Auxotrophy Accounts for Nodulation Defect of Most Sinorhizobium meliloti Mutants in the Branched-Chain Amino Acid Biosynthesis Pathway
Auxotrophy Accounts for Nodulation Defect of Most Sinorhizobium meliloti Mutants in the Branched-Chain Amino Acid Biosynthesis Pathway
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DOI：
10.1094/mpmi-21-9-1232
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发表时间：
2008-09-01
影响因子：
3.5
通讯作者：
Capela, Delphine
中科院分区：
文献类型：
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作者：
Peltzer, Maria de Las Nieves;Roques, Nicolas;Capela, Delphine
一些与异亮氨酸、缬氨酸和亮氨酸生物合成有关的基因中的苜蓿中华根瘤菌突变体先前被描述为不能在宿主植物上诱导根瘤形成。在这里，我们重新评估了苜蓿根瘤菌中支链氨基酸生物合成途径和结瘤过程之间的相互关系。我们对两个密切相关的苜蓿中华草菌株 1021 和 2011 中异亮氨酸、缬氨酸或亮氨酸营养缺陷型的七个突变体的共生表型进行了表征。我们发现所有突变体在紫花苜蓿宿主植物的结瘤和感染方面均受到类似的损害。在大多数情况下，通过向植物生长培养基中添加缺失的氨基酸可以完全恢复结瘤表型。这强烈表明营养缺陷型是这些突变体结瘤缺陷的原因。然而，我们证实了先前的发现，即苜蓿中华根瘤菌1021遗传背景中的ilvC和ilvD2突变体不能通过补充外源氨基酸来恢复结瘤，即使它们的Nod因子产生似乎是正常的。
Some Sinorhizobium meliloti mutants in genes involved in isoleucine, valine, and leucine biosynthesis were previously described as being unable to induce nodule formation on host plants. Here, we present a reappraisal of the interconnection between the branched-chain amino acid biosynthesis pathway and the nodulation process in S. meliloti. We characterized the symbiotic phenotype of seven mutants that are auxotrophic for isoleucine, valine, or leucine in two closely related S. meliloti strains, 1021 and 2011. We showed that all mutants were similarly impaired for nodulation and infection of the Medicago sativa host plant. In most cases, the nodulation phenotype was fully restored by the addition of the missing amino acids to the plant growth medium. This strongly suggests that auxotrophy is the cause of the nodulation defect of these mutants. However, we confirmed previous findings that ilvC and ilvD2 mutants in the S. meliloti 1021 genetic background could not be restored to nodulation by supplementation with exogenous amino acids even though their Nod factor production appeared to be normal.