生物谷报道：中国科学院遗传与发育生物学研究所储成才研究组方军博士等在水稻穗发芽研究上取得重要突破，这一研究成果已在国际植物学权威杂志《植物杂志》上发表（Fang J., et al., Plant Journal, Advance Access published on January 16, 2008, doi:10.1111 / j.1365-313X.2008.03411.x）。
众所周知，禾本科作物的穗发芽是世界性的自然灾害。仅在小麦上，我国长江流域冬麦区、东北春麦区、黄淮冬麦区及西南冬麦区等约占全国小麦总面积83% 种植区都发生过严重的穗发芽灾害。1998年，解放军总后勤部嫩江农场两万公顷小麦发生严重穗发芽，受灾面积达100%，造成下年断种而不得不从外地调运。1984年，四川盆地穗发芽损失面积达数十万公顷。这种严重的减产不仅直接影响了生产者的经济利益，而且由于穗发芽引起一系列生理生化变化，严重影响面粉加工利用品质。在水稻上，多年来由于育种更多地考虑高产、优质和抗病虫害指标，往往忽略了种子适度休眠的保留，尤其是杂交水稻制种过程中赤霉素（九二零）的大量使用，导致穗发芽危害严重。我国南方杂交稻制种中，正常年份穗发芽率为5%左右，特殊年份（高温多雨）可超过20%，即使是在常规育种中利用籼粳交培育的高产品种也大多具易穗发芽的弊端。
穗发芽也是环境和植物互作最典型、最复杂的农艺性状之一。目前在禾谷类作物穗发芽机理研究上，虽然科学家以小麦和玉米为材料通过将其作为休眠的对立面开展了一些QTL定位工作，但一直难以从分子机制上进行深入研究。利用玉米突变体也克隆了一些穗发芽相关基因，但由于玉米基因组的复杂性和全基因组测序尚未完成，难以从整体上对穗发芽的分子及生理调控机制进行系统研究。
方军博士等和中国水稻所钱前博士合作通过对大规模水稻突变体库进行系统筛选，获得了12份水稻穗发芽突变体材料，并根据其表型特点将其分成三种类型，《植物杂志》上发表的这篇文章对其中第一种类型突变体的四个穗发芽基因进行了定位和克隆，并对其进行了深入的功能分析，发现这四个基因均定位于类胡萝卜素合成途径。类胡萝卜素不仅是人体不可或缺的营养物质，在植物生长发育中，类胡萝卜素与叶绿素及蛋白质共同构成了类囊体膜上的光系统复合体，并作为叶绿素以外的光合辅助色素在光合作用中起着吸收和传递光能的作用。同时类胡萝卜素也是控制种子休眠的重要激素——脱落酸（ABA）合成的前体。
方军博士等的研究不仅进一步证明了ABA在植物穗发芽中起重要作用，同时通过实验证明了种子中GA/ABA比率变化是造成穗发芽的重要原因。对所有三类突变体的深入研究有望在穗发芽这个重要农艺性状研究上获得重大突破，不仅对解决杂交稻日益严重的穗发芽危害有非常现实的指导作用，对诸如小麦、玉米等其它禾谷类粮食作物穗发芽的控制也有一定的借鉴作用。
生物谷推荐原始出处：
The Plant Journal
OnlineAccepted Articles (Accepted, unedited articles or abstracts published online for future issues)
To cite this article: Jun Fang, Chenglin Chai, Qian Qian, Chunlai Li, Jiuyou Tang, Lei Sun, Zejun Huang, Xiaoli Guo, Changhui Sun, Min Liu, Yan Zhang, Qingtao Lu, Yiqin Wang, Congming Lu, Bin Han, Fan Chen, Zhukuan Cheng, Chengcai Chu
Mutations of genes in synthesis of the carotenoid precursors of ABA lead to preharvest sprouting and photo-oxidation in rice
The Plant Journal (OnlineAccepted Articles).
doi:10.1111/j.1365-313X.2008.03411.x
Mutations of genes in synthesis of the carotenoid precursors of ABA lead to preharvest sprouting and photo-oxidation in rice
Jun Fang1,3*1State Key Laboratory of Plant Genomics and National Centre for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences (CAS), Beijing 100101, China3Graduate University of the CAS, Beijing 100039, China
*These authors contributed equally to this article., Chenglin Chai1,3*1State Key Laboratory of Plant Genomics and National Centre for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences (CAS), Beijing 100101, China3Graduate University of the CAS, Beijing 100039, China
*These authors contributed equally to this article., Qian Qian2*2State Key Laboratory of Rice Biology, China National Rice Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou 310006, China
*These authors contributed equally to this article., Chunlai Li1,31State Key Laboratory of Plant Genomics and National Centre for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences (CAS), Beijing 100101, China3Graduate University of the CAS, Beijing 100039, China, Jiuyou Tang1,31State Key Laboratory of Plant Genomics and National Centre for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences (CAS), Beijing 100101, China3Graduate University of the CAS, Beijing 100039, China, Lei Sun44Centre for Biological Electron Microscopy, Institute of Biophysics, CAS, Beijing 100101, China, Zejun Huang1,31State Key Laboratory of Plant Genomics and National Centre for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences (CAS), Beijing 100101, China3Graduate University of the CAS, Beijing 100039, China, Xiaoli Guo1,31State Key Laboratory of Plant Genomics and National Centre for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences (CAS), Beijing 100101, China3Graduate University of the CAS, Beijing 100039, China, Changhui Sun11State Key Laboratory of Plant Genomics and National Centre for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences (CAS), Beijing 100101, China, Min Liu11State Key Laboratory of Plant Genomics and National Centre for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences (CAS), Beijing 100101, China, Yan Zhang55State Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, CAS, Beijing 100093, China, Qingtao Lu55State Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, CAS, Beijing 100093, China, Yiqin Wang11State Key Laboratory of Plant Genomics and National Centre for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences (CAS), Beijing 100101, China, Congming Lu55State Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, CAS, Beijing 100093, China, Bin Han66National Centre for Gene Research, CAS, Shanghai 200233, China, Fan Chen77Key Laboratory of Developmental Biology, Institute of Genetics and Developmental Biology, CAS, Beijing 100101, China, Zhukuan Cheng11State Key Laboratory of Plant Genomics and National Centre for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences (CAS), Beijing 100101, China, Chengcai Chu11State Key Laboratory of Plant Genomics and National Centre for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences (CAS), Beijing 100101, China 1State Key Laboratory of Plant Genomics and National Centre for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences (CAS), Beijing 100101, China
2State Key Laboratory of Rice Biology, China National Rice Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou 310006, China
3Graduate University of the CAS, Beijing 100039, China
4Centre for Biological Electron Microscopy, Institute of Biophysics, CAS, Beijing 100101, China
5State Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, CAS, Beijing 100093, China
6National Centre for Gene Research, CAS, Shanghai 200233, China
7Key Laboratory of Developmental Biology, Institute of Genetics and Developmental Biology, CAS, Beijing 100101, China
Summary
Preharvest sprouting (PHS) or vivipary in cereals is an important agronomic trait that results in significant economic loss. A considerable number of mutations that cause preharvest sprouting have been identified in several species. However, relatively few viviparous mutants in rice have been reported. To explore the PHS mechanism in rice, we carried out an extensive genetic screening and identified 12 pre-harvest spouting (phs) mutants. Based on their phenotypes, these phs mutants were classified into three groups. Here we characterized in detail one group of them, which contains mutations in genes encoding major enzymes of the carotenoid biosynthesis pathway, including phytoene desaturase (OsPDS), ζ-carotene desaturase (OsZDS), carotenoid isomerase (OsCRTISO) and lycopene β-cyclase (β-OsLCY), which are essential for biosynthesis of carotenoid precursors of ABA. As expected, ABA amount was reduced in all four phs mutants compared to that in wild type. Chlorophyll fluorescence analysis revealed the occurrence of photoinhibition in photosystem and decreased capacity in eliminating excess energy by thermal dissipation. The greatly increased activities of reactive oxygen species (ROS) scavenging enzymes and reduced photosystem (PS) II core proteins CP43, CP47 and D1 in leaves of Oscrtiso/phs3-1mutant and OsLCY RNAi transgenic rice indicated that photooxidative damages occurred in PS II, consistent with the accumulation of ROS in these plants. These results suggest that the impairment in carotenoid biosynthesis causes photo-oxidation and ABA-deficiency phenotypes, of which the latter is a major factor controlling the preharvest sprouting trait in rice.
