水稻細胞分裂素訊息擬磷酸轉運蛋白在根系發育之功能探討

Functional Analysis of Rice Pseudo Phosphotransfer Proteins (OsPHPs) in Root Development

游勛閎(Xun-Hong YOU)

指導教授 ： 蔡育彰

國立臺灣大學/生物資源暨農學院/農藝學研究所/碩士(2022年)

https://doi.org/10.6342/NTU202203720

摘要

根系的結構與形成在水稻發育中佔有重要地位。根生長分化主要受到植物荷爾蒙所調控，其中細胞分裂素及生長素都是其主要生長調節劑之一。細胞分裂素可經雙分子訊號傳遞系統 (Two-component signal transduction systems, TCSs) 調控訊號，在 TCSs 中磷酸轉運蛋白 (His-phosphotransfer proteins, HPs) 能接受並轉運磷酸訊號至細胞核內，啟動下游細胞分裂素初期反應。水稻具三個擬磷酸轉運蛋白(Pseudo Phosphotransfer Proteins, OsPHPs)，由於缺乏負責傳遞磷酸的組胺酸片段，因此推測這類蛋白在水稻 TCSs 中扮演負向調控角色。OsPHPs 在水稻地下部具有高轉錄表現且會受到外施細胞分裂素及生長素誘導，以 CRISPER/Cas9 基因編輯技術產生 Osphp1/2/3 三重突變株，Osphp1/2/3 相較於野生型株高變矮、主根長縮短、側根數目變少及細胞分裂素降低含量。突變株的 A 型反應調節蛋白 (Type-Aresponse regulator, Type-A RRs)、細胞分裂素氧化蛋白 (CKX) 基因表現與野生型相比表現更多。轉錄體表現分析發現 OsPHPs 除了與細胞分裂素初級反應因子、細胞分裂素之活性調控有關外，也有部分差異表現基因與生長素反應因子相關。在外施生長素處理下，可以觀察到野生型的不定根增加，但在突變株中不定根數目卻受到生長素抑制。此外在外施生長素處理下，Osphp1/2/3 突變株 OsRR2、OsRR4 及轉錄因子OsCRL5 具有較野生型低的基因表現量，推論 OsPHPs 參與生長素調控轉錄因子 OsCRL5 表現，以及影響 OsRR2、OsRR4 表現量增加以抑制細胞分裂素訊號促進不定根發育。由以上結果可知，OsPHPs 藉由負向調控細胞分裂素傳遞影響地下部細胞分裂素含量，並且生長素與細胞分裂素之間的交互作用會共同參與水稻根系發育。

關鍵字

細胞分裂素 ； 水稻 ； 擬磷酸轉運蛋白 ； 根系 ； 生長素

並列摘要

Root system architecture plays an important role in rice development. Root growth and development are mainly regulated by plant hormones, among which cytokinin and auxin are the primary plant growth regulators. Cytokinin can regulate plants through twocomponent signal transduction systems (TCSs). In TCSs, His-phosphotransfer proteins (HPs) can receive and transfer phosphate signals to the nucleus to activate downstream gene response. Three Pseudo Phosphotransfer Proteins (OsPHP1, OsPHP2, and OsPHP3) which lack the conserved His residue are identified in rice. OsPHPs have a high transcriptional expression in rice roots and can be induced by exogenous cytokinin and auxin. Osphp1/2/3 triple mutants were generated using CRISPR/Cas9 genome editing. The mutant had shorter plant height, shorter root length, fewer lateral root numbers, and less cytokinin content than the wild type. The transcription of Type-A response regulators (Type-A RRs) and cytokinin oxidases/dehydrogenases (CKX) were higher in mutants than in wild type. RNA-seq analysis showed that OsPHPs were involved in cytokinin primary response, cytokinin signal regulation, and genes related to auxin response factor. When the exogenous application of auxin treatment, an increase in adventitious roots was observed in the wild type, but there was no increase in the Osphp1/2/3. In addition, the transcript levels of type-A OsRR2, OsRR4, and transcription factor OsCRL5 in Osphp1/2/3 were higher than the wild type in response to exogenous auxin treatment. The results suggested OsPHPs may involve auxin-regulated OsCRL5 signaling and induction of type-A OsRRs to promote adventitious root development. In conclusion, OsPHPs negatively regulate cytokinin signaling and play a role in modulating root development in the crosstalk of cytokinin and auxin.

並列關鍵字

Cytokinin ； Rice ； Pseudo Phosphotransfer Proteins ； Root ； Auxin

參考文獻

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