Poster: Hormones

Abs # 621: Effect of brassinosteriods on auxin distribution through regulation of polar auxin transport

Presenter:	Xue, Hong-Wei , hwxue@sibs.ac.cn
Authors	Xue, Hong-Wei  (A)   Li, Li  (A)   Xu, Zhi-Hong  (A)
Affiliations:	(A): National Lab. of Plant Mol. Genet., Shanghai Inst. of Plant Physio. & Eco., The Chinese Academy of Sciences; and Partner Group of MPI of Mol. Plant Physio. (MPI-MP) on 揚lant Mol. Physio. & Signal Transduction?

It has been shown that plant cell elongation was stimulated by low concentrations of brassinosteroids (BRs) but inhibited under high concentration of exogenous BRs (more than 100nM) including the shorted seedlings, bending hypocotyls, inhibited growth of primary roots and more lateral roots; and auxin, involved in many parallel developmental processes as BR. Previous studies have evidenced the interactions between BRs and auxin (Clouse, 1998; Ephritikhine et al., 1999; Yin et al., 2002), while the polar auxin transport was indirectly involved, demonstrated by our studies. The present report indicated that BR could acceded the polar auxin transport, through regulating the expressions of genes encoding auxin efflux carriers (demonstrated by RT-PCR and Northern blotting analysis), and resulted in the alternation of the distribution of auxin from up to down, without changing the amounts in whole. BRs were able to stimulate the polar auxin transport via experiments employing ¹⁴C labeled IAA, accumulate endogenous auxin in the middle part of the primary root, and promote the lateral root development, as well as disperse in the cotyledons, which might relate to the negative tropism of seedlings. Our further studies on cell arrangement evidenced that BR positively regulated polar auxin transport and involved in a major role to recall cell responses in gravity perception and signal transport mechanisms. For correspondence: Hong-Wei Xue, hwxue@sibs.ac.cn