Department of Molecular and Cellular Biology, University of California, Davis, California 95616, USA.
Plant Physiol. 2013 Jan;161(1):556-67. doi: 10.1104/pp.112.206110. Epub 2012 Nov 7.
Nodulation in legumes requires the recognition of rhizobially made Nod factors. Genetic studies have revealed that the perception of Nod factors involves LysM domain receptor-like kinases, while biochemical approaches have identified LECTIN NUCLEOTIDE PHOSPHOHYDROLASE (LNP) as a Nod factor-binding protein. Here, we show that antisense inhibition of LNP blocks nodulation in Lotus japonicus. This absence of nodulation was due to a defect in Nod factor signaling based on the observations that the early nodulation gene NODULE INCEPTION was not induced and that both Nod factor-induced perinuclear calcium spiking and calcium influx at the root hair tip were blocked. However, Nod factor did induce root hair deformation in the LNP antisense lines. LNP is also required for infection by the mycorrhizal fungus Glomus intraradices, suggesting that LNP plays a role in the common signaling pathway shared by the rhizobial and mycorrhizal symbioses. Taken together, these observations indicate that LNP acts at a novel position in the early stages of symbiosis signaling. We propose that LNP functions at the earliest stage of the common nodulation and mycorrhization symbiosis signaling pathway downstream of the Nod factor receptors; it may act either by influencing signaling via changes in external nucleotides or in conjunction with the LysM receptor-like kinases for recognition of Nod factor.
豆科植物的结瘤作用需要识别根瘤菌产生的结瘤因子。遗传研究表明，结瘤因子的感知涉及 LysM 结构域受体样激酶，而生化方法已经确定 LECTIN NUCLEOTIDE PHOSPHOHYDROLASE (LNP) 是一种结瘤因子结合蛋白。在这里，我们表明 LNP 的反义抑制阻止了日本甘草的结瘤。这种缺乏结瘤作用是由于结瘤因子信号的缺陷所致，这是基于早期结瘤基因 NODULE INCEPTION 没有被诱导的观察结果，以及核周钙离子爆发和根毛尖端钙离子内流都被阻断。然而，结瘤因子确实诱导了 LNP 反义系的根毛变形。LNP 也被共生真菌 Glomus intraradices 的感染所必需，这表明 LNP 在根瘤菌和菌根共生共有的共同信号通路中发挥作用。综上所述，这些观察结果表明 LNP 在共生信号的早期阶段发挥作用。我们提出 LNP 在结瘤和菌根共生信号通路的早期阶段发挥作用，位于 Nod 因子受体的下游；它可能通过改变外部核苷酸的信号传递或与 LysM 受体样激酶一起识别 Nod 因子来发挥作用。
