A new presymbiotic recognition mechanism from cereals enabling root invasion by arbuscular mycorrhizal fungi.

来自谷物的一种新的共生前识别机制，使丛枝菌根真菌能够入侵根部。

• 批准号: BB/Y001133/1
• 负责人: Uta Paszkowski
• 金额: $ 88.79万
• 依托单位: University of Cambridge
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2024
• 资助国家: 英国
• 起止时间: 2024 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=BB%2FY001133%2F1
• 关键词: new; presymbiotic; recognition; mechanism; cereals

Symbioses are fundamental to life on the Earth. One such example, known as arbuscular mycorrhizal (AM) symbiosis, evolved between fungi and plants to facilitate mineral uptake from the soil around 450 mya. This symbiotic arrangement is so widespread that it impacts on ecosystem productivity and global nutrient cycles, and is considered of fundamental importance for crop productivity and sustainability. The development of AM symbioses relies on the well-coordinated exchange of signals to achieve perception and reprogramming of the two interacting organisms. However, due to the complex genetic architecture of the AM fungi, little is known about the components present in the fungus that allow interaction with the plant. Instead, identification and analysis of plant mutants have formed the bedrock of our understanding of molecular processes that underpin the inter-species crosstalk allowing this symbiosis. This proposal centers on presymbiotic signalling to close the gap in our understanding on how perception and reprogramming is achieved to initiate physical plant-fungal engagement in AM symbiosis.Previously, my group had identified the maize mutant independent of arbuscular mycorrhizal symbiosis (ina) that showed a complete early block against fungal root invasion. A unique feature of this mutant is that the defect could be overcome when the fungus was either supported through hyphal connections with wild type plants, or through the addition of wild type root exudates. This suggested that the mutant exudates lacked a critical component. Supported by the BBSRC and in collaboration with the industrial partner Corteva, applying positional cloning and CRISPR/Cas9-based reverse genetics, led to the identification of an essential ABC transporter encoding gene. AM fungi are fatty acid auxotrophs and rely on plants for the provision of lipids. Fully established AM symbioses are marked by the formation of intracellular fungal arbuscules in the inner cortex tissue. It is here where the plant delivers fatty acids to the fungus in exchange for soil minerals. Lipid production is induced in arbuscule-hosting plant cortex cell and exported towards the fungus by a heterodimer of the half-size ABCG transporters Stunted Arbuscule1 and 2 (STR1 and STR2). Consistent with its indispensable role in supporting AM fungi with essential organic carbon, the components of the lipid biosynthetic and delivery pathway are specifically conserved across the mycorrhizal plants in the plant kingdom. Unexpectedly, the maize gene that conditions initial plant-fungal engagement is STR2. STR1 on the other hand, appears not to be involved with the presymbiotic stage since str1 mutants in a variety of plant species show fungal colonisation. On the basis of the strict occurrence of STR2 in genomes of AM-competent plants and the loss of susceptibility of str2 mutants to AM fungi, we hypothesise that STR2 is a core requirement for defining AM host specificity, which would be a ground breaking discovery for this globally prevalent symbiosis.

共生是地球生命的基础。一个这样的例子，称为羊膜菌根（AM）共生，在真菌和植物之间演变，以促进450 Mya左右的土壤矿物质吸收。这种共生的安排非常普遍，以至于它影响生态系统生产力和全球营养周期，并且被认为对作物生产力和可持续性至关重要。 AM共生的发展依赖于信号的良好交换来实现两种相互作用的生物的感知和重编程。但是，由于AM真菌的遗传结构复杂，对真菌中存在的成分允许与植物相互作用的成分知之甚少。取而代之的是，对植物突变体的识别和分析已经形成了我们对基于种体间串扰的分子过程的理解的基础，从而允许这种共生。这项提案以持久性信号传导为中心，以缩小我们对感知和重编程的理解，以启动在AM共生中的物理植物 - 真菌参与。该突变体的一个独特特征是，当真菌通过与野生型植物的菌丝连接或通过添加野生型根渗出液支持真菌时，可以克服缺陷。这表明突变体渗出液缺乏关键成分。在BBSRC并与工业合作伙伴Corteva合作的支持下，采用位置克隆和基于CRISPR/CAS9的反向遗传学，导致鉴定了必需的ABC转运蛋白编码基因。 Am真菌是脂肪酸的富营养，并依靠植物提供脂质。完全建立的AM共生体标志着内皮质组织中细胞内真菌弧菌的形成。在这里，植物将脂肪酸供应到真菌以换取土壤矿物质。脂质产生是在Arbuscule托管植物皮层细胞中诱导的，并通过半尺寸ABCG转运蛋白的异二聚体朝真菌出口，arbcg arbuscule1和2（str1和str2）。与其在基本有机碳支持AM真菌中必不可少的作用一致，脂质生物合成途径和递送途径的组成部分在植物王国的菌根植物中特异性保存。出乎意料的是，调节初始植物摄入量参与的玉米基因是STR2。另一方面，STR1似乎与前自我生物阶段无关，因为各种植物物种中的Str1突变体显示出真菌定殖。根据AM能力植物的基因组中Str2的严格出现以及STR2突变体对AM真菌的敏感性的丧失，我们假设STR2是定义AM宿主特异性的核心要求，这将是这种全球普遍存在的发现的地面破坏发现。