Positional cloning identifies Lotus japonicus NSP2, a putative transcription factor of the GRAS family, required for NIN and ENOD40 gene expression in nodule initiation
Positional cloning identifies Lotus japonicus NSP2, a putative transcription factor of the GRAS family, required for NIN and ENOD40 gene expression in nodule initiation
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DOI：
10.1093/dnares/dsl017
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发表时间：
2006-12-31
期刊：
影响因子：
4.1
通讯作者：
Kawasaki, Shinji
中科院分区：
文献类型：
--
作者：
Murakami, Yasuhiro;Miwa, Hiroki;Kawasaki, Shinji
根瘤菌分泌的Nod-因子（NF）是根瘤形成所必需的。在胚胎发育的早期，基因表达发生了大量的变化。从岐阜B-129生态型中分离到的百脉根nsp 2突变体具有根瘤起始缺陷和非结瘤表型。在这里，我们描述了定位克隆LjNSP 2作为结瘤特异性信号通路的一个组成部分。LjNSP 2被定位在染色体1的易位位点附近，其中重组被严重抑制。为了解决这个问题，我们引入了百脉根（Lotus burttii）作为替代杂交伙伴来代替L。宫古岛。利用11 481株F2代植株构建的高分辨率图谱，结合新开发的DNA标记和BAC文库的构建，使我们能够鉴定出与突变表型相关的基因。LjNSP 2编码GRAS家族的推定转录因子，所述GRAS家族与蒺藜苜蓿NSP 2构成亚家族。LjNSP 2在根和早期结节中表达，但在成熟结节中强烈抑制。Ljnsp 2突变体中NIN和LjENOD 40 -1基因的表达分析表明，LjNSP 2在这些基因的上游发挥作用。这些结果表明，LjNSP 2作为一个转录因子，直接或间接地打开NF诱导的基因所需的结节开始。
Rhizobia-secreted Nod-factors (NFs) are required for nodulation. In the early developmental process of nodulation, a large number of changes occur in gene expression. Lotus japonicus nsp2 mutants isolated from Gifu B-129 ecotype have defects in nodule initiation and display non-nodulating phenotype. Here, we describe positional cloning of LjNSP2 as a component of the nodulation-specific signaling pathway. LjNSP2 was mapped near the translocation site of chromosome 1 where the recombination is severely suppressed. To circumvent this problem, we introduced Lotus burttii as an alternative crossing partner in place of L. japonicus Miyakojima. The development of the high-resolution map using a total of 11 481 F2 plants, in combination with newly developed DNA markers and construction of BAC library, enabled us to identify the gene responsible for mutant phenotype. LjNSP2 encodes a putative transcription factor of the GRAS family that constitutes a subfamily with Medicago truncatula NSP2. LjNSP2 was expressed in roots and early nodules, but strongly suppressed in matured nodules. The expression analysis of NIN and LjENOD40-1 genes in Ljnsp2 mutants indicates that LjNSP2 functions upstream of these genes. These results suggest that LjNSP2 acts as a transcription factor to directly or indirectly switch on the NF-induced genes required for nodule initiation.