专业英语PPT-生长素运输.pptx

Auxin Transport, but in Which Direction?; The plant hormone auxin has remarkably diverse roles in the regulation of growth and development. Auxin, synthesized in shoot apices, is moved along specific transport routes through the plant by unique polar transport machinery. Polar auxin flow is primarily dependent on polar efflux from cells, with the resultant directed transport providing a constant stream of information. ; Auxin flow can be influenced by both exogenous and endogenous stimuli, triggering (启动；触发）redistribution of auxin and specific growth and developmental responses. This intercellular communication system is conceptually similar to the animal nervous system, and its transmission rate of 1 cm/hour is fast enough for systemic signaling in a sessile（固定的） organism.; Over the past decade, several classes of integral（完整的；必需的） membrane proteins have been implicated in auxin flow. Mutations in these protein families perturb auxin distribution, causing diverse phenotypes, but their interrelationships and the biochemical basis for their action have remained obscure. Petrá?ek et al. provide long-awaited evidence that PIN-FORMED (PIN) proteins act directly in transporting auxin out of cells, substantially（基本上） independently of the PGP family of auxin pumps. Moreover, Wi?niewska et al. report that polar PIN localization in cells is a primary determinant（决定因素 ）of the direction of auxin efflux. And, coming in from the opposite direction, a third report by Dharmasiri et al. identifies a candidate regulator for the localization of AUX1, a protein that mediates cellular influx of auxin.; The PIN-FORMED family was so named because mutations in one family member, PIN1, result in failed lateral（侧面的） organ formation at the shoot apex of Arabidopsis thaliana, causing a pinlike shoot. PIN proteins are polarly localized in cells in positions correlating with auxin flow, and PIN-like phenotypes result from treatment with inhibitors of polar auxin transp