Department of Molecular Biology, Wageningen University, Wageningen, the Netherlands.
Mol Plant Microbe Interact. 2011 Nov;24(11):1333-44. doi: 10.1094/MPMI-01-11-0013.
A successful nitrogen-fixing symbiosis requires the accommodation of rhizobial bacteria as new organelle-like structures, called symbiosomes, inside the cells of their legume hosts. Two legume mutants that are most strongly impaired in their ability to form symbiosomes are sym1/TE7 in Medicago truncatula and sym33 in Pisum sativum. We have cloned both MtSYM1 and PsSYM33 and show that both encode the recently identified interacting protein of DMI3 (IPD3), an ortholog of Lotus japonicus (Lotus) CYCLOPS. IPD3 and CYCLOPS were shown to interact with DMI3/CCaMK, which encodes a calcium- and calmodulin-dependent kinase that is an essential component of the common symbiotic signaling pathway for both rhizobial and mycorrhizal symbioses. Our data reveal a novel, key role for IPD3 in symbiosome formation and development. We show that MtIPD3 participates in but is not essential for infection thread formation and that MtIPD3 also affects DMI3-induced spontaneous nodule formation upstream of cytokinin signaling. Further, MtIPD3 appears to be required for the expression of a nodule-specific remorin, which controls proper infection thread growth and is essential for symbiosome formation.
成功的固氮共生关系需要将根瘤菌容纳为新的类细胞器结构，称为共生体，在其豆科宿主细胞内。两种在形成共生体能力上受到最强抑制的豆科突变体是 Medicago truncatula 中的 sym1/TE7 和 Pisum sativum 中的 sym33。我们已经克隆了 MtSYM1 和 PsSYM33，并表明两者都编码最近鉴定的 DMI3（IPD3）相互作用蛋白，这是 Lotus japonicus（Lotus）CYCLOPS 的同源物。已证明 IPD3 和 CYCLOPS 与 DMI3/CCaMK 相互作用，后者编码一种钙和钙调蛋白依赖性激酶，是根瘤菌和菌根共生体共同共生信号通路的必需成分。我们的数据揭示了 IPD3 在共生体形成和发育中的新的关键作用。我们表明 MtIPD3 参与但不是感染线程形成所必需的，并且 MtIPD3 还影响细胞分裂素信号转导上游的 DMI3 诱导的自发结瘤形成。此外，MtIPD3 似乎是表达一种特定于根瘤的 remorin 所必需的，该 remorin 控制适当的感染线程生长，对于共生体的形成是必不可少的。
