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.

植物合成多种次生代谢物。变异性似乎对于这些特殊代谢物与环境沟通以及作为化学防御武器库的功能至关重要。次级代谢途径的建立是基于共同的初级代谢。然后特定的酶参与产生次级代谢产物，例如细胞色素 P450 单加氧酶、2-酮戊二酸依赖性双加氧酶、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工具箱，从中可以招募独特的酶。关于选择该武器库的成员、根据生物合成中独特步骤的要求来塑造它以及协调反应序列的原则，人们知之甚少。分离和比较趋同进化产生的路径的完整生物合成基因组将有助于深入了解这些机制。苯并恶嗪类生物合成非常适合此类分析。苯并恶嗪类是在被子植物三个目中发现的与防御相关的次生代谢产物：禾本科、毛茛目和唇形目。玉米中复杂的生物合成在生物化学和基因水平（Bx 基因）上得到了完全阐明。所有 8 个生物合成基因都位于一个簇中，同时检测到这样的基因组组织以用于进一步的防御相关生物合成途径。在禾本科植物中，Bx 基因是单系的。我们从Consolida orientalis（毛茛科）和Lamium galeobdolon（唇形科）中分离出了该途径的第一个基因Bx1。 BX1 是色氨酸合酶 α 亚基的同源物，并且已在三个目中的每一个中独立招募。最近，我们可以证明侧柏的特定 UDP-葡萄糖基转移酶和 β-葡萄糖苷酶是通过重复进化招募与单子叶植物 Bx 基因谱系非直系同源的各自基因家族的成员而进化的。没有关于 Lamiales 的这些基因的数据。我们建议分离 C. orientalis 和 L. galeobdolon 的所有缺失的苯并恶嗪特异性基因。三个目生物合成基因的比较将揭示反应步骤顺序的保留，从给定池中招募基因可能存在的限制，阐明所招募基因的修饰是否遵循共同模式以及是否形成基因簇平行于生物合成途径的建立。候选基因将通过转录组学进行鉴定，并通过异源系统中的功能表征进行验证。为了获得分离苯并恶嗪类特异性基因的进一步独立证据，我们打算首先针对东方侧柏建立病毒诱导的基因沉默。