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首页> 外文期刊>Journal of Theoretical Biology >Developmental genetics and evolution of symbiotic structures in nitrogen-fixing nodules and arbuscular mycorrhiza.
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Developmental genetics and evolution of symbiotic structures in nitrogen-fixing nodules and arbuscular mycorrhiza.

机译：固氮结核和丛枝菌根中共生结构的发育遗传学和进化。

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Genetic and molecular mechanisms of development are compared for two major plant-microbe endosymbioses: N(2)-fixing nodules (with rhizobia or actinomycetes Frankia) and arbuscular mycorrhiza (with Glomales fungi). Development from the primordia formed de novo in root tissues is common for all known types of N(2)-fixing nodules. However, their structure varies greatly with respect to: (i) tissue topology (location of vascular bundles is peripherical in legumes or central in non-legumes); (ii) position of nodule primordium (inner or outer cortex in legumes, pericycle in non-legumes); (iii) stability of apical meristem (persistent in the indeterminate nodules, transient in the determinate ones). In addition, legumes vary in ability to form compartments harboring endosymbiotic rhizobia and located intercellularly (infection threads) and intracellularly (symbiosomes). Using pea (Pisum sativum) symbiotic mutants, the nodule developmental program is dissected into a range of spatially and temporarily differentiated steps comprising four sub-programs (development of endosymbiotic compartments; nodule histogenesis; autoregulation of nodulation; bacteroid differentiation). The developmental mutations are suggested in some cases to reverse the endosymbiotic system into the morphologically simpler forms some of which may correspond to the ancestral stages of nodule evolution. The origin of legume-rhizobial and actinorhizal symbioses is suggested to be based on a set of preadaptations many of which had been evolved in angiosperms during coevolution with arbuscular mycorrhizal fungi (e.g., inter- and intracellular maintenance of symbionts, their control via defence-like reactions and recognition of chitin-like molecules). An analysis of parallel morphological variation in symbiotic mutants and wild-growing legume species enables us to reconstruct the major stages of evolution for N(2)-fixing symbioses. Copyright 2002 Academic Press.
机译：比较了两个主要植物-微生物内共生体的发育的遗传和分子机制：N（2）-固定结节（有根瘤菌或放线菌弗兰基亚）和丛枝菌根（有Glomales真菌）。对于所有已知类型的N（2）固定结节，从根组织中从头形成的原基发育都是常见的。但是，它们的结构在以下方面有很大不同：（i）组织拓扑结构（豆科植物中血管束的位置是周围的，非豆类中的血管束的位置是中心的）; （ii）结节原基的位置（豆类的内部或外部皮层，非豆类的围生周期）; （iii）顶端分生组织的稳定性（持续存在于不确定的结节中，短暂存在于确定的结节中）。另外，豆类植物形成具有内共生根瘤菌并且位于细胞间（感染线）和细胞内（共生体）的区室的能力各不相同。使用豌豆（Pisum sativum）共生突变体，将结节发育程序分为一系列空间和临时区分的步骤，这些步骤包括四个子程序（共生共生区室的发育;结节组织发生;结节的自动调节;类细菌分化）。在某些情况下，建议发育突变将内共生系统逆转为形态上更简单的形式，其中某些形式可能与结节进化的祖先阶段相对应。豆科植物的根瘤菌和放线菌共生的起源被认为是基于一系列的适应性变化，其中许多与丛枝菌根真菌共进化过程中在被子植物中已经进化了（例如，共生和细胞内维持共生，通过类似防御的方式进行控制）。反应和对几丁质样分子的识别）。对共生突变体和野生豆类物种中平行形态变异的分析使我们能够重建固定N（2）共生酶的进化的主要阶段。版权所有2002学术出版社。

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