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

淀粉是植物中一种重要的碳储能化合物，在工业上和作为人类饮食的一部分有着广泛的用途。通过这个项目，研究人员的目标是更好地了解一种他们怀疑在淀粉代谢中发挥作用和不寻常作用的植物酶的结构和功能。这项研究的潜在长期好处包括含有适合于改良食品和工业应用的淀粉的改良作物。在一些植物中，这种酶是由一个复杂的基因编码的，对它的理解可以帮助我们了解基因是如何进化的。这项研究将在一所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职业做准备。学生们将参与到这项工作的各个方面。此外，该项目将支持一名博士后学者，他将在讲座和入门课程和高级课程的实验室获得宝贵的教学经验，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生研究指导技能，并获得在以本科生为主的机构建立成功职业生涯的实用建议。StARCH是一种复杂的葡萄糖聚合物，主要由支链淀粉组成，支链淀粉是一种高度支化的分子，具有多层短链，长度为12-15个葡萄糖单位。在绿叶中，淀粉在白天积累，在晚上被分解，因此即使在光合作用不活跃的情况下，叶子也可以继续向整个植物输出能量。已知的在淀粉降解中起重要作用的关键酶之一是β-淀粉酶，它能从支链淀粉末端水解二糖麦芽糖。研究人员最近发现，拟南芥中一种名为BAM2的β-淀粉酶不同于所有其他特征的BAMS，因为它是四聚体，需要K+才能发挥活性，具有次级淀粉结合部位，并具有S型动力学。基于这些特性，研究人员提出了一种假说，即BAM2作为修剪酶在淀粉合成中发挥作用，以确保支链淀粉短链具有适当的长度。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，将通过鉴定从野生型和缺乏BAM2的突变植物中分离出来的淀粉的结构来测试该酶的功能。研究人员还将研究BAM2类蛋白在水稻植株中的定位和性质，该蛋白似乎是具有两个假定转录起点的较长BAM7基因的一部分。了解BAM2在淀粉代谢中的作用可能对提高作物淀粉产量的生物技术努力产生重大影响。这里描述的实验可能有助于揭示淀粉结合到BAM2的变构表面如何影响其催化活性。这项工作还可能揭示融合事件如何产生新基因，以及它们如何通过复制和新功能进化。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。

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.