RUI: Structure, function and evolutionary history of beta-amylase2 (BAM2) in plants

淀粉是植物中重要的碳和能量储存化合物，在工业和人类饮食中有着广泛的应用。在这个项目中，研究人员旨在更好地了解一种植物酶的结构和功能，他们怀疑这种酶在淀粉代谢中起着不同寻常的作用。这项研究的潜在长期效益包括，含有淀粉的转基因作物具有适合改良食品和工业应用的特性。在一些植物中，这种酶是由一个复杂的基因编码的，对它的理解可以揭示基因是如何进化的。这项研究将在一个以本科生为主的机构进行，涉及至少12名本科生，帮助他们为研究生院和科学事业做好准备。学生们将参与到工作的各个方面。此外，该项目还将支持一名博士后学者，他将获得在入门和高级课程的讲座和实验室的宝贵教学经验，并为实验室带来宝贵的智力和技术资产。最重要的是，他们将能够发展本科研究指导技能，并获得在本科院校建立成功职业生涯的实用建议。淀粉是一种葡萄糖的复杂聚合物，主要由支链淀粉组成，支链淀粉是一种高度分支的分子，具有12-15个葡萄糖单位长的短链层。在绿叶中，淀粉在白天积累，晚上分解，因此即使在光合作用不活跃的时候，叶子也能继续向整个植物输出能量。已知在淀粉降解中起重要作用的关键酶之一是β -淀粉酶，它从支链淀粉的末端水解双糖麦芽糖。研究人员最近发现，拟南芥中有一种被称为BAM2的β -淀粉酶不同于所有其他具有特征的BAM2，因为它是一种四聚体，需要K+才能发挥活性，具有二级淀粉结合位点，并且具有s型动力学。基于这些特性，研究人员提出了一种假设，即BAM2在淀粉合成中起着修剪酶的作用，以确保短链支链具有适当的长度。为了验证这一假设，他们将详细研究野生型和突变型酶的催化和淀粉结合特性。此外，该酶的功能将通过鉴定从缺乏BAM2的野生型和突变型植物中分离的淀粉的结构来进行测试。研究人员还将研究bam2样蛋白在水稻植物中的定位和特性，该蛋白似乎是BAM7基因的一部分，该基因具有两个假定的转录起始位点。了解BAM2在淀粉代谢中的作用可以对提高作物淀粉产量的生物技术努力产生重大影响。本文描述的实验可能揭示淀粉与BAM2变构表面的结合如何影响其催化活性。这项工作还可能揭示新基因是如何通过融合事件产生的，以及它们是如何通过复制和新功能化进化的。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Starch is an important carbon- and energy-storage compound in plants and it has widespread use in industry and as part of the human diet. With this project the researchers aim to better understand the structure and function of a plant enzyme that they suspect plays and unusual role in starch metabolism. Potential long-term benefits of the research include modified crops that contain starch with properties suitable for improved food and industrial applications. In some plants this enzyme is encoded by a complex gene, the understanding of which could shed light on how genes evolve. The research will be carried out at a predominantly undergraduate institution and involve at least 12 undergraduates helping prepare them for graduate school and careers in science. The students will be involved in all aspects of the work. In addition, the project will support a postdoctoral scholar that will obtain valuable teaching experience in lectures and laboratories of introductory and advanced courses, as well as bringing valuable intellectual and technical assets to the lab. Most importantly, they will be able to develop undergraduate research mentoring skills and acquire practical advice for building a successful career at a predominantly undergraduate institution.Starch is a complex polymer of glucose composed mostly of amylopectin, a highly branched molecule with layers of short chains that are 12-15 glucose units long. In green leaves starch accumulates during the day and is broken down at night so that the leaf can continue to export energy to the entire plant even when photosynthesis is not active. One of the key enzymes known to play an important role in starch degradation is beta-amylase, which hydrolyzes the disaccharide maltose from the ends of amylopectin. The researchers recently discovered that one of the beta-amylases in Arabidopsis called BAM2 is unlike all of the other characterized BAMs in that it is a tetramer, requires K+ for activity, possesses a secondary starch-binding site, and has sigmoidal kinetics. Based on these properties the researchers developed a hypothesis that BAM2 plays a role in starch synthesis as a trimming enzyme to ensure that the short amylopectin chains are of the proper length. To test this hypothesis, they will investigate the catalytic and starch-binding properties of the wildtype and mutant enzymes in detail. In addition, the function of the enzyme will be tested by characterizing the structure of starch isolated from wildtype and mutant plants lacking BAM2. The researchers will also investigate the localization and properties of the BAM2-like protein in rice plants that appears to be part of a longer BAM7 gene with two putative transcriptional start sites. Understanding the role of BAM2 in starch metabolism could have a significant impact on biotechnological efforts to enhance starch yield in crops. The experiments described here may shed light on how starch binding to an allosteric surface of BAM2 influences its catalytic activity. The work may also reveal how novel genes can be generated by fusion events and how they can evolve through duplication and neofunctionalization.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.