Plant and bacterial symbiotic mutants define three transcriptionally distinct stages in the development of the Medicago truncatula/Sinorhizobium meliloti symbiosis
Plant and bacterial symbiotic mutants define three transcriptionally distinct stages in the development of the Medicago truncatula/Sinorhizobium meliloti symbiosis
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DOI：
10.1104/pp.103.031518
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发表时间：
2004-02-01
期刊：
影响因子：
7.4
通讯作者：
Long, SR
中科院分区：
文献类型：
--
作者：
Mitra, RM;Long, SR
在蒺藜苜蓿/苜蓿中华根瘤菌共生中，植物同时经历一系列发育变化，产生根瘤并允许细菌进入和分化。我们对植物基因的研究揭示了在共生建立过程中新的转录调控，并确定了区分植物和细菌共生突变体的分子标记。我们已经确定了三个共生调节植物基因编码β，1-3内切葡聚糖酶（MtBGLU 1），凝集素（MtLEC 4），和含半胱氨酸的蛋白质（MtN 31）。MtBGLU 1在暴露于细菌信号Nod因子后24小时在植物中下调。非诱变植物突变体dmi 1在下调MtBGLU 1的能力上是有缺陷的。分别在细菌接种后1周和2周诱导MtLEC 4和MtN 31。我们研究了这两个基因和三个先前确定的基因（MtCAM 1，ENOD 2，和MtLB 1）在植物共生突变体和野生型植物接种细菌共生突变体的调节。在入侵的初始阶段具有缺陷的植物（bit 1、rit 1和Mtsym 1）和细菌（exoA和exoH）突变体不能诱导MtLEC 4、MtN 31、MtCAM 1、ENOD 2和MtLB 1。固氮缺陷的细菌突变体（fixJ和nifD）和植物突变体的子集（dnj 2、dnf 3、dnf 4、dnf 6和dnf 7）诱导上述基因。巴卡细菌突变体，其沉积到植物细胞后衰老，和两个具有固氮缺陷的植物突变体（dnf 1和dnf 5）诱导MtLEC 4和ENOD 2，但不诱导MtN 31、MtCAM 1或MtLB 1。这些数据表明，存在至少三个转录不同的发展阶段，在入侵M。苜蓿根瘤菌（S.meliloti.）
In the Medicago truncatula/Sinorhizobium meliloti symbiosis, the plant undergoes a series of developmental changes simultaneously, creating a root nodule and allowing bacterial entry and differentiation. Our studies of plant genes reveal novel transcriptional regulation during the establishment of the symbiosis and identify molecular markers that distinguish classes of plant and bacterial symbiotic mutants. We have identified three symbiotically regulated plant genes encoding a beta,1-3 endoglucanase (MtBGLU1), a lectin (MtLEC4), and a cysteine-containing protein (MtN31). MtBGLU1 is down-regulated in the plant 24 h after exposure to the bacterial signal, Nod factor. The non-nodulating plant mutant dmi1 is defective in the ability to down-regulate MtBGLU1. MtLEC4 and MtN31 are induced I and 2 weeks after bacterial inoculation, respectively. We examined the regulation of these two genes and three previously identified genes (MtCAM1, ENOD2, and MtLB1) in plant symbiotic mutants and wild-type plants inoculated with bacterial symbiotic mutants. Plant (bit1, rit1, and Mtsym1) and bacterial (exoA and exoH) mutants with defects in the initial stages of invasion are unable to induce MtLEC4, MtN31, MtCAM1, ENOD2, and MtLB1. Bacterial mutants (fixJ and nifD) and a subset of plant mutants (dnj2, dnf3, dnf4, dnf6, and dnf7) defective for nitrogen fixation induce the above genes. The bacA bacterial mutant, which senesces upon deposition into plant cells, and two plant mutants with defects in nitrogen fixation (dnf1 and dnf5) induce MtLEC4 and ENOD2 but not MtN31, MtCAM1, or MtLB1. These data suggest the presence of at least three transcriptionally distinct developmental stages during invasion of M. truncatula by S.meliloti.