Genome-wide comparison of the GRAS protein family in eight Rosaceae species and GRAS gene expression analysis in Chinese white pear (Pyrus bretschneideri Rehder)

The GRAS protein family encodes a family of plant-specific transcription factors that have diverse and significant functions in regulating plant development and anthocyanin biosynthesis. Our study represents the comprehensive identification and comparison of GRAS protein family genes in the Rosaceae. Here, 535 GRAS genes were screened from eight Rosaceae species. Phylogenetic analysis revealed that whole-genome duplication (WGD) events and dispersed duplication events were the major mechanisms promoting the expansion of the GRAS protein family in these Rosaceae species. Furthermore, selection pressure caused by different duplication events indicates that GRAS genes were mainly under purifying selection during the evolution process, suggesting that strong functional restriction affected the evolution of GRAS genes. Analysis of gene expression patterns and qRT-PCR assays showed that GRAS genes were widely participating in the development of pear and that expression could be tissue-specific. In particular, further analysis indicated that Pbr010864.1 and Pbr024549.1 might be two important candidate genes during anthocyanin biosynthesis in pear. Our study is the first to perform a comprehensive analysis of the GRAS genes in pear and other Rosaceae species. These results presented here provide profitable information for understanding the process of the GRAS genes evolution and the possible improvement of pear fruit quality.