The Thiamine Biosynthesis Gene THI1 Promotes Nodule Growth and Seed Maturation
The Thiamine Biosynthesis Gene THI1 Promotes Nodule Growth and Seed Maturation
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DOI：
10.1104/pp.16.01254
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发表时间：
2016-11-01
期刊：
影响因子：
7.4
通讯作者：
Takeda, Naoya
中科院分区：
文献类型：
--
作者：
Nagae, Miwa;Parniske, Martin;Takeda, Naoya
硫胺素（维生素B1）是生物体所必需的。与动物不同，植物可以合成硫胺素。在百脉根中，两个硫胺素生物合成基因THI 1和THIC的表达通过接种根瘤菌而增强，但不通过接种丛枝菌根真菌。THIC和THI 2（THI 1的一种寄生物）在未接种的叶片中表达。THI 2基因敲除的植物和转座子插入突变体thiC具有褪绿的叶片。这种典型的硫胺素缺乏症的表型是由外源性硫胺素供应拯救的。在野生型植物中，THI 1主要在根和根瘤中表达，并且即使在没有外源硫胺素的情况下，thi 1突变体也具有绿色叶。THI 1在根瘤原基的活跃分裂细胞中高度表达。thi 1突变体有小结节，这种表型被外源硫胺素和THI 1互补拯救。外源硫胺素增加根瘤直径，但在thi 1突变体或外源硫胺素的丛枝菌根定植水平不受影响。共生标记基因的表达诱导正常，这意味着主要是根瘤生长延迟在thi 1突变体。此外，该突变体形成了许多未成熟的种子，种子重量减少。这些结果表明，由THI 1介导的硫胺素生物合成增强了结节的扩大，并且是L.种子发育所需的。- 是的
Thiamine (vitamin B1) is essential for living organisms. Unlike animals, plants can synthesize thiamine. In Lotus japonicus, the expression of two thiamine biosynthesis genes, THI1 and THIC, was enhanced by inoculation with rhizobia but not by inoculation with arbuscular mycorrhizal fungi. THIC and THI2 (a THI1 paralog) were expressed in uninoculated leaves. THI2-knockdown plants and the transposon insertion mutant thiC had chlorotic leaves. This typical phenotype of thiamine deficiency was rescued by an exogenous supply of thiamine. In wild-type plants, THI1 was expressed mainly in roots and nodules, and the thi1 mutant had green leaves even in the absence of exogenous thiamine. THI1 was highly expressed in actively dividing cells of nodule primordia. The thi1 mutant had small nodules, and this phenotype was rescued by exogenous thiamine and by THI1 complementation. Exogenous thiamine increased nodule diameter, but the level of arbuscular mycorrhizal colonization was unaffected in the thi1 mutant or by exogenous thiamine. Expression of symbiotic marker genes was induced normally, implying that mainly nodule growth was delayed in the thi1 mutant. Furthermore, this mutant formed many immature seeds with reduced seed weight. These results indicate that thiamine biosynthesis mediated by THI1 enhances nodule enlargement and is required for seed development in L. japonicus.