首頁 > 科研前沿  > 《Nature》:對獨角金內酯調控水稻分蘗分子機制研究獲突破  
《Nature》:對獨角金內酯調控水稻分蘗分子機制研究獲突破 
作者:中國水稻信息網
來源:中國水稻信息網
發布時間:2013-12-12

2013年12月11日,國際著名刊物Nature以"ARTICLE"形式連續在線發表了我國科學家對獨角金內酯(strigolactones)調控水稻分蘗分子機制研究方面取得的突破性進展。

分蘗,是決定水稻產量的重要農藝性狀之一。它受到遺傳因素的嚴格調控,其主要調控機制是通過植物激素信號通路協調分蘗芽的起始與伸長。長期的研究表明生長素和細胞分裂素是調控株型建成的主要激素。獨角金內酯(strigolactones)是近年來發現的一種植物激素或其前體,能夠抑制植物的分枝(蘗)和側芽的生長,并與生長素和細胞分裂素一起調控植物的分枝(蘗)數量。但該激素如何調控水稻分蘗的分子機理仍不清楚。

在一篇在線發表的題為“DWARF 53 acts as a repressor of strigolactone signalling in rice"論文中,李家洋院士領導的課題組與中科院上海藥物所徐華強課題組、中國水稻研究所(中國農科院)錢前課題組合作,在解析獨角金內酯信號轉導分子機理研究中取得了突破性進展。研究人員發現,D53基因編碼一個double Clp-N motif-containing P-loop nucleoside triphosphate hydrolase, 負調控獨角金內酯信號轉導。分子遺傳學和生化研究表明D53可能與轉錄抑制因子TPR形成復合物,協同抑制獨角金內酯信號通路下游靶基因的表達,從而抑制該信號通路。獨角金內酯誘導D53泛素化并通過蛋白酶體途徑降解,且這一過程依賴于獨角金內酯受體D14和泛素連接酶D3。D53蛋白的降解導致去抑制化,從而激活獨角金內酯信號轉導,精確地調控側芽的伸長。在d53突變體中,D53基因的顯性突變(dominant mutation)使其突變蛋白不能被降解,組成型抑制獨角金內酯信號通路,從而導致d53矮化叢生的表型。獨角金內酯信號轉導的“去抑制化激活”機制與生長素、赤霉素、茉莉酸等重要激素的信號轉導激活機制類似,表明這是植物在進化過程中選擇的一種主要調控模式。

在另一篇在線發表的題為”D14-SCFD3-dependent degradation of D53 regulates strigolactone signalling“論文中,南京農業大學和中國農業科學院作物科學研究所萬建民教授科研團隊及其合作者研究證實了D53蛋白能作為獨腳金內酯信號途徑的抑制子參與調控植物分蘗的生長發育。研究人員利用一個部分顯性水稻矮化多分蘗突變體dwarf 53 (d53),進行外源激素處理和內源激素測定表明,d53是一個獨腳金內酯不敏感突變體。通過精細定位和圖位克隆,獲得了位于水稻第11號染色體短臂末端的D53基因,該基因編碼一個新的在結構上與I類Clp ATPase類似的核蛋白。后續的功能分析發現,在獨腳金內酯存在的條件下D53蛋白可與兩個已知的獨腳金內酯信號分子D14、D3互作,形成D53–D14–SCFD3蛋白復合體,D53蛋白被泛素化,進而特異地被蛋白酶體系統降解,從而誘導下游目標基因的表達以及獨腳金內酯信號的響應。這一結果為通過調控D53基因的表達量,影響獨腳金內酯的信號轉導,從而對水稻分蘗發揮調控作用提供了重要依據。 

Nature同時在NEWS & VIEWS專欄配發題為“Witchcraft and destruction”的專文評述,高度評價我國科學家在這項研究工作的理論意義和潛在應用價值。

論文摘要:DWARF 53 acts as a repressor of strigolactone signalling in rice

Strigolactones (SLs) are a group of newly identified plant hormones that control plant shoot branching. SL signalling requires the hormone-dependent interaction of DWARF 14 (D14), a probable candidate SL receptor, with DWARF 3 (D3), an F-box component of the Skp–Cullin–F-box (SCF) E3 ubiquitin ligase complex. Here we report the characterization of a dominant SL-insensitive rice (Oryza sativa) mutant dwarf 53 (d53) and the cloning of D53, which encodes a substrate of the SCFD3 ubiquitination complex and functions as a repressor of SL signalling. Treatments with GR24, a synthetic SL analogue, cause D53 degradation via the proteasome in a manner that requires D14 and the SCFD3 ubiquitin ligase, whereas the dominant form of D53 is resistant to SL-mediated degradation. Moreover, D53 can interact with transcriptional co-repressors known as TOPLESS-RELATED PROTEINS. Our results suggest a model of SL signalling that involves SL-dependent degradation of the D53 repressor mediated by the D14–D3 complex.

詳細信息:

http://www.cnrri.cn/zjww/Detail.aspx?id=20024641

 

論文摘要: D14-SCFD3-dependent degradation of D53 regulates strigolactone signalling

Strigolactones (SLs), a newly discovered class of carotenoid-derived phytohormones, are essential for developmental processes that shape plant architecture and interactions with parasitic weeds and symbiotic arbuscular mycorrhizal fungi. Despite the rapid progress in elucidating the SL biosynthetic pathway, the perception and signalling mechanisms of SL remain poorly understood. Here we show that DWARF 53 (D53) acts as a repressor of SL signalling and that SLs induce its degradation. We find that the rice (Oryza sativa) d53 mutant, which produces an exaggerated number of tillers compared to wild-type plants, is caused by a gain-of-function mutation and is insensitive to exogenous SL treatment. The D53 gene product shares predicted features with the class I Clp ATPase proteins and can form a complex with the α/β hydrolase protein DWARF 14 (D14) and the F-box protein DWARF 3 (D3), two previously identified signalling components potentially responsible for SL perception. We demonstrate that, in a D14- and D3-dependent manner, SLs induce D53 degradation by the proteasome and abrogate its activity in promoting axillary bud outgrowth. Our combined genetic and biochemical data reveal that D53 acts as a repressor of the SL signalling pathway, whose hormone-induced degradation represents a key molecular link between SL perception and responses.

詳細信息:

http://www.cnrri.cn/zjww/Detail.aspx?id=20024642

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上篇文章:《Nature Genetics》:異三聚體G蛋白調控了水稻的氮利用率
下篇文章:《Nature Communications》:揭示水稻結實率關鍵控制基因
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