中科院植生所植物分子遺傳國家重點實驗室林鴻宣研究員領(lǐng)導(dǎo)的研究組,，在水稻重要性狀遺傳與功能基因研究上又取得重要進展。該研究組通過對水稻耐鹽相關(guān)基因OsHAL3的功能分析,，揭示了光調(diào)控植物發(fā)育的一個新機制。相關(guān)研究論文已于六月二十一日在線發(fā)表于國際著名學(xué)術(shù)雜志《自然-細胞生物學(xué)》(Nature Cell Biology),，并將刊登在7月份期的該雜志上,。這是該研究組自2005年以來，繼分離克隆水稻耐鹽功能基因SKC1,、水稻粒重功能基因GW2和水稻株型馴化基因PROG1之后,，第四次將研究成果發(fā)表在Nature系列雜志上。
植物的生長速度和形態(tài)受到很多環(huán)境因子的影響,，其中陽光是最為重要的一個因子,。在弱光或黑暗的條件下，植物生長速度較快,，形態(tài)幼嫩,；而強光下則反之。這種現(xiàn)象對于植物適應(yīng)光環(huán)境變化,，完成生活史以及提高生物產(chǎn)量具有決定性的意義,，因而一直以來是植物研究的基本問題之一。長期以來,，傳統(tǒng)的光受體調(diào)控機制是解釋這一現(xiàn)象的主流模式,。
HAL3(halotolerance3)是前人在篩選酵母耐鹽基因的過程中分離克隆的抗逆相關(guān)基因，研究發(fā)現(xiàn)其編碼一種促進細胞分裂以及提高耐鹽性的核黃素蛋白,。它的過量表達不僅可以提高植物的耐鹽性,，還可以加速植物的生長。林鴻宣研究員指導(dǎo)博士生孫世勇和晁代印等通過大量的實驗,，對水稻中HAL3同源基因OsHAL3開展了深入的功能和作用機理研究,，發(fā)現(xiàn)這一基因介導(dǎo)了一個與普通光受體模式不同的光控發(fā)育機制。他們的研究證明,，該基因編碼的蛋白以三聚體的形式行使功能,，而陽光，特別是藍光可以促使三聚體解體,，從而導(dǎo)致該蛋白功能失活,；同時，光線還能抑制該基因的表達,。光的這種雙重抑制,，使得細胞分裂減慢，最終導(dǎo)致水稻的生長變緩,。他們的分析還表明,，光照產(chǎn)生的活性氧以及光線對于HAL3配體FMN(flavin mononucleotide，黃素單核苷酸)的直接作用,，可能是三聚體解聚的原因,。進一步的試驗顯示,，HAL3與一種可能參與降解細胞分裂抑制因子的E3泛素連接酶HIP1互作，并激活后者而促進細胞分裂,。而先前發(fā)現(xiàn)的磷酸泛酰半胱氨酸脫羧酶的功能則被證明和其參與的細胞分裂作用不相關(guān),。這一結(jié)果也是第一次發(fā)現(xiàn)HAL3扮演細胞分裂信號傳導(dǎo)的角色。同時,，由于HAL3基因廣泛存在于包括人類在內(nèi)的生物界,，使得這一研究具有更廣泛的意義。
該研究得到國家科技部973項目,、863專項、國家自然基金委和中科院知識創(chuàng)新工程等的資助,。（生物谷Bioon.com）
生物谷推薦原始出處：
Nature Cell Biology 21 June 2009 | doi:10.1038/ncb1892
OsHAL3 mediates a new pathway in the light-regulated growth of rice
Shi-Yong Sun1,4, Dai-Yin Chao1,4, Xin-Min Li1, Min Shi1, Ji-Ping Gao1, Mei-Zhen Zhu1, Hong-Quan Yang1, Sheng Luan2,3 & Hong-Xuan Lin1,2
Plants show distinct morphologies in different light conditions through a process called photomorphogenesis. A predominant feature of photomorphogenesis is the reduced growth of seedlings under light conditions compared with darkness. For this adaptive event, the most well-known molecular mechanism involves photoreceptor-mediated inhibition of cell elongation1, 2, 3, 4. However, it is not known whether additional pathways exist. Here, we describe a newly discovered pathway of light-modulated plant growth mediated by the halotolerance protein HAL3, a flavin mononucleotide (FMN)-binding protein involved in cell division5, 6, 7, 8. We found that light, especially blue light, suppresses growth of rice seedlings by reducing the activity of Oryza sativa (Os) HAL3. Both in vitro and in vivo studies showed that OsHAL3 is structurally inactivated by light through photo-oxidation and by direct interaction with photons. In addition, the transcriptional expression of OsHAL3 is synergistically regulated by different light conditions. Further investigation suggested that OsHAL3 promotes cell division by recruiting a ubiquitin system, rather than by its 4'-phosphopantothenoylcysteine (PPC) decarboxylase activity. Our results uncover a new mechanism for light-regulated plant growth, namely, light not only inhibits cell elongation but also suppresses cell division through HAL3 and E3 ubiquitin ligase. This study thus brings new insights into our understanding of plant photomorphogenesis.
1 National Key Laboratory of Plant Molecular Genetics, Shanghai Institute of Plant Physiology and Ecology, 300 Fenglin Road, Shanghai 200032, China.
2 SIBS-UC Berkeley Center for Molecular Life Sciences, Shanghai Institutes for Biological Sciences (SIBS), Chinese Academy of Sciences, 300 Fenglin Road, Shanghai 200032, China.
3 Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720, USA.
4 These authors contributed equally to this work.
