The mechanisms of NAD-dependent abiotic stress resilience

作物改良战略要求改良品种具有更强的耐受环境胁迫的能力。BBSRC的粮食安全战略咨询小组在其5年小麦战略建议中建议开发新的性状，以提高可持续性，包括对气候变化和疾病的适应能力。来自我们实验室和其他实验室的数据表明，减少被称为聚ADPR聚合酶（PARP）的酶的活性会使植物对压力处理更具弹性。PARP是多功能酶，因此尚不清楚改变活性如何提高胁迫耐受性。PARP是一类消耗NAD（一种重要的含能量分子）的酶的成员。可能，降低PARP活性会增加植物中NAD的含量，从而提高对压力的适应力。我们将通过测量没有功能性PARP的植物中的NAD水平来测试这一假设。我们的初步数据表明，PARP活性降低所带来的益处并非全部与NAD水平升高相关，因此我们还将测试替代的潜在机制。我们将研究PARP活性对基因表达的调节。我们将确定那些基因的表达改变PARP功能丧失的植物，植物中的酶聚（ADP-核糖）糖水解酶（PARG 1），它抵消PARP活性，减少和植物中的Sirtuin（SRT）的活动改变。SRT是另一类消耗NAD的酶，其活性与PARP交织在一起。我们还将鉴定PARP、PARG 1和SRT结合的DNA区域，因为这将鉴定那些可能是这些酶调节的直接靶点的基因。我们将研究PARP，SRT和PARG 1功能丧失对植物耐受各种胁迫的能力的影响，以及对24小时生物钟功能的影响。将研究这些酶在调节生物钟中的作用，因为生物钟是植物中胁迫信号传导的主要调节剂，并且已经提出与PARP、SRT和PARG 1具有类似功能的酶在生物钟调节中具有作用。在研究了PARP、SRT和PARG对基因表达、应激反应和昼夜信号传导的影响后，我们接下来将着手解决这些影响可能发生的机制。PARP、SRT和PARG 1的活性与染色质的NAD依赖性修饰相关，染色质是一种与DNA结合的蛋白质复合物，参与基因调控。染色质的NAD依赖性化学修饰被认为影响DNA折叠，从而调节基因表达。我们将通过研究HSP 70基因的活性来验证这一假设，HSP 70基因的活性受到结合HSP 70的染色质蛋白的化学修饰的强烈影响。通过研究HSP 70的活性，我们将能够确定PARP、SRT和PARG 1的功能丧失是否对HSP 70活性具有对比效应，正如我们目前的模型所预测的那样。我们还将研究这些酶中的每一种的损失对植物的化学含量的影响，即所谓的代谢组，以确定改变NAD消耗酶活性的作用机制和潜在的农业效益。我们已经成立了一个国际性的多学科小组，以解决被认为有助于胁迫耐受性的一组主要酶的功能和作用机制。我们将联合收割机与剑桥实验室的学术卓越性、德国戈尔姆世界领先的化学分析平台以及根特拜耳作物科学的工业合作伙伴提供的工业资源基础和转化为真实的世界解决方案的潜力相结合。

Crop improvement strategies require improved varieties with increased ability to tolerate environmental stresses. BBSRC's Food Security Strategy Advisory Panel in its advice for a 5-year Wheat Strategy recommended development of new traits for improved sustainability which include resilience to climatic variation and disease. Data from our laboratories and others demonstrate that reduction in the activity of enzymes called poly ADPR polymerases (PARPs) results in plants more resilient to stressful treatments. PARPs are multifunctional enzymes and thus it is not clear how altered activity improves stress tolerance. PARPs are members of a class of enzymes that consume NAD, an important energy containing molecule. Possibly, reducing PARP activity increases the amount of NAD in the plant, resulting in more resilience to stress. We will test this hypothesis by measuring NAD levels in plants with no functional PARPs. Our preliminary data suggest that not all the benefits conferred by reduced PARP activity are associated with increased NAD levels and therefore we will also test alternative potential mechanisms. We will investigate the regulation of gene expression by PARP activity. We will identify those genes whose expression is altered in PARP loss-of-function plants, also plants in which an enzyme Poly(ADP-ribose) glycohydrolases (PARG1), which counteracts PARP activity, is reduced and in plants with altered Sirtuin (SRT) activity. SRTs are another class of NAD consuming enzymes whose activity is intertwined with the PARPs. We will also identify the regions of DNA bound by the PARPs, PARG1 and SRTs, since this will identify those genes that are likely to be the direct targets for regulation by these enzymes. We will investigate the effect of loss-of-function of the PARPs, SRTs and PARG1 on the ability of plants to tolerate a wide range of stresses and also the consequence for the functioning of the 24 hour circadian clock. The role of these enzymes in regulating the circadian clock will be investigated because the circadian clock is major regulator of stress signalling in plants and it has been proposed that enzymes with similar function to the PARPs, SRTs and PARG1 have a role in circadian regulation. Having investigated the effects of PARPs, SRTs and PARGs on gene expression, stress responses and circadian signalling, we will next proceed to addressing the mechanism by which these effects might occur. The activity of the PARPs, SRTs and PARG1 are associated with NAD-dependent modification of chromatin, a complex of proteins bound to the DNA that participates in gene regulation. It is thought that NAD-dependent chemical modifications of chromatin affect DNA folding and thereby regulate gene expression. We will test this hypothesis by studying the activity of the HSP70 gene, which is strongly affected by chemical modifications to the chromatin proteins that bind HSP70. By studying the activity of HSP70 we will be able to determine if loss of function of the PARPs, SRTs and PARG1 has contrasting effects on HSP70 activity, as is predicted by our current models. We also will investigate the effect of loss of each of these enzymes on the chemical content of the plants, the so called metabolome, to identify mechanisms of action and also potential agricultural benefit in altering NAD-consuming enzyme activity. We have formed an international, multidisciplinary group to address the function and mechanism of action of a major group of enzymes that are thought to contribute to stress tolerance. We combine the academic excellence of laboratories in Cambridge, with world-leading chemical analysis platforms in Golm, Germany and the industrial resource base and potential for translation to real world solutions offered by our industrial partners at Bayer CropScience, Ghent.