Duan Guilan, Hakoyama Tsuneo, Kamiya Takehiro, Miwa Hiroki, Lombardo Fabien, Sato Shusei, Tabata Satoshi, Chen Zheng, Watanabe Toshihiro, Shinano Takuro, Fujiwara Toru
State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China.
Graduate School of Agricultural and Life Sciences, The University of Tokyo, Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan.
Plant J. 2017 Jun;90(6):1108-1119. doi: 10.1111/tpj.13532. Epub 2017 Apr 12.
Molybdenum (Mo) is an essential nutrient for plants, and is required for nitrogenase activity of legumes. However, the pathways of Mo uptake from soils and then delivery to the nodules have not been characterized in legumes. In this study, we characterized a high-affinity Mo transporter (LjMOT1) from Lotus japonicus. Mo concentrations in an ethyl methanesulfonate-mutagenized line (ljmot1) decreased by 70-95% compared with wild-type (WT). By comparing the DNA sequences of four AtMOT1 homologs between mutant and WT lines, one point mutation was found in LjMOT1, which altered Trp to a stop codon; no mutation was found in the other homologous genes. The phenotype of Mo concentrations in F progeny from ljmot1 and WT crosses were associated with genotypes of LjMOT1. Introduction of endogenous LjMOT1 to ljmot1 restored Mo accumulation to approximately 60-70% of the WT. Yeast expressing LjMOT1 exhibited high Mo uptake activity, and the K was 182 nm. LjMOT1 was expressed mainly in roots, and its expression was not affected by Mo supply or rhizobium inoculation. Although Mo accumulation in the nodules of ljmot1 was significantly lower than that of WT, it was still high enough for normal nodulation and nitrogenase activity, even for cotyledons-removed ljmot1 plants grown under low Mo conditions, in this case the plant growth was significantly inhibited by Mo deficiency. Our results suggest that LjMOT1 is an essential Mo transporter in L. japonicus for Mo uptake from the soil and growth, but is not for Mo delivery to the nodules.
钼（Mo）是植物必需的营养元素，豆科植物的固氮酶活性需要钼。然而，豆科植物从土壤中吸收钼并将其输送到根瘤的途径尚未明确。在本研究中，我们鉴定了日本百脉根中的一种高亲和力钼转运体（LjMOT1）。与野生型（WT）相比，甲磺酸乙酯诱变系（ljmot1）中的钼浓度降低了70 - 95%。通过比较突变体和野生型品系中四个AtMOT1同源基因的DNA序列，发现LjMOT1中有一个点突变，该突变将色氨酸变为终止密码子；其他同源基因未发现突变。ljmot1和WT杂交后代F中钼浓度的表型与LjMOT1的基因型相关。将内源性LjMOT1导入ljmot1可使钼积累恢复到野生型的约60 - 70%。表达LjMOT1的酵母表现出高钼吸收活性，其K为182 nm。LjMOT1主要在根中表达，其表达不受钼供应或根瘤菌接种的影响。虽然ljmot1根瘤中的钼积累明显低于野生型，但即使是在低钼条件下生长的去除子叶的ljmot1植株，其钼积累仍足以支持正常结瘤和固氮酶活性，在这种情况下，植株生长受到钼缺乏的显著抑制。我们的结果表明，LjMOT1是日本百脉根中从土壤吸收钼并促进生长所必需的钼转运体，但不是将钼输送到根瘤所必需的。
