Study On The Function Of Arabidopsis Thaliana LBD Gene Family In Root - Regeneration

Attempted to resist adversity, plant have evolved a variety of mechanisms, including regeneration as one of the most significant. The processes of plant regeneration allow for the healing of wounded tissues,the formation of new organs from detached explants, or the differentiation of somatic cells back into embryo-stage. The capacity of asexual reproduction, i.e. to produce the next generation with out seeds, is determined by the regenerative capacity of a certain species in most cases. Tissue culture, grafting, cutting and etc. are widely used in agriculture for various purposes including the selective breeding of plants without desirable traits, or production of multiple organisms in the absence of seeds or appropriate pollinators. Therefore, research on plant regeneration is remarkably significant for agriculture, forest and plant preservation. Despite of wide spread of utilization, the molecular bases behind many aspects of plant regeneration remain unclear. In order to uncover the mechanisms, our lab has groped for a system that adventitious roots come out from detached rosette leaves of Arabidopsis thaliana on B5medium. Excluding external interference from phytohormone is one of its advantages. Attempted to elucidate the molecular mechanisms underlying de novo root regeneration, cell morphological observation, molecular genetic detection and biochemical level identification are all involved. During the process of the detached leave regenerating an adventitious root, procambium cells and their surrounding parenchymal cells shift into root founder cells marked by WUSCHEL RELATED HOMEOBOX11(W0X11) after the first step of cell fate transition, and finally become root primordium cells within the second step of cell fate transition. The article is based on the data of microarray during callus formation from Dr. Shujing Liu and implied by the previous report that LATERAL ORGAN BOUNDARIES DOMAIN (LBD) gene family are involved in lateral root formation. Firstly, the expression of LBD16/18/29/33-members of the LBD gene family that high-level homologous and all participate in the process of lateral root formation-were detected, which demonstrate that the expression of LBD16and LBD29are dramatically unregulated from none in the start to a high level in the end. Because of apparent ectopic expression of LBD29in35Spro:WOX11transgenic plant, it was selected as the research focus. The explants of LBD29overexpression lines formed more adventitious root than did the wild type or even formed callus spontaneously. pER8:LBD29-SRDXtransgenic plants were constructed and showed reduced ability to form roots. These phenotypes are similar to those observed in the corresponding analyses for WOX11. In addition, overexpression of LBD29in the35Spro; WOX11-SRDX background was able to partly rescue the regeneration defect caused by loss of WOX functions. In contrast, upregulation of WOX11expression was not detected in leaves of the35Spro:LBD29transgenic plants. The in vitro interaction of WOX11and the promoter of LBD29was confirmed by EMS A. Taken together, these results indicate that LBD29,the key factor influence the second step of cell fate transition, acts downstream of WOX11, and WOX11regulates adventitious root formation at least partly through the LBD pathway. It is the first time that LBD29was found the key transcription factor regulating the second step of cell fate transition during de novo rooting and its regulatory relationship with WOX11was elucidated. Moreover, LBD gene family might be a hub between the initiation of lateral roots and adventitious roots.