摘要14-李承

An in vitro system for xylem cell differentiation in ArabidopsisCheng Li (李承, 14级)* (College of Life Sciences, Peking University, China), Xinqiang He (贺新强) (College of Life Sciences, Peking University, China)During vascular development, some procambial and cambial cells can self-proliferate and others will differentiate into xylem or phloem cells.The two processes are regulated by a signalling pathway which comprises a peptide ligand and its receptor and they are tracheary element differentiation inhibitory factor (TDIF) and TDIF RECEPTOR(TDR).Some papers have shown that glycogen synthase kinase 3 proteins (GSK3s), which are crucial downstream complements of this signalling pathway, can curb the process of xylem cell differentiation from procambial or cambial cells.It is very hard to investigate the tracheary element differentiation from procambial or cambial cells in vivo, because the vascular tissue is always deeply embedded. So we improved an in vitro experimental system with Arabidopsis thaliana cotyledon cultures using bikinin, a specific inhibitor of GSK3s. Compared with other in vitro systems of xylem cell differentiation, this system is fast, convenient and has a more obvious result. Expression analysis of the specific marker genes during the culture have revealed that mesophyll cells in cotyledons dedifferentiate into procambial cells, and then differentiate into tracheary elements.Using this system, we have found several E3 ligases of 26S proteasome/ubiquitin pathways may be indispensable for xylem cell differentiation, for example ATL11 and ATL8, the expression level of them are up-regulated in the process. More experiments, including phenotype analysis of the mutants and overexpress lines, are undergoing to get more data.In a word, the cotyledon culture system can be a useful tool to investigate xylem cell differentiation of Arabidopsis thaliana. It would be in