Abstract:

Objectve: Lots of studies have shown that there are differences in the distribution of cytokinins in Phyllostachys edulis different internodes which are growing fast, which may be one of the main causes of rapid growth of P. edulis. So the study was intended to explore the effect of expression patterns of cytokinin-related key genes in the rapid growth of P. edulis shoot, and provide a theoretical basis for further elucidation of the rapid growth mechanism. Method: We extracted cytokinin-related gene families by the retrieval of Arabidopsis thaliana genome database, Oryza sativa genome database and KEGG metabolic pathway. The cytokinin-related key genes were identified by NCBI, Pfam and SMART online. The P. edulis genome database was blasted with the obtained cytokinin-related key gene family to extract P. edulis related key genes. The evolutionary relationships of homologous proteins were analyzed by constructing phylogenetic trees and motifs of homologous proteins. The expression patterns of cytokinin-related gene and their effects on the rapid growth of P. edulis were investigated by qRT-PCR with different internode tissues of rapidly growing P. edulis. Result: There are five cytokinin-related key gene families including isopentenyl-transferases family, cytokinin oxidase family, histidine kinases family, histidine phosphotransferase family and response regulator family. The cytokinin-related key genes of P. edulis is more closely phylogenetic to rice genes. The motifs of gene families in Arabidopsis, rice, and P. edulis are highly conserved, but some homologous genes show species-specific. The expression of five key gene families were specifically analyzed by qRT-PCR. The results showed that the expression level of the PhIPT2 was higher in young internodes and the PhIPT1 decreased slightly; while the expression level of PhCKXs decreased gradually; the expression level of receptor gene PhHKs was not stable in different internodes of P. edulis; the expression level of the transporter PhHPs increased slightly with the younger internodes; the expression level of the response regulator PhRRs increased and decreased between different internodes. Conclusion: The most cytokinin-related key genes are highly conserved in structure and biological function, but some of them are species-specific in structure and evolution. The expression patterns of cytokinin-related key genes in P. edulis shoot were studied, and the content of cytokinin in the morphologically upper part of P. edulis was higher than that in morphologically lower part. Therefore, we supposed that cytokinin plays a major biological function in the rapid growth of P. edulis, and regulates the growth and thickening of stems.

Key words: Phyllostachys edulis, cytokinin, rapid growth, evolutionary system, expression pattern