RUI: Beta-amylases and transitory starch metabolism in Arabidopsis leaves

RUI：拟南芥叶中的β-淀粉酶和短暂淀粉代谢

• 批准号: 1146776
• 负责人: Jonathan Monroe
• 金额: $ 36.96万
• 依托单位: James Madison University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-03-01 至 2017-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1146776&HistoricalAwards=false
• 关键词: RUI; Beta; amylases; transitory; starch

Starch is an important energy-storage compound for plants and it makes up a significant portion of the human diet. In leaves, starch accumulates in chloroplasts during the day, and is broken down at night to provide energy for the plant when photosynthesis is not possible. The enzyme responsible for breaking down most of the starch at night is β-amylase (BAM). There are nine BAM or BAM-like genes in the Arabidopsis genome, six of which (BAM 1, -2, -3, -4, -6 and -9) encode proteins that are targeted to chloroplasts. Of these, only BAM1, -2, -3, and -6 are catalytically active. The focus of this work is on BAM9, which is located in chloroplasts but is catalytically inactive. Preliminary evidence from a mutant lacking BAM9, and from its structure and pattern of expression, suggests that it might play a role in regulating starch metabolism. The three objectives of this work are to 1) investigate the influence of BAM9 on the diurnal activity of the four active plastidic BAMs in leaf extracts of mutants lacking the proteins, 2) characterize the ability of pure BAM9 to bind starch and various small carbohydrates, and 3) identify and characterize protein(s) that bind to BAM9. It is hypothesized that BAM9 acts to inhibit the activity of one or more of the active BAMs at dawn when starch degradation normally stops. This research will help to characterize the physiological functions of five plastid-targeted β-amylases in Arabidopsis, and will shed light on how starch metabolism is regulated in leaves, especially at the night/day transition. The project will also train a number of undergraduates planning to pursue careers in science, and a teaching/research postdoctoral scholar planning to pursue a career at a predominantly undergraduate institution.

淀粉是一种重要的植物储能化合物，在人类饮食中占有相当大的比例。在叶片中，淀粉在白天积累在叶绿体中，在晚上被分解，在光合作用不可能时为植物提供能量。负责在夜间分解大部分淀粉的酶是淀粉酶(BAM)。拟南芥基因组中有9个BAM或BAM类似基因，其中6个(BAM 1、-2、-3、-4、-6和-9)编码以叶绿体为靶标的蛋白质。在这些化合物中，只有BAM1、-2、-3和-6具有催化活性。这项工作的重点是BAM9，它位于叶绿体中，但不具有催化活性。来自BAM9缺失突变体的初步证据，以及它的结构和表达模式，表明它可能在调节淀粉代谢方面发挥作用。本工作的三个目标是：1)研究BAM9对缺失蛋白质突变体叶片提取液中4种活性质型BAMS的影响；2)研究纯BAM9与淀粉和各种小碳水化合物的结合能力；3)鉴定和鉴定与BAM9结合的蛋白(S)。据推测，当淀粉降解正常停止时，BAM9在黎明时抑制一个或多个活性BAMS的活性。这项研究将有助于研究拟南芥中五种以叶绿体为靶标的淀粉酶的生理功能，并将有助于阐明淀粉代谢如何在叶片中调节，特别是在昼夜转换期间。该项目还将培训一批计划从事科学职业的本科生，以及一名计划在以本科生为主的机构从事职业生涯的教学/研究博士后学者。