NASA/NSF Collaborative Research: Blue-Light Signal Transduction in Arabidopsis Seedlings: A Multidisciplinary Study

MCB 9416016斯波尔丁 蓝光诱导一个大的，短暂的膜去极化前几秒钟的一个大的减少在黄化苗茎伸长的速度。 介导这种去极化的分子机制尚不清楚，尽管有证据表明质膜H+-ATP酶被抑制，阴离子通道被激活。 拟议的工作是一个电生理调查的离子转运的变化，在质膜参与转导蓝光到生长抑制。 将用膜片钳技术研究黄化的拟南芥下胚轴的生长细胞，以表征在蓝光脉冲后经历活性变化的离子通道。 将特别关注阴离子选择性通道的参与。 蓝光对H+-ATP酶活性的影响将通过电生理学和生物化学来确定。 除了野生型之外，还将研究拟南芥中不显示蓝光抑制生长的突变体。 明确定义的蓝光能量和波长将用于构建不同基因型的电响应的幅度和动力学的注量率响应曲线。 将构建至少一个双突变体blu 1 hy 4，并进行类似的研究。 结果将证明遗传病变是否以及如何影响这些早期蓝光诱导的膜转运变化。 这种电生理学、生物化学和遗传学的结合有望揭示将蓝光受体与生长控制机制联系起来的转导链的一些重要特征。 %在黑暗中生长的幼苗在光照下经历一系列发育变化，从而产生能够进行光合作用的绿色植物。 这一重要发育过程的一个方面是明亮的蓝光对茎伸长的抑制。 几秒钟后，蓝光脉冲抑制了茎的生长。 这意味着吸收蓝光的受体与控制茎生长速度的机制密切相关。 在蓝光受体激活和生长反应开始之间发生的事件被认为是将蓝光转化为生长抑制。 这些事件统称为转导链。 目前对这条转导链的了解是，在细胞生长速度减慢之前，离子穿过细胞外膜的运输发生了变化。 拟议的工作重点是在分子水平上阐明蓝光如何改变膜中离子泵和通道的活性以及这如何影响幼苗生长速率的细节。 膜片钳的电生理技术将用于许多实验，所有这些实验都将在拟南芥植物上进行 此外，利用拟南芥中不显示蓝光抑制生长的突变体的存在的遗传技术将被起诉，一些生物化学技术也将被起诉。 总之，这些实验将揭示光如何控制植物生长和发育以及离子通道和泵如何参与环境信号转导的某些方面。 ***

MCB 9416016 Spalding Blue light induces a large, transient membrane depolarization a few seconds before a large reduction in the rate of stem elongation in etiolated seedlings. The molecular mechanism that mediates this depolarization is unknown although there is evidence that the plasma membrane H+-ATPase is inhibited and anion channels are activated. The proposed work is an electrophysiological investigation of the changes in ion transport at the plasma membrane that participate in the transduction of blue light into growth inhibition. The growing cells of etiolated Arabidopsis hypocotyls will be studied with the patch clamp technique to characterize the ion channels that undergo a change in activity after a pulse of blue light. The participation of anion-selective channels will be given particular attention. The effect of blue light on the activity of the H+-ATPase will be determined both electrophysiologically and biochemically. Mutants in Arabidopsis that do not display blue-light inhibited growth will be studied in addition to the wild-type. Well defined energies and wavelengths of blue light will be used to construct fluence rate response curves for the magnitudes and kinetics of the electrical responses of the different genotypes. At least one double mutant, blu1 hy4, will be constructed and similarly studied. The results will demonstrate if and how the genetic lesions affect these early blue-light induced changes in membrane transport. This combination of electrophysiology, biochemistry and genetics is expected to reveal some important features of a transduction chain that links blue- light receptors to a growth control mechanism. %%% Seedlings grown in the dark undergo a suite of developmental changes upon illumination, resulting in a green plant that is competent to perform photosynthesis. One aspects of this important developmental process is the inhibition of stem elongation by bright blue light . A pulse of blue light inhibits stem growth after a few seconds. This means a receptor that absorbs blue light is closely connected to a mechanism that controls the growth rate of the stem. The events that occur between the activation of the blue light receptor and the beginning of the growth response are said to transduce the blue light into growth inhibition. Collectively these events are called a transduction chain. All that is currently known about this transduction chain is that the transport across the cells outer membrane of ions is altered just before the growth rate slows. The proposed work is focused on elucidating at the molecular level the details of how blue light alters the activities of ion pumps and channels in the membrane and how this then affects the seedlings growth rate . The electrophysiological technique of patch clamping will be used for many of the experiments, all of which will be performed on the Arabidopsis plant In addition, genetic techniques to take advantage of the existence of mutants in Arabidopsis which do not display blue light inhibited growth will be sued, as will some biochemical techniques. Taken together, these experiments will reveal certain aspects of how light controls plant growth and development and how ion channels and pumps participate in the transduction of environmental signals. ***