Cues and mechanisms of daily cell wall thickening

大多数植物的生物量是由包围某些类型细胞的厚壁组成的。树干或玉米秸秆大多是这种形式的次生细胞壁。这种生长是植物质量增加的地方，不同于导致植物体积变化的生长类型，后者是细胞大小变化的结果。材积的增长速度经常在一天中发生变化，其中茎在夜间伸长的速度可能比一天中的任何其他时间都要快得多。植物对温度和光照的日常变化做出反应，它们的生物钟在编排这些节奏的时间方面发挥了作用。这个项目的目标是了解控制细胞壁质量合成的环境线索和调控机制。植物细胞壁生物质是一种丰富的可再生资源，是纸浆和造纸、木材和纺织以及木质纤维生物燃料工业的基石。所获得的知识将使常规育种和生物技术方法能够改善生态和经济上可持续的林业和农业的生产。该项目还将为研究生提供发育、遗传学、基因组学和生物化学方面的跨学科培训，并促进国家聋人技术学院的实习计划。该项目要求用遗传学和生物化学的方法来了解环境条件和控制模式草Brachypodium disachachyon细胞壁生物合成时间的分子机制。我们将提出三个完整的假说：(1)次生壁生物合成是一种特定的时间行为。一些观察结果支持了一种草的模型，在该模型中，细胞伸长和壁厚的速度与时间相反，并受到每日温度变化的影响。植物生物量积累、聚合物前体代谢物和细胞壁基因表达的速率将被量化。(2)基因启动子序列决定了次生细胞壁基因表达的时间。虽然已经报道了几种调节壁生物合成的特定蛋白质-DNA相互作用，但这些序列的存在对基因表达时间的功能结果仍不清楚。这些DNA序列的特定功能将在体内用合成启动子和天然启动子进行研究，使用荧光素酶记者的实时监测。(3)光敏色素蛋白在特定时间的细胞壁增厚中起作用。光敏色素蛋白二聚体是可逆的活性和非活性的，这一过程的速度受到红光/远红光比率和温度的影响。这一机制可能在次生细胞壁基因表达调控和细胞壁增厚节律中发挥作用。野生型B.disachyon和光敏色素突变体将被检测红色/远红光和温度对茎次生壁厚度和相关基因表达的影响。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Most plant biomass is made up of a thick wall that surrounds some types of cell. A tree trunk or a corn stalk are mostly this form of secondary cell wall. This growth, where plants increase in mass, is distinct from the type of growth that results in changes in plant volume which is the result of changes in cell size. The rate of volume growth often changes throughout the day, where stems may elongate much more rapidly at the end of the night than any other time of day. Plants respond to daily changes in temperature and light and their circadian clocks play a role in orchestrating the timing of those rhythms. The goal of this project is to understand the environmental cues and regulatory mechanisms that control the synthesis of cell wall mass. Plant cell wall biomass is an abundant renewable resource and the cornerstone to the pulp and papers, timber and textile, and lignocellulosic biofuel industries. The knowledge gained will enable conventional breeding and biotechnology approaches to improve the production of ecologically and economically sustainable forestry and agriculture. This project will also provide interdisciplinary training in development, genetics, genomics, and biochemistry for graduate students and facilitate an internship program with the National Technical Institute for the Deaf. This project calls for genetic and biochemical approaches to understand the environmental conditions and the molecular mechanisms that control the timing of cell wall biosynthesis in the model grass Brachypodium distachyon. Three integrated hypotheses will be pursued: (1) Secondary wall biosynthesis is a time-of-day specific behavior. Several observations support a model in grasses where the rate of cell elongation and wall thickening is inversely timed and influenced by daily changes in temperature. Rates of plant biomass accumulation, polymer precursor metabolites, and cell wall gene expression will be quantified. (2) Gene promoter sequences determine the timing of secondary cell wall gene expression. Although several specific protein-DNA interactions that regulate wall biosynthesis have been reported, the functional outcome of the presence of these sequences has on the timing of gene expression remains unknown. The specific function of these DNA sequences will be investigated in vivo with synthetic promoters and native promoters using real-time monitoring of luciferase reporters. (3) Phytochrome proteins play a role in time-of-day specific cell wall thickening. Phytochrome protein dimers are reversibly active and inactive, and the rate of that process is influenced by red/far-red light ratios and by temperature. This mechanism may play a role in the regulation of secondary cell wall gene expression and wall thickening rhythms. Wildtype B. distachyon and phytochrome mutants will be examined for the effects of red/far-red light and temperature on stem secondary wall thickness and associated gene expression.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.