated by numerous environmental stresses, such as drought, salinity, cold stress and heat stress. This indicated that it may play significant roles in wheat growth and development and be a regulator in the response to environmental stress.