Blue Light Photoreception and Guard Cell Function

蓝光感光和保卫细胞功能

• 批准号: 9723605
• 负责人: Eduardo Zeiger
• 金额: $ 32.5万
• 依托单位: University of California-Los Angeles
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1997
• 资助国家: 美国
• 起止时间: 1997-09-01 至 2000-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9723605&HistoricalAwards=false
• 关键词: Blue; Light; Photoreception; Guard; Cell

9723605 Zeiger This research proposal focuses on blue light perception and transduction in guard cells, and its role in stomatal function. Guard cells sense internal and external signals in the leaf environment and integrate them into regulated stomatal apertures that control leaf gas exchange. The blue light response of guard cells belongs to a large family of blue light responses which are central to plant adaptations and acclimations to their environment. The identity of the chromophore(s) mediating blue light sensing in higher plants remains unknown. Recent work with hy4 and nph1, two Arabidopsis mutants for blue light- dependent inhibition of stem elongation and phototropism, has provided evidence for a flavoprotein mediating blue light photoreception. Both mutants however are reported to have normal stomatal responses to blue light, indicating that guard cells might have a distinct blue light photoreceptor. Recent studies have identified the carotenoid, zeaxanthin, as a putative blue light photoreceptor in guard cells. The blue light sensitivity of guard cells increases with their zeaxanthin content, and inhibition of zeaxanthin formation by dithiothreitol (DTT), inhibits blue light-dependent stomatal opening, without altering opening stimulated by guard cell photosynthesis.. In the proposed experiments, the blue light responses of guard cells from wild type Arabidopsis leaves will be characterized, and compared with that of the zeaxanthin-less mutant, npq1. This mutant has a defective violaxanthin de-epoxidase and is unable to accumulate zeaxanthin. Since the de-epoxidase gene appears to be a single copy gene, it is anticipated that npq1 guard cells will also lack zeaxanthin. We have recently confirmed that guard cells from npq1 are devoid of zeaxanthin. Gas exchange experiments with intact wild type and npq1 leaves will be used to establish whether Arabidopsis stomata have a typical response to blue light and whether the response has been altered by the lack of zeaxanthin in npq1. Guard cells in enzymatically cleaned epidermis will be used to study the stomatal response to blue light in isolated guard cells. Initial experiments have just shown that npq1 guard cells fail to open in response to blue light under a red light background. If detailed studies support this initial funding, the mutant will be used to test whether the inhibitor of zeaxanthin formation, DTT can mimic the genetic lesion in npq1. Other experiments will investigate a possible role of Ca2+ as a second messenger transducing blue light sensing at the guard cell chloroplast to a H+ ATPase at the guard cell plasma membrane. Patch clamp experiments in the whole cell configuration will be used to measure blue light-induced electrical currents at the guard cell plasma membrane, over a range of intracellular Ca2+ concentrations shown to alter proton pumping activity in guard cells. Isolated guard cell chloroplasts will be used to test whether blue light elicits Ca2+ fluxes across the chloroplast envelope that could account for in vivo changes in cytosolic Ca2+ concentrations. We will also investigate whether transgenic Arabidopsis plants expressing the Ca2+ indicator, aequorin, can be used to characterize Ca2+ fluxes between the chloroplast and the cytosol. The proposed research has significant potential for the conclusive identification of a blue light photoreceptor in guard cells and a mutant for stomatal responses to blue light, and for the detailed characterization of the sensory transducing cascade of an important blue light response. Plants perceive light in several wavelengths that control growth, orientation and development. Blue light perception and how it is signaled to mediate downstream effects has been a controversy. At the heart of the controversy is what pigment absorbs the perceived light and transmits the information downstream. Dr. Zeiger has obtained mutants of the pigment zeaxanthin synthesis and the mu tants exhibit effects that indicate that this pigment is responsible for perceiving blue light. With this award Dr. Zeiger will use mutant and wild type plants to analyze how zeaxanthin blue light photoreception signals opening response of guard cells mediating gas exchange in leaves. Other studies will focus on how zeaxanthin photoreception induces calcium fluxes in cells that mediate intracellular signaling. This research is important because it addresses one of the most basic aspects of how plants function by responding to light in its environment. ***

小行星9723605 这项研究计划的重点是保卫细胞的蓝光感知和转导，以及它在 气孔功能 保卫细胞感知叶片环境中的内部和外部信号， 它们进入控制叶片气体交换的调节气孔。 警卫的蓝光反应 细胞属于蓝光反应的大家族，其是植物适应的核心， 适应他们的环境。介导蓝光感测的发色团的身份在 更高的植物仍然未知。 最近的工作与hy4和nph 1，两个拟南芥突变体的蓝光依赖性抑制茎伸长和向光性，提供了证据，黄素蛋白 介导蓝光光感受。 然而，据报道，这两种突变体都具有正常的气孔 这表明保卫细胞可能具有独特的蓝光光感受器。 最近的研究已经确定类胡萝卜素，玉米黄质，作为一个假定的蓝光感光器在警卫， 细胞 保卫细胞的蓝光敏感性随玉米黄质含量的增加而增加， 二硫苏糖醇（DTT）的玉米黄质形成，抑制蓝光依赖的气孔开放， 改变保卫细胞光合作用刺激的开口。在实验中，蓝光 将表征来自野生型拟南芥叶的保卫细胞的响应，并与来自野生型拟南芥叶的保卫细胞的响应进行比较。 玉米黄质缺失突变体npq1的基因。 该突变体具有缺陷的紫黄质脱环氧化酶， 来积累玉米黄质。 由于脱环氧酶基因似乎是一个单拷贝基因， NPQ 1保卫细胞也缺乏玉米黄质。 我们最近证实，来自npq1的保卫细胞 不含玉米黄质将使用完整野生型和npq 1叶的气体交换实验， 确定拟南芥气孔是否对蓝光有典型的反应，以及这种反应是否具有 由于npq1中缺少玉米黄质而改变。 酶清洁的表皮中的保卫细胞将 用于研究离体保卫细胞对蓝光的气孔反应。 最初的实验 示出了NPQ 1保护单元在红光背景下响应蓝光不能打开。如果详细 研究支持这一初步资金，突变体将用于测试是否抑制玉米黄质 DTT可以模拟npq 1的遗传损伤。其他实验将研究一种可能的作用 Ca2+作为第二信使，将保卫细胞叶绿体的蓝光传感转换为H+， 保卫细胞质膜上的ATP酶。 膜片钳实验在整个细胞配置将 用于测量保卫细胞质膜上蓝光诱导的电流， 细胞内Ca2+浓度的变化改变了保卫细胞的质子泵活性。 隔离保护 细胞叶绿体将被用来测试蓝光是否激发Ca2+穿过叶绿体被膜 这可以解释体内细胞溶质Ca 2+浓度的变化。 我们亦会研究 表达Ca2+指示剂水母发光蛋白的转基因拟南芥植物是否可用于 叶绿体和胞质溶胶之间的Ca2+通量的特征。这项研究具有重大意义 潜在的决定性鉴定的蓝光感光细胞在保卫细胞和突变体， 气孔对蓝光的反应，以及感觉传导级联的详细表征 重要的蓝光反应。 植物感知几种波长的光，控制生长，定向和发育。蓝光 感知以及它如何被信号化以介导下游效应一直是一个争议。的核心 争论的焦点是什么色素能吸收感知到的光并将信息传递到下游。 Zeiger博士已经获得了色素玉米黄质合成的突变体，这些突变体表现出的效果是， 表明这种色素是感知蓝光的原因。Zeiger博士将利用这个奖项 突变体和野生型植物，以分析玉米黄质蓝光光感受信号如何开放响应 介导叶片气体交换的保卫细胞。其他研究将集中在玉米黄质如何 光感受诱导介导细胞内信号传导的细胞中的钙流。本研究是 重要的是，它解决了植物如何通过响应光来发挥作用的最基本方面之一 in its environment环境. ***