Phylogeny and Molecular Evolution of Leguminosae: Nodulation and Nodulin Gene Families

9420215多伊尔利用大气氮而不是更复杂的有机化合物作为氮源的能力是豆科植物(豆科)的一个标志，也是其巨大经济和生态重要性的主要原因。固氮是通过与土壤细菌(“根瘤菌”)合作完成的，土壤细菌(“根瘤菌”)居住在称为根瘤的复杂器官中，通常在豆科植物的根上发现。在根瘤的新特征中，有一套蛋白质(“根瘤蛋白”)是由植物主要或仅在该器官中产生的。许多编码这些蛋白质的基因的起源尚不清楚；建议包括水平转移、基因复制或简单地招募现有基因用于新的目的。系统学和分类学方面的考虑表明，结瘤不止一次起源于豆科植物，然而，根瘤的生物化学和结构复杂性可能会证明只有一个起源，随后是许多独立的结瘤能力丧失。康奈尔大学的杰夫·多伊尔博士正在研究根瘤蛋白编码基因的起源，以检验固氮过程中进化转变的数量。研究的重点是谷氨酰胺合成酶，这是一种在氮素运输中起重要作用的蛋白质，由一个基因家族编码，该基因家族已在几种作物豆类(大豆、紫花苜蓿、菜豆)中进行了研究，但尚未在系统发育距离这些作物更远的豆类中进行研究。主要的分类焦点是结瘤属Chamaecrista及其非结瘤近缘番泻叶属的豆科植物。对迄今为止未被研究的豆科植物结瘤起源的洞察应该有助于阐明这一重要植物生理过程中基因进化的共同机制。?？

9420215 Doyle The ability to use atmospheric nitrogen, rather than more complex organic compounds, as a source of nitrogen is a hallmark of the legume family (Leguminosae, the "beans") and a major cause of its great economic and ecological importance. Nitrogen fixation is accomplished biochemically in partnership with soil bacteria ("rhizobia") which are housed in complex organs termed nodules, usually found on the roots of legumes. Among the novel features of nodules are a suite of proteins ("nodulins") produced by the plant predominantly or exclusively in that organ. The origins of many of the genes encoding many of these proteins are unknown; suggestions have included horizontal transfer, gene duplication, or simply recruitment of existing genes for novel purposes. Phylogenetic and taxonomic considerations suggest that nodulation originated more than once within the legume family of plants, yet the biochemical and structural complexity of the nodule might argue for a single origin followed by many independent losses of the ability to nodulate. Dr. Jeff Doyle of Cornell University is studying the origins of genes encoding nodulin proteins in order to test ideas about the number of evolutionary shifts in nitrogen fixation. Research focuses on glutamine synthetase, a protein with an important role in nitrogen transport, encoded by a gene family that has been studied in several crop legumes (soybean, alfalfa, garden bean) but has yet to be studied in legumes more phylogenetically distant from these. The major taxonomic focus is on legumes of the nodulating genus Chamaecrista and its non-nodulating close relative, Senna. Insights into the origins of nodulation in hitherto unstudied legumes should shed light on common mechanisms of gene evolution in this important plant physiological process. ??