Elucidating the spatial and temporal control of granule initiation in wheat

阐明小麦颗粒引发的空间和时间控制

• 批准号: BB/W015935/1
• 负责人: David Seung
• 金额: $ 59.74万
• 依托单位: John Innes Centre
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2022
• 资助国家: 英国
• 起止时间: 2022 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=BB%2FW015935%2F1
• 关键词: Elucidating; spatial; temporal; control; granule

This project aims to develop a full mechanistic understanding of how starch granules are initiated in developing wheat grains. Starch is the main calorific component of our staple cereal crops. It is synthesised in plastids (amyloplasts) of the endosperm as semi-crystalline insoluble granules composed of the glucose polymers, amylopectin and amylose. While the synthesis of these polymers is relatively well understood, we are only beginning to understand how starch granule formation is initiated within plastids, and the factors determining granule shape and size. These traits are important determinants of starch functionality, and thus influence crop quality. Diverse starch granule shapes and sizes are observed across different cereal crops, and this is at least partially determined by differences in granule initiation patterns during grain development. In particular, grains of the Triticeae (wheat, barley, rye) produce two distinct populations of starch granules in the endosperm: large A-type granules, and small B-type granules. These arise from two spatially and temporally separated waves of granule initiation: A-type granules initiate early in grain development in amyloplasts, and B-type granules initiate in late grain development in amyloplast stromules. Our recent research in Arabidopsis leaves identified conserved "initiation proteins" required to initiate the correct number of granules per plastid. Interestingly, we also discovered that these proteins are involved in different aspects of granule initiation in wheat, with some required for correct A-type granule formation, and others for the correct number and timing of B-type granule initiation. How these individual proteins act together in an overall mechanism to orchestrate the initiation of granules during grain development is not understood.We aim to develop a full mechanistic model of the spatial and temporal control of granule initiation in developing wheat grains. In a genetic approach, we will perform crosses using our mutants of tetraploid wheat defective in individual initiation proteins. Starch granule phenotypes will be analysed in the mutants lacking multiple initiation proteins to reveal functional dependencies. In a complementary biochemical approach, we will profile how the abundance and interactions of initiation proteins change through grain development. This will provide an important opportunity to discover and characterise novel components involved in A- and B-type granule initiation. We will also explore the links between granule initiation and amyloplast structure, using live-cell imaging to visualise amyloplast number and structure in our initiation protein mutants. Finally, we will investigate the importance of transcriptional regulation in the temporal control of granule initiation. Preliminary data suggest that initiation proteins follow distinct expression patterns. We will explore how transcript levels of initiation proteins change through grain development, and how this is reflected in protein abundance. An inducible promoter system will be used to alter the timing of initiation protein expression, and subsequent effects on the timing of granule initiations will be examined. We will also attempt to identify candidate transcriptional factors that control the distinct expression patterns of initiation proteins. Overall, our work will reveal mechanisms governing the unique spatiotemporal pattern of granule initiation in wheat, greatly advancing our knowledge of starch synthesis in this important crop. The findings will potentially lead to novel approaches to improve wheat quality by modifying starch granule number and morphology.

该项目旨在全面了解淀粉颗粒在小麦籽粒发育过程中是如何启动的。淀粉是我国主要谷类作物的主要热量成分。它是在胚乳的质体（造淀粉体）中合成的，作为由葡萄糖聚合物、支链淀粉和直链淀粉组成的半结晶不溶性颗粒。虽然这些聚合物的合成是相对较好的理解，我们才刚刚开始了解淀粉颗粒的形成是如何在质体内启动，以及决定颗粒形状和大小的因素。这些性状是淀粉功能的重要决定因素，从而影响作物品质。在不同的谷类作物中观察到不同的淀粉颗粒形状和大小，这至少部分地由谷物发育过程中颗粒起始模式的差异决定。特别地，小麦族（小麦、大麦、黑麦）的谷粒在胚乳中产生两种不同的淀粉粒群体：大的A型颗粒和小的B型颗粒。这些产生于两个空间和时间上分离的波的颗粒起始：A型颗粒在淀粉体中的颗粒发育早期开始，B型颗粒在淀粉体基质中的颗粒发育晚期开始。我们最近在拟南芥叶片中的研究确定了启动每个质体颗粒正确数量所需的保守的“起始蛋白”。有趣的是，我们还发现这些蛋白质参与小麦颗粒起始的不同方面，其中一些是正确的A型颗粒形成所需的，另一些是正确的B型颗粒起始的数量和时间。这些单个蛋白质如何在一个整体机制中共同作用，以协调启动的颗粒在籽粒发育过程中是不理解的。我们的目标是开发一个完整的机制模型的空间和时间控制的颗粒启动在发育中的小麦籽粒。在遗传方法中，我们将使用我们的四倍体小麦突变体进行杂交，这些突变体在单个起始蛋白中有缺陷。淀粉粒表型将在缺乏多种起始蛋白的突变体中进行分析，以揭示功能依赖性。在一个互补的生物化学方法，我们将配置文件如何通过粮食发展的丰度和相互作用的起始蛋白质的变化。这将提供一个重要的机会，发现和发现新的成分参与A型和B型颗粒的启动。我们还将探索颗粒起始和造粉体结构之间的联系，使用活细胞成像可视化造粉体的数量和结构在我们的起始蛋白突变体。最后，我们将调查的重要性，转录调控的时间控制颗粒启动。初步数据表明，起始蛋白遵循不同的表达模式。我们将探讨起始蛋白的转录水平如何通过谷物发育而变化，以及这如何反映在蛋白质丰度中。诱导型启动子系统将用于改变起始蛋白表达的时间，并将检查对颗粒起始时间的后续影响。我们还将尝试确定候选转录因子，控制起始蛋白的不同表达模式。总的来说，我们的工作将揭示小麦颗粒起始独特的时空模式的机制，大大推进我们对这一重要作物淀粉合成的认识。这一发现将为通过改变淀粉颗粒数量和形态来改善小麦品质提供新的途径。

项目成果

Initiation of B-type starch granules in wheat endosperm requires the plastidial a-glucan phosphorylase PHS1

小麦胚乳中 B 型淀粉颗粒的启动需要质体 a-葡聚糖磷酸化酶 PHS1

• DOI: 10.1101/2023.06.01.543270
• 发表时间: 2023
• 作者: Kamble N