Capela Delphine, Filipe Cédric, Bobik Christine, Batut Jacques, Bruand Claude
Laboratoire des Interactions Plantes-Microorganismes, UMR INRA-CNRS 441-2594, BP52627, 31326 Castanet-Tolosan, France.
Mol Plant Microbe Interact. 2006 Apr;19(4):363-72. doi: 10.1094/MPMI-19-0363.
Sinorhizobium meliloti is a soil bacterium able to induce the formation of nodules on the root of specific legumes, including alfalfa (Medicago sativa). Bacteria colonize nodules through infection threads, invade the plant intracellularly, and ultimately differentiate into bacteroids capable of reducing atmospheric nitrogen to ammonia, which is directly assimilated by the plant. As a first step to describe global changes in gene expression of S. meliloti during the symbiotic process, we used whole genome microarrays to establish the transcriptome profile of bacteria from nodules induced by a bacterial mutant blocked at the infection stage and from wild-type nodules harvested at various timepoints after inoculation. Comparison of these profiles to those of cultured bacteria grown either to log or stationary phase as well as examination of a number of genes with known symbiotic transcription patterns allowed us to correlate global gene-expression patterns to three known steps of symbiotic bacteria bacteroid differentiation, i.e., invading bacteria inside infection threads, young differentiating bacteroids, and fully differentiated, nitrogen-fixing bacteroids. Finally, analysis of individual gene transcription profiles revealed a number of new potential symbiotic genes.
苜蓿中华根瘤菌是一种土壤细菌，能够在包括苜蓿（紫花苜蓿）在内的特定豆科植物根部诱导形成根瘤。细菌通过感染丝定殖于根瘤，在细胞内侵入植物，并最终分化为能够将大气中的氮还原为氨的类菌体，氨可被植物直接同化。作为描述苜蓿中华根瘤菌在共生过程中基因表达全局变化的第一步，我们使用全基因组微阵列来建立由在感染阶段受阻的细菌突变体诱导形成的根瘤中的细菌以及接种后不同时间点收获的野生型根瘤中的细菌的转录组图谱。将这些图谱与对数期或稳定期培养的细菌的图谱进行比较，以及对一些具有已知共生转录模式的基因进行检测，使我们能够将全局基因表达模式与共生细菌类菌体分化的三个已知步骤相关联，即感染丝内的侵入细菌、年轻的分化类菌体和完全分化的固氮类菌体。最后，对单个基因转录图谱的分析揭示了许多新的潜在共生基因。
