Genome-wide identification and expression analysis of glycine-rich protein genes in Chinese cabbage (Brassica rapa L. ssp. pekinensis)

Abstract

Background Plant Glycine-rich proteins, a superfamily with a glycine-rich domain, play an important role in various stress such as low temperature, drought, high salt, and so on. Although the research of GRP genes has been reported in many plants, the GRP gene has seldom reported in Chinese cabbage so far. Research results made a guide to further understand the function of BrGRP genes in Chinese cabbage. Results In this study, a total of 141 glycine-rich protein genes were identified in Chinese cabbage by homology comparative analysis. A further prediction of physical and chemical characteristics revealed that 58.3% of BrGRPs were alkalines, 63.1% of BrGRPs were unstable, and 73.8% were hydrophilic. Conserved domain analysis showed that 110 BrGRPs contained 18 same conserved motifs, and could be classified into five main subclasses which the evolutionary relationship and gene structure may be conserved while the other 31 BrGRPs, including Bra014168 , Bra040002 , etc, may gain new functions or gradually lost gene functions according to the evolution process. These identified BrGRP genes were also located in ten chromosomes and three different subgenomes of Chinese cabbage, and 101 pairs of orthologous GRP genes were found between Chinese cabbage and Arabidopsis. According to the opened transcriptome data, we found that 138 BrGRP genes showed abnormal expression at high temperature, 108 BrGRP genes showed abnormal expression at low temperature, and 74 at drought stress, 47 at soft rot stress, while only 3 and 7 genes at ozone and salt stress, respectively. Further promoter motif analysis found that a large number of stress-related cis-acting elements, such as DRE, MYC, MYB, and ABRE, were identified in their promoter regions, which were in correspondence with previous differential expression. In addition, some BrGRP genes were involved in multiple stresses suggested their broad-spectrum resistance. Conclusion A total of 141 GRP genes were identified in Chinese cabbage, which suggested their potential roles in plant stress response. But the molecular mechanisms by which BrGRP genes respond and resist biotic and abiotic stress remain unclear. These results may provide an important basis for the study of their function in Chinese cabbage.