Acylation of defence-related natural products in cereals

这项建议涉及了解植物产生的天然产物的合成和功能。天然产物具有重要的生态作用。它们也可能对作物质量产生积极或消极的影响。除了它们在植物中的功能外，它们还被用于商业用途，如药物、染料、调味品、香水和各种其他目的。其中许多化合物具有复杂的化学结构，其合成涉及多个步骤。对植物中自然产物途径的遗传和生化解剖，其中许多是完全没有特征的，是一个巨大的挑战。这项建议涉及天然产物合成的一个特定方面--酰化(向化合物中添加酸性基团的过程)。酰化是植物衍生天然产物的一个共同特征，在生态相互作用中可能会影响这些化合物的生物学性质。酰基也可以作为‘标签’，确保天然产物在植物内的适当运输、封存和储存。最近发现的一类新的植物酶可以将酰基转移到天然产物上，这为研究和操纵天然产物的途径开辟了新的机会。这些酶-丝氨酸羧肽酶样蛋白(SCPL)-与蛋白质降解酶有关。然而，它们不降解蛋白质，而是能够酰化天然产物(即具有酰基转移酶活性)。到目前为止，SCPL酰基转移酶已被证明可以催化野生番茄中抗虫化合物的形成，紫外光保护剂的形成，以及甘蓝中与苦味、收敛和种子油提取问题有关的化合物的形成。然而，它们可能在整个植物新陈代谢中具有更广泛的重要性。最近，我们已经证明，SCPL酰基转移酶是合成抗菌化合物所必需的，这些化合物可以保护燕麦免受疾病侵袭。在这里，我们建议使用化学和生物方法的强大组合来询问这一酰化过程的机制和意义。我们还将研究SCPL酰基转移酶在其他谷物(主要是水稻)植物防御中的广泛意义。

This proposal is concerned with understanding the synthesis and function of natural products that are produced by plants. Natural products have important ecological roles. They can also have positive or negative effects on crop quality. In addition to their functions in plants they are exploited for commercial use as drugs, dyes, flavourings, perfumes and for a variety of other purposes. Many of these compounds have complex chemical structures and their synthesis involves multi-step pathways. The genetic and biochemical dissection of natural product pathways in plants, many of which are completely uncharacterised, represents a substantial challenge. This proposal is concerned with a specific aspect of natural product synthesis - acylation (the process of adding an acidic group to a compound). Acylation is a common feature of plant-derived natural products and is likely to influence the biological properties of these compounds in ecological interactions. Acyl groups may also act as 'tags' that ensure appropriate trafficking, sequestration and storage of natural products within the plant. The recent discovery of a novel class of plant enzymes that transfer acyl groups to natural products has opened up new opportunities for investigation and manipulation of natural product pathways. These enzymes - serine carboxypeptidase-like (SCPL) proteins - are related to protein-degrading enzymes. However they do not degrade proteins and instead are able to acylate natural products (i.e. have acyltransferase activity). So far SCPL acyltransferases have been shown to catalyse the formation of compounds that confer insect resistance in wild tomato, UV protectants in thalecress and compounds associated with bitterness, astringency and seed oil extraction problems in brassicas. However they are likely to have much wider-ranging importance throughout plant metabolism. Recently we have shown that an SCPL acyltransferase is required for the synthesis of antimicrobial compounds that protect oat against disease. Here we propose to use a powerful combination of chemical and biological approaches to interrogate the mechanism and significance of this acylation process. We will also investigate the broader significance of SCPL acyltransferases for plant defence in other cereals (focussing on rice).