Elucidation of mechanisms required for convergent evolution of secondary metabolite pathways in plants

阐明植物次生代谢途径趋同进化所需的机制

• 批准号: 250496598
• 负责人: Dr. Monika Frey
• 金额: --
• 依托单位: Professur für Pflanzengenetik (aufgelöst)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2014
• 资助国家: 德国
• 起止时间: 2013-12-31 至 2018-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/250496598?language=en
• 关键词: Elucidation; mechanisms; required; convergent; evolution

Plants synthesise a multitude of secondary metabolites. Variability seems to be essential for the function of these Specialised metabolites in communication with the environment and as an arsenal for chemical defence. Establishment of secondary metabolic pathways is based on the common primary metabolism. Specific enzymes are then involved to generate the secondary metabolites, these are e.g. cytochrome P450 monooxygenases, 2-oxoglutarate dependent dioxygenases, methyltransferases, glycosyltransferases. In the genomes large gene families of these modifying enzymes constitute the Toolbox from which unique enzymes are recruited. Little is known about the principles to choose a member of this arsenal, to shape it for the requirements of a distinct step in biosynthesis and to coordinate the reaction sequence. Isolation and comparison of complete sets of biosynthetic genes for pathways that result from convergent evolution will allow getting insight into these mechanisms. Benzoxazinoid biosynthesis is well suited for such an analysis.Benzoxazinoids are defence-related secondary metabolites found in three orders of the angiosperms: Poales, Ranunculales and Lamiales. The complex biosynthesis is biochemically and on gene level (Bx-genes) completely elucidated in maize. All of the 8 biosynthetic genes are located in a cluster, such a genomic organisation has meanwhile been detected for further defence-related biosynthetic pathways. In the grasses the Bx-genes are monophyletic. We have isolated the first gene of the pathway, Bx1, from Consolida orientalis (Ranunculaceae) and Lamium galeobdolon (Lamiaceae). BX1 is a homolog of the alpha-subunit of tryptophan synthase and has been recruited in each of the three orders independently. Recently we could show for C. orientalis that the specific UDP-glucosyltransferase and beta-glucosidase of the pathway evolved by repeated evolution recruiting members of the respective gene families that are non-orthologous to the monocot Bx-gene lineages. No data for these genes are available for the Lamiales.We propose to isolate all missing benzoxazinois-specific genes of C. orientalis and L. galeobdolon. The comparison of the biosynthetic genes of the three orders will reveal preservation of the sequence of reaction steps, possibly existing restrictions for the recruitment of genes out of the given pool, elucidate whether modifications of recruited genes follow a common pattern and whether the formation of a gene cluster parallels for the establishment of the biosynthetic pathway. Candidate genes will be identified by Transcriptomics and verified by functional characterisation in heterologous systems. To get a further independent proof for the isolation of benzoxazinoid-specific genes we intend to establish Virus Induced Gene Silencing, initially for C. orientalis.

植物合成多种二级代谢产物。这些专业代谢产物在与环境交流和化学防御的武器库中的功能似乎至关重要。建立继发代谢途径是基于常见的原代新陈代谢。然后参与特定酶以生成二级代谢产物，例如细胞色素P450单加氧酶，2-氧化甲酸二加氧酶，甲基转移酶，糖基转移酶。在基因组中，这些修饰酶的大基因家族构成了募集独特酶的工具箱。关于选择该武器库的成员的原理知之甚少，以生物合成的独特步骤并协调反应序列的要求。分离和比较由收敛进化而导致的途径的完整生物合成基因集可以深入了解这些机制。苯唑嗪生物合成非常适合这种分析。苯唑嗪类动物是在血管的三个阶段中发现的与防御相关的次生代谢物：Poales，ranunculales and Lamiales。复杂的生物合成在生化上是在玉米中完全阐明的基因水平（BX生成）。所有8种生物合成基因均位于一个集群中，此类基因组组织已被检测到用于进一步的与防御性相关的生物合成途径。在草丛中，BX基因是单系的。我们已经从Consolida Orientalis（Ranunculaceae）和Lamium Galeobdolon（Lamiaceae）分离了途径BX1的第一个基因。 BX1是色氨酸合酶的α-亚基的同源物，并且已独立于三个订单中招募。最近，我们可以向东方梭菌证明，特定的UDP-葡萄糖基转移酶和β-葡萄糖苷酶是通过反复进化的基因家族的反复进化募集成员而演变的，这些基因家族对单核BX-Gene谱系非prother液。我们建议将这些基因的数据用于兰米亚氏菌。我们建议将所有缺失的苯唑诺氏菌特异性基因和galeobdolon的苯唑特异性特异性基因隔离开来。这三个顺序的生物合成基因的比较将揭示反应步骤序列的保存，可能存在从给定池中募集基因的现有限制，阐明了募集基因的修改是否遵循共同的模式以及是否形成了基因群的形成，是否形成了生物合成途径的基因组合。候选基因将通过转录组学鉴定，并通过异源系统中的功能表征验证。为了获得分离苯唑特定基因的进一步独立的证据，我们打算建立病毒诱导的基因沉默，最初是针对东方的。