An Jae Hyung, Lee Hwan Young, Ko Kyoung Nam, Kim Eun-Soo, Kim Yu Sam
Department of Biochemistry, College of Science, Protein Network Research Center, Yonsei University, Seoul, Korea.
Mol Cells. 2002 Oct 31;14(2):261-6.
The role of malonate in symbiotic nitrogen metabolism has long been controversial, although it is known to occur in legume roots, especially in the nodules. Here we report that malonate metabolism plays a key role in the differentiation of bacteroids Rhizobium leguminosarum bv. trifolii in clover nodules. An operon, mat, that consists of three consecutive genes (matABC) has been discovered. Mat encodes enzymes that catalyze the uptake and conversion of malonate to acetyl-CoA through malonyl-CoA. A mutant bacteria, which replaced matB that encodes malonyl-CoA synthetase with a kanamycin resistant gene, was generated and infected with white clover. Clover growth was considerably reduced, even though nodules were formed. However, the nodules were filled with vacuoles, but not with bacteroids. This indicates that malonate metabolism is an important requirement for the formation of mature nodules that are filled with bacteroids.
长期以来，丙二酸在共生氮代谢中的作用一直存在争议，尽管已知它存在于豆科植物根部，尤其是根瘤中。在此我们报告，丙二酸代谢在三叶草根瘤中豆科根瘤菌（Rhizobium leguminosarum bv. trifolii）类菌体的分化中起关键作用。已发现一个由三个连续基因（matABC）组成的操纵子mat。Mat编码通过丙二酰辅酶A催化丙二酸摄取并转化为乙酰辅酶A的酶。构建了一个突变细菌，该细菌用卡那霉素抗性基因取代了编码丙二酰辅酶A合成酶的matB，并感染了白三叶草。尽管形成了根瘤，但三叶草的生长显著减少。然而，这些根瘤充满了液泡，却没有类菌体。这表明丙二酸代谢是形成充满类菌体的成熟根瘤的重要条件。
