Identification And Functional Analysis Of CEP Peptide Gene Family In Rice(Oryza Sativa) And Maize(Zea Mays L.)

Plant peptide hormones, which usually contain less than 20 amino acids, play an important role in regulating plant developmental programs via cell-to-cell communication in a non-cell autonomous manner. At present, peptide hormones in plant mainly contain CLE family, RGF family, ERF family and CEP family. In this thesis, we performed a genome-wide survey of CEP genes in grain crop rice and maize using a bioinformatics approach. The functions of two genes (rice OsCEP6.1 and maize ZmCEP1) were characterized by ectopic transgenic strategy, with the purpose to futher providing the the reference basis of the relationship between CEPs and plant development, the details are as follows:1. Fifteen CEP genes were identified in rice genome based on peptides sequence conservation, which located on six out of ten rice chromosomes. Further analysis indicated that the CEP family could be divided into two groups according to phylogenetic tree analysis, and both of their C-terminal regions were highly conserved (SPGV/IGH).The in silico expression profiling revealed that OsCEP5 and OsCEP6.1 were specifically expressed in early inflorescences and emerging inflorescences.2. OsCEP6.1 showed a spatial-temporal expression pattern in different tissues of rice using qRT-PCR. In addition, the expression level of OsCEP6.1 was also significantly up-regulated by exogenous cytokinin. Application of a chemically synthesized 15-amino acid OsCEP6.1 peptide showed that OsCEP6.1 had a negative role in regulating root and seedling growth. Moreover we ectopically expressed OsCEP6.1gene in rice, and the overexpression of OsCEP’6.1 resulted in shorter plant height, fewer tillers and smaller flag leaves in rice. Furthermore, the panicle lengths, the number of primary and secondary rachis branches, grain number per panicle, grain length, grain width and 1,000 grain weight were also negatively affected in the transgenic lines compared with the control. Scanning electron microscopy analysis revealed that the phenotypic variation of OsCEP6.1 overexpression lines resulted from decreased cell size but not reduced cell number.3. Twelve CEPs were identified in maize genome by a bioinformatics approach based on peptides sequence conservation, which located on eight out of ten maize chromosomes. Further analysis indicated that the CEP family in maize also could be divided into two groups according to Phylogenetic tree constructed on the basis of CEP domain sequences. The in silico data indicated that ZmCEPl had a high expression in maize developmental ears and tassels.4. To explore the biological functions of ZmCEPl in maize, expression patterns analysis found that ZmCEPl had a high expression in developmental ears and tassels, and could respond to 6-BA, In situ hybridization revealed that ZmCEPl was expressed in vascular tissues of ear cob and ear developmental florets. Overexpression of ZmCEPl in Arabidopsis contributed to depressed primary root and plant height. The overexpression of ZmCEPl in maize resulted in shorter plant height and shorter ear height. Moreover, ear lengths, ear diameters, kernel lengths and hundred kernel weights also were significantly reduced in the transgenic lines compared with control, while ear row number showed no significant changes.