Environmental modulation of Arabidopsis light foraging strategies

拟南芥光觅食策略的环境调节

• 批准号: NE/F004869/1
• 负责人: Keara Franklin
• 金额: $ 33.61万
• 依托单位: University of Leicester
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2008
• 资助国家: 英国
• 起止时间: 2008 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FF004869%2F1
• 关键词: Environmental; modulation; Arabidopsis; light; foraging

As ectothermic, sessile organisms that cannot choose their surroundings, plants must adapt their growth and development to the prevailing environmental conditions. Plants monitor their surroundings by integrating multiple stimuli, of which light and temperature signals are the most important. Light signals are perceived using a family of photoreceptors named phytochromes. Upon absorption of red wavelengths, phytochromes are converted to their active form which inhibits stem elongation and promotes leaf development. Absorption of far-red wavelengths, however, converts phytochromes back to their inactive form. When growing in crowded communities, plants compete with neighbouring vegetation for light to fuel photosynthesis. The presence of neighbouring vegetation is detected as a reduction in the ratio of red to far red wavelengths (low R:FR ratio) in the light reflected from or transmitted through green tissues. This change in light quality results in a reduction in active phytochrome in shaded plants and initiates a suite of elongation responses termed the shade avoidance syndrome, often at the expense of leaf development. These responses serve to elevate leaves towards gaps in the canopy and can be studied in the laboratory by growing plants in white light supplemented with far-red wavelengths. The majority of published experiments use growth temperatures in excess of 20oC to study shade avoidance responses. When grown at cooler temperatures, however, the leaf expansion response of Arabidopsis to low R:FR ratio is strikingly reversed. Plants grown in low R:FR ratio at 16oC display significantly increased leaf area, thickness and plant biomass when compared to high R:FR ratio-grown controls. Our observations suggest that Arabidopsis displays plasticity in light foraging strategy with the precedence of each strategy being determined by ambient growth temperature. At temperatures >20oC, Arabidopsis plants forage for light by raising and elongating leaves/petioles towards gaps in the canopy (shade avoidance syndrome 1, SAS1). At cooler temperatures, however, an alternative strategy is adopted, whereby plants dramatically expand leaf area and thickness, which is likely to increase photon capture (SAS2). In this proposal we aim to perform detailed analyses of leaf anatomy and photosynthetic performance in plants grown in high and low R:FR ratio across a broad spectrum of growth temperatures. We propose to investigate the possibility that different shade avoidance strategies are seasonal through experiments in unheated glasshouses in multiple seasons. The adaptive value of plasticity in shade avoidance strategy will be investigated through competition and fitness experiments using mutants and accessions displaying only SAS1. Natural genetic variation in shade avoidance strategy will be exploited using QTL mapping to identify regions of the genome responsible for such variation. This will ultimately enable the identification of key genes involved in this process. In addition, we have observed co-incidence of SAS2 and expression of the CBF regulon, a suite of genes involved in cold acclimation and acquisition of freezing tolerance. We therefore propose to map QTLs associated with low R:FR ratio-mediated induction of the CBF regulon and compare with QTLs identified for SAS2.

作为无法选择周围环境的饮热生物，植物必须使其生长和发育适应现行的环境条件。植物通过整合多种刺激来监测周围环境，其中最重要的是光和温度信号。使用一个名为植物色素的感光体系列来感知光信号。吸收红色波长后，将植物色素转化为其活性形式，从而抑制茎伸长并促进叶片发育。然而，远红色波长的吸收将植物色素转化回它们的非活性形式。在拥挤的社区中生长时，植物与邻近植被竞争，以供光合作用。检测到相邻植被的存在是在反射或通过绿色组织传播的光中红色与远红色波长（低r：fr比率）的降低。光质量的这种变化导致阴影植物中活性植物色素的降低，并引发了一套伸长反应，称为避免阴影综合征，通常以叶片发育为代价。这些反应可将叶子升高到树冠中的间隙，并可以通过在补充远红色波长的白光下种植植物在实验室中进行研究。大多数已发表的实验都使用超过20oC的生长温度来研究避免阴影的反应。然而，当在较冷的温度下生长时，拟南芥对低r：fr比率的叶片扩展响应显着逆转。与高R：FR比率增长的对照相比，在16oC时以低R：FR比率生长的植物显示出明显增加的叶面积，厚度和植物生物量。我们的观察结果表明，拟南芥在光觅食策略中显示可塑性，每种策略的优先级由环境生长温度决定。在温度> 20oC时，拟南芥植物通过抬高和拉长叶子/叶柄向冠层的间隙（SAS1，SAS1）提高叶子/叶柄来觅食。然而，在较冷的温度下，采用了另一种策略，从而大大扩大叶片面积和厚度，这可能会增加光子捕获（SAS2）。在此提案中，我们旨在对在广泛的生长温度中以高和低R：FR比率生长的植物的叶片解剖结构和光合作用性能进行详细分析。我们建议调查通过多个季节中未加热的温室中的实验进行季节性的不同阴影避免策略的可能性。在避免阴影中，可塑性的适应性值将通过使用仅显示SAS1的突变体和加入的竞争和健身实验来研究。将使用QTL映射来利用阴影回避策略中的自然遗传变异，以识别负责这种变异的基因组的区域。这最终将使该过程中涉及的关键基因的识别。此外，我们已经观察到SAS2的相关性和CBF调节量的表达，CBF调节剂是一套参与冷适应和获得冻结耐受性的基因。因此，我们建议绘制与低R：FR比介导的CBF调节诱导相关的QTL，并与SAS2鉴定的QTL进行比较。