杨树YABBY转录因子家族的全基因组分析及PtoYABBY6 和PtoYABBY7 的功能研究

[Objective]To identify the poplar YABBY transcription factor family and reveal the functions of poplar YABBY transcription factor members PtoYABBY6 and PtoYABBY7 in the process of vegetative and reproductive growth,in order to lay a theoretical foundation for analyzing the molecular mechanism of YABBY transcription factors in regulating the flowering and lateral organ growth and development of poplar.[Method]A systematic genome-wide analysis of the poplar YABBY transcription factor family was carried out.Referring to the previous research of the group,the development of poplar flower buds was divided into eight periods:Period 1.flower induction;Period 2.floral primordium formation;Period 3.organogenesis;Period 4.elongation;Period 5.spore formation;Periods 6 and 7.dormancy;and Period 8.microsporogenesis.Mature leaves of Populus tomentosa,and roots,stems and leaves of Populus tomentosa aseptic group-cultivated seedlings were taken respectively,in addition,eight male and female flower buds at critical periods of development were taken at the periphery of the canopy as the tissue quantitative materials for the analysis of gene expression patterns.We also explored the expression pattern of YABBY gene in response to hormone and drought stress in combination with publicly available RNA-Seq data.On the basis of this analysis,we investigated the functions of PtoYABBY6 and PtoYABBY7,members of the"reproductive YABBY genes".[Result]A total of 13 YABBY genes,named PtrYABBY1-PtrYABBY13,were identified in poplar,and their coding sequences were distributed in the range of 498-657 in length.Except for PtrYABBY2,all PtrYABBY proteins have a complete C2C2 zinc finger structure at the N-terminal end,and all PtrYABBY proteins have a YABBY structural domain at the C-terminal end.All PtrYABBY proteins have a YABBY domain at the C-terminus.They were classified into five subfamilies by multi-species amino acid sequence comparison and phylogenetic analysis,and the members of these subfamilies have conserved gene structures and motifs.Promoter analysis revealed multiple cis-regulatory elements,and the results suggest that the YABBY gene may be involved in plant development and response to various phytohormones and abiotic stresses.Publicly available RNA-Seq data and expression analyzed by real-time quantitative PCR indicated that poplar YABBY genes have different expression patterns in organs and in response to hormones and drought stress.Subsequently,we functionally explored PtoYABBY6 and PtoYABBY7,which are significantly expressed during female bud development.Transgenic Arabidopsis overexpressing PtoYABBY6 had smaller leaf area during the nutrient growth stage and resulted in an early flowering phenotype during the reproductive growth stage.RT-qPCR results showed down-regulation of the expression of the cytokinin A-type response regulators ARR5,ARR6,and ARR7,down-regulation of the expression of the cell cycle genes CYCB1;1 and CYCD3;1,and up-regulation of the expression of TCP4,and up-regulation of the flowering-related genes related to flowering,FT expression was elevated,and FLC expression was decreased.The transgenic Arabidopsis leaves overexpressing PtoYABBY7 had altered abaxial polarity and resulted in a late-flowering phenotype.RT-qPCR results showed that the integrator of the flowering pathway FT was significantly down-regulated,and the expression of FIL and KAN genes,which were related to the distal polarity of leaves,were up-regulated,while the expression of REV and PHV genes,which were related to the proximal polarity of leaves,were down-regulated.[Conclusion]Members of the poplar YABBY transcription factor family were identified at the genome-wide level.The poplar PtoYABBY6 and PtoYABBY7 genes are involved in the processes of vegetative and reproductive growth,which are mainly manifested in the alteration of leaf development and flowering time,and the functions of the PtoYABBY6 and PtoYABBY7 genes were preliminarily revealed.