Abstract: [Objective] WOX transcription factor family is one of the plant-specific transcription factor families, which have been demonstrated playing an important role in the embryonic patterning, stem cell maintenance and proliferation and lateral organ development. This study analyzed the roles of PtoWOX11/12a gene from Populus tomentosa in the development of leaves and stems of transgenic 84K poplar(Populus alba×P. glandulosa cl. 84K). The gene expression level during the process of adventitious roots formation of Populus tomentosa,and in overexpression and suppressed expression of PtoWOX11/12a transgenic 84K poplars were analyzed. Our research provides a foundation for further studies of the roles of WOXs gene in plant development.[Method] The leaf shape, height and basal diameter of one-month-old to three-month-old transgenic lines and non-transgenic 84K poplar (control) in the greenhouse were measured and compared. The anatomy of stem sections of the 5^th, 9^th and 13^th internodes of transgenic lines and control plants was analyzed and the width of xylem and cambium were compared. The expression of PtoWOX11/12a, YUCCA1 and YUCCA8 during the process of adventitious roots development in P.tomentosa and in overexpression and suppressed expression of PtoWOX11/12a transgenic 84K poplars was examined using quantitative real-time PCR (qPCR).[Result] There were no significant differences between overexpression of PtoWOX11/12a and control plants in leaf length, but the leaf width of overexpression of PtoWOX11/12a was sharply larger than the control. The leaf length and width of suppression expression PtoWOX11/12a transgenic poplars were less than control, and the leaf margin had serrate incision. The height and diameter of overexpression and suppression expression PtoWOX11/12a transgenic poplars were significantly less than the control poplars. The anatomy analysis indicated that the xylem, the number of cambium layers of overexpression PtoWOX11/12a transgenic poplars was thinner than the control and the xylem of the suppression expression of PtoWOX11/12a was also thinner than the control, but it is wider than overexpression PtoWOX11/12a transgenic poplars. qPCR analysis showed that PtoWOX11/12a was strongly induced and expressed in the stem during the process of adventitious roots development. The expression levels of auxin synthesis genes, YUCCA1 and YUCCA8, were increased at the third day. Furthermore, their expression levels were increased in overexpressed while decreased in suppressed PtoWOX11/12a transgenic poplars.[Conclusion] Overexpression or suppression expression of PtoWOX11/12a gene has effects on plant leaf shape, height and stem radial growth (secondary xylem development). PtoWOX11/12a gene participates in adventitious roots formation and elongation involved in the expression of auxin synthesis genes YUCCA1 and YUCCA8. In the process of root formation, expression time interval was existed among PtoWOX11/12a, YUCCA1 and YUCCA8 genes. Higher expression of PtoWOX11/12a may inhibits the expression of auxin synthesis genes, thus overexpression PtoWOX11/12a transgenic poplars are easier to form meristem, promote root primordium formation and produce large number of adventitious roots. During adventitious root growth, the increased expression level of YUCCA1 and YUCCA8 promote auxin synthesis and root meristem cell division. In stem the increased activities of cambium affected the xylem differentiation in overexpression PtoWOX11/12a transgenic poplars, thus the xylem of transgenic poplars is thinner in size than the control.

Key words: Populus, PtoWOX11/12a, gene expression, quantitative real-time PCR, adventitious root, cambium