Genome-wide characterization of the NUCLEAR FACTOR-Y (NF-Y) family in Citrus grandis identified CgNF-YB9 involved in the fructose and glucose accumulation

摘要

Background Nuclear factor Y (NF-Y) is increasingly known to be involved in many aspects of plant growth and development. To date, the systematic characterization of NF-Y family has never been reported in Citrus grandis. Objective Genome-wide characterization of C. grandis NF-Y (CgNF-Y) family and analysis of their role in sucrose metabolism. Methods NF-Y conserved models were employed to identify CgNF-Y genes from genomic data. Phylogenetic tree was generated by the neighbor-joining method using program MEGA 7.0. Based on our previous transcriptomic data, the transcription levels were calculated by RSEM software and were clustered by ShortTime-series Expression Miner. The plant expression vector of CgNF-YB9 was constructed using In-Fusion Cloning and transferred into tobacco by leaf disc transformation method. Soluble sugars and gene expressions were analysis by HPLC and qRT-PCR, respectively. Results A total of 24 CgNF-Y genes (6 CgNF-YAs, 13 CgNF-YBs and 5 CgNF-YCs) were identified with conserved domains. Phylogenetic analysis of the NF-Y proteins indicated that NF-YA, NF-YB and NF-YC could be categorized into four, five and three clades, respectively. Expression profiling analysis reflected spatio-temporally distinct expression patterns for CgNF-Y genes. Importantly, we observed a positive correlation between the expression level of CgNF-YB9 and the content of soluble sugar. Moreover, CgNF-YB9-corelated genes were enriched in carbohydrate metabolism. In CgNF-YB9 overexpression lines, sucrose content showed a decrease, whereas glucose and fructose contents displayed an increase. As expected, the transcription levels of sucrose-phosphate synthase and vacuolar invertase in transgenic Line 3 were observed with significantly down- and up-regulated, respectively. Conclusions The structure, phylogenetic relationship and expression pattern of 24 CgNF-Y genes were identified, and CgNF-YB9 was involved in sucrose metabolism.