Cloning and expression analysis of three members of PtYABBYs in Populus tomentosa

  Objective  YABBY is a unique transcription factor family in higher plants, which plays an important role in the development of lateral organs and flowering. In this study, we conducted cloning and bioinformatics analysis of PtYABBY genes, and explored the expression patterns of PtYABBY genes in eight stages of male and female flower buds and vegetative tissues such as roots, stems and leaves in order to lay a foundation for clarifying the function of PtYABBY genes on the development of lateral organs of Populus tomentosa.

  Method  The coding sequences of PtYABBY3, PtYABBY4 and PtYABBY11, homologous genes of FILAMENTOUS FLOWER (FIL) and YABBY3 (YAB3), were isolated from P. tomentosa by homologous gene cloning method, and bioinformatics analysis was performed. The expression patterns of three PtYABBYs in eight stages of male and female flower buds, roots, stems, young leaves and mature leaves were studied by qRT-PCR.

  Result  The lengths of PtYABBY3, PtYABBY4 and PtYABBY11 were 633, 642, 639 bp, encoding 210, 213, 212 amino acids, respectively. The proposed amino acid sequences all contained the C₂C₂ zinc finger domain and the YABBY domain. Phylogenetic analysis further indicated that three PtYABBYs belong to the FIL/YAB3 subfamily. qRT-PCR results showed that three PtYABBYs were expressed in roots, stems, leaves, male and female flower buds at eight stages. However, there were significant differences in the expression levels of PtYABBY genes. The expression level of PtYABBY3 was down-regulated at the early stage and up-regulated at the late stage of male and female flower bud development. From primordia formation to dormancy stage, the expression trends of PtYABBY3 in female and male flower buds were completely different. The expression levels of PtYABBY4 and PtYABBY11 were the highest during the floral induction stage, and decreased from floral induction stage to enlargement stage. During dormancy and microsporogenesis stage of male flower buds, there was no significant change in gene expression. The fluorescence quantitative results of vegetative tissues showed that the expression levels of three PtYABBYs were relatively high in young leaves and mature leaves, and the expression levels were the lowest in roots.

  Conclusion  PtYABBY3, PtYABBY4 and PtYABBY11, members of the YABBY gene family belong to FIL/YAB3 subclass. The expression levels of PtYABBYs are obviously different during 8 stages of female and male flower bud development in P. tomentosa, and relatively high in leaves and flower buds. The expressions of PtYABBY3, PtYABBY4 and PtYABBY11 may be related to the development of buds and leaves of P. tomentosa, which lays a foundation for further study of their roles in the development of poplar.