Genome-Wide Analysis of the UDP-Glycosyltransferase Family Reveals Its Roles in Coumarin Biosynthesis and Abiotic Stress in Melilotus albus

Coumarins, natural products abundant in Melilotus albus, confer features in response to abiotic stresses, and are mainly present as glycoconjugates. UGTs (UDP-glycosyltransferases) are responsible for glycosylation modification of coumarins. However, information regarding the relationship between coumarin biosynthesis and stress-responsive UGTs remains limited. Here, a total of 189 MaUGT genes were identified from the M. albus genome, which were distributed differentially among its eight chromosomes. According to the phylogenetic relationship, MaUGTs can be classified into 13 major groups. Sixteen MaUGT genes were differentially expressed between genotypes of Ma46 (low coumarin content) and Ma49 (high coumarin content), suggesting that these genes are likely involved in coumarin biosynthesis. About 73.55% and 66.67% of the MaUGT genes were differentially expressed under ABA or abiotic stress in the shoots and roots, respectively. Furthermore, the functions of MaUGT68 and MaUGT186, which were upregulated under stress and potentially involved in coumarin glycosylation, were characterized by heterologous expression in yeast and Escherichia coli. These results extend our knowledge of the UGT gene family along with MaUGT gene functions, and provide valuable findings for future studies on developmental regulation and comprehensive data on UGT genes in M. albus.     

Genome-Wide Identification of Maize Protein Arginine Methyltransferase Genes and Functional Analysis of ZmPRMT1 Reveal Essential Roles in Arabidopsis Flowering Regulation and Abiotic Stress Tolerance

Histone methylation, as one of the important epigenetic regulatory mechanisms, plays a significant role in growth and developmental processes and stress responses of plants, via altering the methylation status or ratio of arginine and lysine residues of histone tails, which can affect the regulation of gene expression. Protein arginine methyltransferases (PRMTs) have been revealed to be responsible for histone methylation of specific arginine residues in plants, which is important for maintaining pleiotropic development and adaptation to abiotic stresses in plants. Here, for the first time, a total of eight PRMT genes in maize have been identified and characterized in this study, named as ZmPRMT1-8. According to comparative analyses of phylogenetic relationship and structural characteristics among PRMT gene family members from several representative species, all maize 8 PRMT proteins were categorized into three distinct subfamilies. Further, schematic structure and chromosome location analyses displayed evolutionarily conserved structure features and an unevenly distribution on maize chromosomes of ZmPRMT genes, respectively. The expression patterns of ZmPRMT genes in different tissues and under various abiotic stresses (heat, drought, and salt) were determined. The expression patterns of ZmPRMT genes indicated that they play a role in regulating growth and development and responses to abiotic stress. Eventually, to verify the biological roles of ZmPRMT genes, the transgenic Arabidopsis plants overexpressing ZmPRMT1 gene was constructed as a typical representative. The results demonstrated that overexpression of ZmPRMT1 can promote earlier flowering time and confer enhanced heat tolerance in transgenic Arabidopsis. Taken together, our results are the first to report the roles of ZmPRMT1 gene in regulating flowering time and resisting heat stress response in plants and will provide a vital theoretical basis for further unraveling the functional roles and epigenetic regulatory mechanism of ZmPRMT genes in maize growth, development and responses to abiotic stresses.