OsMYB调控化感水稻酚酸类物质合成及其抑草作用

基因表达调控是水稻化感作用形成的重要基础。本研究对化感水稻PI312777(Oryza sativa L.)的Os MYB(CT829537)基因分别进行过表达(overexpression,OE)和RNA干扰(RNAi),再与稗草(Echinochloa crusgalli,BYG)共培养,以野生型PI312777为对照。结果发现,与稗草共培养下CT829537-OEPI312777的酚类代谢关键酶基因表达上调,根系及其水培液中的总酚酸浓度增加,抑草能力增强;相同处理下CT829537-RNAi PI312777则相反,其酚类代谢关键酶基因较野生型植株表达下调,总酚酸浓度降低,抑草能力下降。这表明Os MYB(CT829537)通过调节化感水稻的酚酸类物质合成进而影响其抑草能力。     

化感水稻不育系‘化57S’田间抑制稗草能力表现评价

评价化感水稻不育系‘化57S’田间抑制稗草能力及稳定性表现及探究其在育种上的研究利用前景。以‘PI312777’和‘化感稻3号’为对照,分3期播种,对5个抑草性状及其稳定性表现进行分析。‘化57S’在3个播期中均表现出良好的抑制稗草能力,其灌浆期抑草率3个播期平均值介于对照‘PI312777’和‘化感稻3号’之间,且差异不显著,其余4个抑草性状在3个播期也均与对照差异不显著;‘化57S’灌浆期抑草率、稗草平均株高和稗草单株干物重3个抑草性状的稳定性均优于2个对照,其中灌浆期抑草率稳定性最好,变异系数仅为4.51%,可作为初步评价‘化57S’化感潜力的一个指标;相关性分析表明,化感作用和竞争作用共同决定化感稻田间整体抑草效果,化感作用主要是抑制稗草萌发,竞争作用既抑制影响稗草存活率又抑制存活稗草的生物量积累、但两者之间相关不明显。化感水稻不育系‘化57S’是一个田间抑制稗草能力较好且部分抑草性状稳定性好的化感稻材料,初步显示出具有良好的研究利用前景。     

不同环境下水稻对受体植物化感作用的动态遗传研究

采用包括基因型与环境互作的数量性状加性—显性发育遗传模型,研究了按双列杂交设计（5×6）/2配制成1套包括亲本、F1 2个世代的水稻遗传材料对受体植物莴苣幼苗根长化感作用的动态遗传及与环境互作效应。遗传方差分析表明,控制水稻不同叶龄期化感作用的加性效应与显性效应呈交替表达趋势,叶龄在7叶期受加性效应控制,在3     

小麦化感作用及其应用

小麦化感作用是利用小麦活体或残体向环境中释放次生代谢物质对自身或其他生物产生作用，它能克服除草剂和杀菌剂等引起的环境污染问题，具有抑制杂草控制病害的潜力。本文对小麦化感作用及其应用作了简要概述。小麦对杂草、虫害及病害产生防御功能的主要化感物质为异羟肟酸和酚酸类物质。小麦化感作用在植物保护、环境保护以及作物育种等方面具有广泛的应用前景，促进了小麦抗逆性的增强以及产量和品质的提高。     

三裂叶蟛蜞菊对水稻化感作用的初步研究

三裂叶蟛蜞菊（Wedelia trilobata L.）是华南地区的重要杂草和园林绿化植物。本文研究了三裂叶蟛蜞菊水提液对水稻（Oryza sativa L.）种子萌发和植株生长过程中一些生理过程的影响。结果表明,三裂叶蟛蜞菊各水提液浸种显著抑制了水稻萌发种子的α-淀粉酶活性和过氧化物酶活性,提高了质膜透性,进而使其活力和呼吸速率显著     

化感水稻抑草作用的根际生物学特性与研究展望

当前水稻化感作用研究主要集中在其遗传生理与分子生态特性和水稻化感物质的分离鉴定及其抑草作用的根际生物学过程与机制两方面。水稻化感作用是个可遗传的数量性状,控制该性状的QTL主要定位在第2、第3、第8、第9、第10染色体上,并存在显著的QTL上位性作用及其与环境的互作效应,但未见控制化感作用性状的QTL遗传信息与何种化感物质的产生紧密相关的研究报道。从现有水稻化感物质的分离鉴定结果看,水稻化感物质可分为三大类,即酚酸类、萜类和黄酮类物质。这三类物质对靶标植物(稗草)均有抑制作用,但酚酸类物质起化感抑草作用的有效浓度较另两类物质的高,且从土壤中检测到的浓度比室内测定的化感抑草作用有效浓度低得多。因此,酚酸类物质是否是一类化感物质经常遭到一些学者的质疑。然而,也有研究结果表明,逆境引起的水稻化感作用潜力增强与其合成酚酸类物质的基因表达增强以及所合成的该类物质分泌释放到根际土壤中的量增多有关。当抑制化感水稻的PAL-2-1基因表达后,其酚酸类物质含量降低,根际微生物数量也随之减少,其中黏细菌属的细菌丰度明显降低,化感抑草效果下降,因而认为在田间条件下化感水稻PAL-2-1基因调控其酚酸类物质合成,经根系分泌进入根际土壤后引起根际特异微生物的趋化性聚集,在这一过程中,释放的根系分泌物可能被土壤中存在的多样性微生物所降解,从而降低其在土壤中的浓度,但正是通过土壤微生物的降解与转化作用,引发了化感物质与根际微生物的藕合效应,并由此产生了水稻化感抑草现象。因此,深入研究这一根际生物学过程对于最终揭示水稻化感作用机理有着极其重要的理论与实际意义。     

水氮互作下长雄野生稻化感作用与田间抑草效果

以化感抗稗草长雄野生稻(Oryza longistaminata),非化感栽培稻RD23以及它们的F₁代(RD23 × O. longistaminata)为材料,采用实验室内生物测定和田间调查相结合方法,研究水肥对长雄野生稻化感作用的影响和探讨对野生稻化感作用及其田间抑制杂草作用的互作关系。在移栽后20~50 d内设淹水、2种形式的干湿交替和旱种等4种田间管理方式,对每种水分管理方式分别设3个施氮(尿素)水平处理。野生稻叶片的水提液,检测了对稗草的化感作用。结果表明,长雄野生稻化感作用在干旱与不施氮水平下最强,对稗草根长与干重的抑制率分别达到69.3%和74.6%,但随着施氮水平的提高与淹水时间的延长而降低;田间则以干湿交替条件下控制稗草效果最好,旱种管理后进行灌水能显著提高野生稻控制稗草的效果。水分与氮互作效应对长雄野生稻化感作用及其田间抑制杂草效果极显著,对F1代化感作用及其田间抑制杂草效果也达显著水平。     

水稻化感品种抑草效应研究

以 PI 312777、丰华占和华粳籼1号为试验材料,研究了在大田抛秧种植条件下对伴生杂草的抑制效应.结果表明,PI 312777与丰华占表现有较强的抑草效应,而华粳籼1号表现不抑草;水稻化感品种的抑草效应主要表现在水稻生长前期,与水稻的化感潜力和水肥条件等方面有关.田间评价结果证明以特征次生物质为标记的方法可以较准确评价水稻品种化感潜力.     

稗草EcHPPD基因的克隆及生物信息学分析

旨在克隆稗草对羟基苯基丙酮酸双氧化酶(HPPD)基因为探究其基因功能提供基础,从而更好地开发除稗剂。以稗草叶片为材料,用同源克隆和c DNA末端快速克隆(RACE)技术克隆Ec HPPD基因序列,用生物信息学软件分析其特征。Ec HPPD基因的编码序列全长1317 bp,其编码蛋白质由439个氨基酸组成,相对分子质量为46.659 k D,等电点为5.30。稗草与同处禾本科的Dichanthelium oligosanthes(OEL23409.1:8-249)的HPPD蛋白进化程度最为相近。Ec HPPD三级建模蛋白结构由两条链构成,有2个Fe²⁺结合位点,并能与吡唑特活性中心骨架通过氢键相互作用。Ec HPPD可能与HGO、HPT1、TAT3、AT5G36160、TAT7等11个蛋白产生互作。本研究报道了Ec HPPD基因序列并对其进行了生物信息学分析,为创制新的HPPD抑制剂提供理论依据。     

水稻圆粒基因RS的鉴定和定位

阐明水稻籽粒大小相关基因的遗传和分子机制对水稻产量形成具有重要意义。利用甲基磺酸乙酯(ethyl methanesulfonate, EMS)诱变粳稻品种宁粳3号筛选获得圆粒突变体round seed (rs)。遗传分析表明,突变体rs圆粒表型由单隐性核基因控制。颖壳扫描电镜观察发现,rs籽粒变圆主要是细胞数目改变导致的。在突变体rs中,细胞周期相关基因的表达较野生型显著升高。将RS定位在第3染色体短臂标记RM3413与N3-5之间,物理距离约589 kb。RS突变影响BR信号途径,改变了粒型相关基因的表达。本研究有助于阐明水稻籽粒发育的分子机制。     

水稻温敏型叶片白化转绿突变体tsa2的表型鉴定与基因定位

水稻温敏型叶色突变体是研究植物光合作用、叶绿体结构和功能以及温度影响叶绿体发育的理想材料。利用甲基磺酸乙酯(EMS)诱变籼型水稻(OryzasativaL.)三系保持系西农1B,从其后代中筛选到一个突变性状稳定遗传的温敏型叶片白化转绿突变体tsa2 (temperature-sensitive green-revertible albino 2)。与野生型相比, tsa2突变表型受温度影响, 22°C条件下萌发的野生型幼苗表型正常,而tsa2幼苗完全白化,且约40%白化苗死亡,存活白化苗的光合色素含量、光合速率均显著降低,成熟期主要农艺性状均显著变劣;在28°C下萌发的tsa2幼苗叶片呈浅绿色并伴有白条纹,其光合色素含量显著降低,光合速率及主要农艺性状差异较小; 32°C下萌发的tsa2幼苗叶片无明显差异。透射电镜观察显示,与野生型相比,tsa2在22°C下叶肉细胞中无叶绿体或存在异常发育叶绿体(尚未分化出基粒和基层),在28°C下部分叶肉细胞含少量发育完整的叶绿体,在32°C下叶肉细胞数量及形态均正常。实时荧光定量PCR(qRT-PCR)分析表明,与野生型相比,tsa2突变体中部分光合色素代谢途径基因、叶绿体发育相关基因及光合作用相关基因的表达水平呈不同程度变化。遗传分析表明, tsa2突变表型受一对隐性核基因控制, TSA2被定位于第5染色体SSR标记S5-57和S5-119之间,物理距离为718 kb。本研究为水稻遗传改良及研究温度影响叶绿体发育机制奠定了基础。     

Trisomic analysis of a strong photoperiod-sensitivity gene E1 in rice (Oryza sativa L.)

Recent genetic analyses on heading-time of rice indicated that almost all the well-adapted varieties in the temperate zone carry a strong photoperiod-sensitivity gene E1, a dominant allele of E1 locus. In order to identify the chromosome on which E1 is located, a trisomic analysis was made using two primary trisomic series originating from the japonica varieties, Nipponbare and Kinmaze, respectively. The Nipponbare and Kinmaze series were crossed with heading-time tester lines, EG0 and EG3, respectively, both of which did not carry the E1. The F2 populations for chromosome 1, 2, and 3 could not be analyzed due to lack of seed. All the other F2 populations showed distinct segregation into early-type and late-type plants caused by the E1 locus segregation, which suggested that the trisomic analysis for E1 locus could be efficiently made. Both disomic and trisomic groups in the F2 population from the cross of the trisomic line for chromosome 7 × EG0 showed a segregation ratio significantly different at the 1% level from a ratio of 1 [e1e1; early]: 3 [E1e1, E1E1; late]. This suggested that E1 was located on chromosome 7. Subsequently, the linkage analysis was made using three morphological marker genes on chromosome 7. It was recognized that E1 was linked to rfs (rolled fine strip gene) and slg (slender glume gene) with recombination values of 16.3 ± 5.88 and 9.1 ± 4.72%, respectively. From these results, it can be concluded that E1 is most likely to be located on chromosome 7. This revised version was published online in July 2006 with corrections to the Cover Date.     

Genetic analysis and fine mapping of LH1 and LH2, a set of complementary genes controlling late heading in rice (Oryza sativa L.)

Heading date in rice (Oryza sativa L.) is a critical agronomic trait with a complex inheritance. To investigate the genetic basis and mechanism of gene interaction in heading date, we conducted genetic analysis on segregation populations derived from crosses among the indica cultivars Bo B, Yuefeng B and Baoxuan 2. A set of dominant complementary genes controlling late heading, designated LH1 and LH2, were detected by molecular marker mapping. Genetic analysis revealed that Baoxuan 2 contains both dominant genes, while Bo B and Yuefeng B each possess either LH1 or LH2. Using larger populations with segregant ratios of 3 : 1, we fine-mapped LH1 to a 63-kb region near the centromere of chromosome 7 flanked by markers RM5436 and RM8034, and LH2 to a 177-kb region on the short arm of chromosome 8 between flanking markers Indel22468-3 and RM25. Some candidate genes were identified through sequencing of Bo B and Yuefeng B in these target regions. Our work provides a solid foundation for further study on gene interaction in heading date and has application in marker-assisted breeding of photosensitive hybrid rice in China.     

Yield of F1, F2 and F3 hybrids of rice (Oryza sativa L.)

Summary Yield and yield components of F₁ hybrids were studied in three experiments at 30×30 cm spacings and in one experiment at 15×15 cm spacings. In the 30×30 cm experiments, 10 of the 41 hybrids tested significantly outyielded their high parents. However, only 2 hybrids significantly outyielded the best cultivar: one hybrid yielded 23 % and the other 16 % more than their respective check cultivars. The four hybrids in the 15×15 cm experiment yielded only 59 to 92% as much as their high parents.In areas where rice is transplanted at relatively wide spacings, the observed levels of F₁ heterosis in selected hybrids may be sufficient to warrant production of hybrid rice, if enough hybrid seed can be produced. For direct-seeding at the high rates normal in the USA, the relatively small levels of heterosis and the difficulties of hybrid seed production preclude use of F₁ hybrid rice cultivars at present.None of 19 bulk F₂ and F₃ hybrids in two experiments yielded significantly more than its high parent. Similarly, none of the 12 mixtures included in one experiment yielded significantly more than its high parent. On the basis of yield alone, using bulk F₂ or F₃ or simple mixture populations is not merited.Contribution from the Western Region, Agricultural Research Service, U.S. Department of Agriculture, and the Department of Agronomy and Range Science, University of California, Davis, California 95616.     

水稻矮化宽叶突变体osdwl1的生理特性和基因定位

株高是影响水稻倒伏的重要因素之一,培育适度矮化水稻品种有利于提高其抗倒性,进而减少产量损失并提高稻米品质,因此研究矮秆形成的分子生理机制具有重要意义。通过辐射诱变籼稻恢复系自选1号获得一个稳定遗传的矮化宽叶突变体osdwl1,本文对其形态与生理特征、细胞结构差异、遗传分析和基因定位等方面进行了研究。大田条件下,osdwl1矮化宽叶性状始于分蘖期后,成熟期穗长和各茎节长度均极显著短于对照,最终导致株高矮化,究其原因,是由于突变体茎节细胞变短所致;而叶片石蜡切片及扫描电镜结果显示,osdwl1的叶片小维管束数及其间距显著增加,从而导致叶片变宽,且其上下表皮的小刺毛数也极显著增加。此外,osdwl1的中上部叶片还表现黄化症状,该性状始于3~4叶期幼苗。生理分析和透射电镜观察表明,与野生型对照相比,孕穗期osdwl1的叶绿体类囊体结构松散,且部分已开始降解,从而导致其倒二叶和倒三叶的叶绿素总含量、净光合速率以及Fv/Fm比值均极显著降低,而其可溶性蛋白、过氧化氢酶及超氧化物歧化酶酶活依次极显著降低,从而导致叶中H2O2及O2-累积,促使丙二醛含量急剧增加。遗传分析表明,osdwl1的矮化宽叶表型受单隐性核基因调控,利用图位克隆技术将该基因定位于6号染色体短臂的SSR标记RM19297与InDel标记ID269-2之间,物理距离为333kb,该结果为进一步克隆OsDWL1基因并研究其功能奠定了基础。     

水稻矮化宽叶突变体osdwl1的生理特性和基因定位

Plant height is one of the important factors affecting rice lodging. The semi-dwarf rice varieties possess high level of lodging resistance, and could reduce yield loss and improve grain quality. Thus, it is very important to study the molecular and physiological mechanism of dwarf formation in rice. In this study, a stable hereditary dwarf and wider-leaf mutant osdwl1 was obtained from ⁶⁰Co γ-radiated indica restore line Zixuan 1, and its morphological and physiological characteristics, cytological observation, genetic analysis and gene mapping were investigated. Under field condition, the mutant osdwl1 exhibited dwarf and wider-leaf after the tillering stage due to shorter length of the parenchyma cells, and its panicle length and all internodes length were significantly shorter compared with wild type plants at mature stage. Paraffin sections and scanning electronic microscopy (SEM) observation revealed that the number of small vascular (SV) bundles and the distance between SVs increased significantly, resulting in wider-leaf blade in osdwl1. Moreover, the number of microhairs on the abaxial and adaxial epidermis were also increased significantly in osdwl1. In addition, starting at the 3-4 leaf seedling stage, yellowing was visible at the upper middle parts of old leaves in osdwl1. Physiological analysis and transmission electron microscopy (TEM) observation indicated that the lamellar structure of chloroplast was distorted and began to collapse in some mesophyll cells, which led to the reduction of total chlorophyll contents, net photosynthetic rate and F_v/F_m ratio of the second and third leaves from top in osdwl1 at the heading stage. Relative to the wild type plants, the soluble protein content, catalase (CAT) and superoxide dismutase (SOD) activities were significantly decreased, which in turn resulting in the accumulation of H₂O₂ and O₂^-, and a steady increase of malondialdehyde (MDA) contents in the mutant leaves. Genetic analysis and gene mapping showed that osdwl1 was controlled by a single recessive nuclear gene, located in a region of 333 kb between SSR marker RM19297 and the InDel marker ID269-2 on the short arm of chromosome 6. The results would further facilitate the cloning and functional analysis of OsDWL1 gene.