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首页> 外文期刊>Journal of bacteriology >Sinorhizobium meliloti Mutants Deficient in Phosphatidylserine Decarboxylase Accumulate Phosphatidylserine and Are Strongly Affected during Symbiosis with Alfalfa
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Sinorhizobium meliloti Mutants Deficient in Phosphatidylserine Decarboxylase Accumulate Phosphatidylserine and Are Strongly Affected during Symbiosis with Alfalfa

机译：缺乏磷脂酰丝氨酸脱羧酶的中华根瘤菌meliloti突变体积累磷脂酰丝氨酸，并在苜蓿共生期间受到强烈影响。

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Sinorhizobium meliloti contains phosphatidylglycerol, cardiolipin, phosphatidylcholine, and phosphatidylethanolamine (PE) as major membrane lipids. PE is formed in two steps. In the first step, phosphatidylserine synthase (Pss) condenses serine with CDP-diglyceride to form phosphatidylserine (PS), and in the second step, PS is decarboxylated by phosphatidylserine decarboxylase (Psd) to form PE. In this study we identified the sinorhizobial psd gene coding for Psd. A sinorhizobial mutant deficient in psd is unable to form PE but accumulates the anionic phospholipid PS. Properties of PE-deficient mutants lacking either Pss or Psd were compared with those of the S. meliloti wild type. Whereas both PE-deficient mutants grew in a wild-type-like manner on many complex media, they were unable to grow on minimal medium containing high phosphate concentrations. Surprisingly, the psd-deficient mutant could grow on minimal medium containing low concentrations of inorganic phosphate, while the pss-deficient mutant could not. Addition of choline to the minimal medium rescued growth of the pss-deficient mutant, CS111, to some extent but inhibited growth of the psd-deficient mutant, MAV01. When the two distinct PE-deficient mutants were analyzed for their ability to form a nitrogen-fixing root nodule symbiosis with their alfalfa host plant, they behaved strikingly differently. The Pss-deficient mutant, CS111, initiated nodule formation at about the same time point as the wild type but did form about 30% fewer nodules than the wild type. In contrast, the PS-accumulating mutant, MAV01, initiated nodule formation much later than the wild type and formed 90% fewer nodules than the wild type. The few nodules formed by MAV01 seemed to be almost devoid of bacteria and were unable to fix nitrogen. Leaves of alfalfa plants inoculated with the mutant MAV01 were yellowish, indicating that the plants were starved for nitrogen. Therefore, changes in lipid composition, including the accumulation of bacterial PS, prevent the establishment of a nitrogen-fixing root nodule symbiosis.
机译： Sinorhizobium meliloti 含有磷脂酰甘油，心磷脂，磷脂酰胆碱和磷脂酰乙醇胺（PE）作为主要膜脂。 PE分两步形成。第一步，磷脂酰丝氨酸合酶（Pss）将丝氨酸与CDP-甘油二酯缩合形成磷脂酰丝氨酸（PS），第二步，PS被磷脂酰丝氨酸脱羧酶（Psd）脱羧形成PE。在这项研究中，我们确定了编码Psd的鼻窦细菌 psd 基因。缺乏 psd 的鼻窦菌突变体无法形成PE，但会积累阴离子磷脂PS。将缺乏Pss或Psd的PE缺陷突变体的特性与 S的特性进行了比较。 meliloti 野生型。尽管两个PE缺陷突变体都在许多复杂的培养基上以野生型的方式生长，但它们无法在含有高磷酸盐浓度的基本培养基上生长。令人惊讶的是， psd 缺陷型突变体可以在含有低浓度无机磷酸盐的基本培养基上生长，而 pss 缺陷型突变体却不能。在最小培养基中添加胆碱可在一定程度上挽救 pss 缺陷型突变体CS111的生长，但会抑制 psd 缺陷型突变体MAV01的生长。当分析两个不同的PE缺陷型突变体与苜蓿寄主植物形成固氮根瘤共生的能力时，它们的表现却截然不同。缺乏Pss的突变体CS111在大约与野生型相同的时间点启动了结节形成，但确实形成了比野生型少30％的结节。相反，积累PS的突变体MAV01比野生型晚得多地开始结节形成，并且比野生型少结节90％。由MAV01形成的少数结节似乎几乎没有细菌，并且无法固定氮。接种了突变体MAV01的苜蓿植物的叶子是淡黄色的，表明这些植物缺乏氮。因此，脂质组成的变化，包括细菌PS的积累，阻止了固氮根瘤共生的建立。

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