2019-01-012024-05-17https://scholars.lib.ntu.edu.tw/handle/123456789/671561摘要：叢枝菌根菌為土壤益生真菌，可與80％以上陸生植物共生，其內生菌絲在植物根部皮層細胞裡特化成叢枝狀結構，為植物與真菌養份交換場所，菌根菌提供磷與氮等元素以換取植物的光合產物，為微生物肥料一種，然而，目前對叢枝生命週期及養份交換的調控機制仍不清楚。阿拉伯芥和水稻的研究已知，NITROGEN LIMITATION ADAPTATION (NLA)蛋白參與磷酸運輸蛋白的泛素化並導致其降解；蒺藜苜蓿為牧草作物，亦為豆科模式植物，搜尋其轉錄體資料庫發現三個NLA 同源基因，其中MtNLA-3 表現於含叢枝的皮層細胞內，根據演化的功能保守性及表現位置推測，此基因可能參與調控表現於這類皮層細胞的養份運輸蛋白的穩定性，例如專一表達於此類細胞且負責吸收真菌提供之磷酸的運輸蛋白MtPT4。為詳細剖析蒺藜苜蓿在與菌根菌共生後，MtNLA-3 如何在皮層細胞內調控運輸蛋白之穩定性，此計畫將探討 (1)養份逆境及與叢枝菌根菌共生下MtNLA-3 基因表現的分子特性； (2)分析MtNLA-3在植物與叢枝菌根菌共生關係中扮演之角色，包括調查此基因在根部組織及細胞內的表現位置，利用改變基因表現來探究其在共生關係中的功能，以及對MtPT4 泛素化的影響。預期能對蒺藜苜蓿與叢枝菌根菌共生關係的發展和維持有進一步的了解，以作為提高作物對氮、磷利用效率的研究基礎。<br> Abstract: Arbuscular mycorrhizal fungi (AMF) are beneficial soil microbes. They form mutualistic association with more than 80% vascular land plant species. The intraradical hyphae penetrates the root of host plants and differentiates into highly branched structure called arbuscules in the inner cortical cells as the interface for nutrient exchange. AMF trade mineral nutrients, mainly phosphate and nitrogen, for photosynthetic products from plants. Thus, it is considered as a kind of biofertilizers. However, it is still not clear about the regulatory mechanism of the life span of arbuscules and nutrient exchange between plants and fungi. It has been shown that in Arabidopsis and rice, NITROGEN LIMITATION ADAPTATION (NLA) protein is involved in ubiquitination and degradation of phosphate transporters. Medicago truncatula, a forage crop and model legume as well, have three homologs in the genome. Intriguingly, the M. truncatula transcriptomic data showed that MtNLA-3 was highly expressed in arbuscular cortical cells. Based on the functional conservation in Arabidopsis and rice and its expression site, we hypothesize that MtNLA-3 is involved in the regulation of plant nutrient transporters which are responsible for nutrient exchange in arbuscular cortical cells, such as MtPT4, a phosphate transporter specifically responsible for acquiring fungal phosphate. We hereby propose a 3-year research plan which is composed of two main tasks. First, the molecular features of MtNLA-3 will be characterized in nutrient deficient conditions and AM symbiosis. Second, the functional role of MtNLA-3 in AM symbiosis will be analyzed through different aspects, including phenotyping the transgenic roots with altering MtNLA-3 gene expression, investigating the interaction between MtNLA-3 and MtPT4 and the involvement of MtNLA-3 in ubiquitination of MtPT4. The successful completion of these tasks will unravel the molecular mechanism underlying the development and maintenance of AM symbiosis under nutrient deficiency in M. truncatula, with potential contribution to increase nitrogen and phosphate use efficiency in the future.叢枝菌根菌泛素接合&#37238蒺藜苜蓿arbuscular mycorrhizal fungusubiquitin ligaseMedicago truncatula