Identification of a novel tillering dwarf mutant and fine mapping of the TDDL（T） gene in rice （Oryza sativa L.）

Rice plant architecture is an important agronomic trait that affects the grain yield. To understand the molecular mechanism that controls plant architecture, a tillering dwarf mutant with darker-green leaves derived from an indica cultivar IR64 treated with EMS is characterized. The mutant, designated as tddl（t）, is nonallelic to the known tiilering dwarf mutants. It is controlled by one recessive nuclear gene, TDDL（T）, and grouped into the dn-type dwarfism according to Takeda＇s definition. The dwarfism of the mutant is independent of gibberellic acid based on the analyses of two GA-mediated processes. The independence of brassinosteroid （BR） and naphthal-3-acetic acid （NAA） of the tddl（t） mutant, together with the decreased size of parenchyma cells in the vascular bundle, indicates that the TDDL（7） gene might participate in another hormone pathway. TDDL（T） is fine mapped within an 85.51 kb region on the long arm of rice chromosome 4, where 20 ORFs are predicted by RiceGAAS （http：//ricegaas.dna.affrc. go.jp/rgadb/）. Further cloning of TDDL（T） will benefit both marker assisted selection （MAS） of plant architecture and dissection of the molecular mechanism underlying tillering dwarf in rice.     

Identification and characterization of a salt tolerance-responsive gene( AtGRP9) of Arabidopsis

Soil salinity is one of the important limiting factors for plant growth and development. A cDNA clone encoding a glycine-rich protein (designated AtGRP9) was identified from Arabidopsis by functional expression of the plant cDNA library in the fission yeast S. pombe. Yeast cells overexpressing AtGRP9 displayed significantly enhanced salt tolerance. Northern analysis showed that expression of AtGRP9 in Arabidopsis was induced by NaCl and plant hormone abscisic acid (ABA). These results suggest that AtGRP9 may be involved in the salt stress response in Arabidopsis.     

Clustered spikelets 4, encoding a putative cytochrome P450 protein CYP724B1, is essential for rice panicle development

Rice （Oryza sativa L.） inflorescence （panicle） architecture is an important agronomic trait, serving as one of the determinants of rice yield. A number of genes related to panicle development have been cloned and functionally characterized so far. However, more information is needed for fully understanding of the mechanism underlying the panicle development. In the present study, we identified a clustered spikelets 4 （cl4） mutant in the 93-11 genetic background. Compared to its wild-type 93-11, cl4 mutant has a typical clustered spikelets phenotype with all primary branches clustered on the base of the main rachis and 2-3 abnormal spikelets clustered on the primary branches. Moreover, cl4 mutant also shows shorter plant height than that of the wild type. Map-based cloning strategy is per- formed to clone the CL4 gene. As a result, CL4 is demonstrated to encode a putative cytochrome P450 protein CYP724B1, which is involved in brassinosteroid biosynthesis. To confirm our mapping result, the CL4 RNAi transgenic plants are generated. And the transgenic plants also show similar phenotype as the cl4 mutant. These results provide strong evidence that CL4 plays an important role in rice panicle development as well as plant height regulation.     

Review and prospect of transgenic rice research

Rice is one of the most important crops as the staple food for more than half of the world＇s population. Rice improvement has achieved remarkable success in the past half-century, with the yield doubled in most parts of the world and even tripled in certain regions, which has contributed greatly to food security globally. Rapid population growth and economic development pose a constantly increased food requirement. However, rice yield has been hovering in the past decade, which is mainly caused by the absence of novel breeding technologies, reduction of genetic diversity of rice cultivars, and serious yield loss due to increasingly severe occurrences of insects, diseases, and abiotic stresses. To address these challenges, Chinese scientists proposed a novel rice breeding goal of developing Green Super Rice to improve rice varieties and realize the sustainable development of agriculture, by focusing on the following 5 classes of traits： insect and disease resistance, drought-tolerance, nutrient-use effi- ciency, quality and yield potential. As a modern breeding approach, transgenic strategy will play an important role in realizing the goal of Green Super Rice. Presently, many transgenic studies of rice have been conducted, and most of target traits are consistent with the goal of Green Super Rice. In this paper, we firstly review technical advances of rice transformation, and then outline the main progress in transgenic rice research with respect to the most important traits： insect and disease-resistance, drought-tolerance, nutrient-use efficiency, quality, yield potential and herbicide-tolerance. The prospects of developing transgenic rice are also discussed.     

Identification and function analysis of spectrin-like protein in pollen tubes of lily （Lilium davidii Duch）

The elongation of pollen tube is an important process of sexual reproduction in higher plant. Cytoskeleton plays a major regulatory role in the elongation of pollen tubes. But whether membrane skeleton is involved in the pollen tube elongation is not clear. In this study, immunochemical detection of spectrin-like protein has been carried out in pollen tubes. By use of 2-dimensional electrophoresis(2DE) and western blotting, two spectrin-like proteins are found, one is 150 kD, and the other is 105 kD, with pl being 4.54 and 4.39, respectively. 150 kD spectrin-like protein is located in plasma membrane of pollen tube and 105 kD spectrin-like protein is located in cytoplasm, probably functioning as a subunit to form a dimmer (210 kD) in vivo. The elongation of pollen tubes is inhibited after spectrin antibody was injected into a growing pollen tube. These results suggest that spectrin-like proteins exist in pollen tube and play an important regulating role in the elongation process of pollen tubes from lily.     

Identification of a novel tillering dwarf mutant and fine mapping of the TDDL(T) gene in rice (Oryza sativa L.)

Rice plant architecture is an important agronomic trait that affects the grain yield. To understand the molecular mechanism that controls plant architecture, a tillering dwarf mutant with darker-green leaves derived from an indica cultivar IR64 treated with EMS is characterized. The mutant, designated as tddl(t), is nonallelic to the known tillering dwarf mutants. It is controlled by one recessive nuclear gene, TDDL(T), and grouped into the dn-type dwarfism according to Takeda’s definition. The dwarfism of ...     

Genetic diversity of rice cultivars （Oryza sativa L.） in China and the temporal trends in recent fifty years

Public concern is often expressed at cultivars because the domestication and modern plant breeding have led to a reduction in the genetic diversity of crops and loss of genes, which could result in crops' genetic vulnerability to changes in the spectrum of pestssity of varieties in this zone is very important to the whole rice production in China. REZV, a important japonica rice production areas with more than 278 thousands ha rice which was about 71% of rice area in north China, accounted fo…     

Estimating genetic diversity and sampling strategy for a wild soybean （Glycine soja） population based on different molecular markers

With the rapid development of the global economy and continued increase in world population, natural environments face serious deterioration and change, which has led to the extinction or severe endangerment of many plant species including important crops…     

Crucial function of histone lysine methylation in plant reproduction

Unlike animals, plants do not set aside germ cells early in development. In angiosperm species, reproduction occurs in the adult plant upon flowering. The multicellular male and female gametophytes differentiate from meiotic products within reproductive floral organs. Double fertilization is another remarkable feature of most angiosperm species. The zygote derived from fertilization of the egg cell by one of the sperm cells and the endosperm from fertilization of the central cell by the second sperm cell develop in a coordinated manner together and enclosed in the sporophytic maternal integuments, forming the seed. Understanding plant reproduction is biologically pertinent and agronomically and ecologically important. Here, we describe the known functions of histone lysine methylations in various steps of reproduction in the reference plant Arabidopsis thaliana. It is emerging that histone lysine methylation is key for understanding epigenetic regulation networks of genome function.     

The coordinated development of China’s inland water transport

The coordinated development is the core of sustainable development, and the hot issue of international research.SInland water transport (IWT) is an important part of the water resources exploiting system and comprehensive transport system under socio-economic context of river basin,and also the country’s sustainable development priorities to achieve resource-conserving and environment-friendly strategy.SThis paper is based on the coordinated development content, combined Germany"s successful development experience, explored the elements and the problem of the coordinated development of IWT system of China’s national economic strategy and basin economy, water resourse system, comprehensive transport system, and system itself, and their countermeasures and suggestions,in order to facilitate rapid and coordinated development of China"s inland water transport.S     

Characterization and mapping of a white panicle mutant gene in rice

A spontaneous white panicle mutant was found from the F6 progenies of an indicajaponica cross.The mutant exhibits white stripes on its basal leaves while the panicles,rachis and pedicel are milky white colored at flowering stage.Genetic analysis in an F2 population from the cross of Zhi7/white panicle mutant indicates that the white panicle phenotype is controlled by a single recessive nuclear gene,tentatively termed as wp(t).Using microsatellite markers,the wp(t) gene was anchored between the markers of SSR101 and SSR63.9 with a map distance of 2.3 and 0.8cM,respectively,and co-segregated with the marker of SSR17 on rice chromosome 1.     

Fine mapping of a semidwarf gene sd-g in indica rice（Oryza sativa L.）

The semidwarf gene sd-g which has been usedin indiea rice breeding in southern China is a new one, non-allelic to sd-1. To map sd-g, an F2 population derived fromthe cross between Xinguiaishuangai and 02428 was con-structed. The sd-g was roughly mapped between two mi-crosatellite markers RM440 and RM163, with genetic dis-tances of 0.5 and 2.5 cM, respectively. Then nine new poly-morphic microsatellite markers were developed in this region.The sd-g was further mapped between two microsatellitemarkers SSR5-1 and SSR5-51, with genetic distances of 0.1and 0.3 cM, respectively, while cosegregated with SSR418. ABAC contig was found to span the sd-g locus, the region be-ing delimited to 85 kb. This result was very useful for cloningof the sd-g gene.     

Characterization and mapping of a lesion mimic mutant in rice （Oryza sativa L.）

A rice initiation-type lesion mimic mutant (lmi) was identified, which was isolated from an indica rice Zhongxian 3037 through γ radiation mutagenesis. Trypan blue staining and sterile culture revealed that the mutant spontaneously developed lesions on the leaves in a developmentally regulated and light-dependent manner. Genetic analysis indicated that the lesion mimic trait was controlled by a single resessive locus. Using public molecular markers and an F2 population derived from lmi and 93-11, we mapped the lmi locus to the short arm of chromosome 8, nearby the centromere, between two SSR markers RM547 and RM331. The genetic distance was 1.2 and 3.2 cM, respectively. Then according to the public rice genomic sequence between the two SSR markers, lmi was further finely tagged by three CAPS markers: C4135-8, C4135-9 and C4135-10. And lmi locus was a co-segregated with marker C4135-10, providing a starting point for lmi gene cloning.     

Isolation and genetic characterization of a fragile plant mutant in rice (itOryza sauva) L.

The fragile rice mutant was isolated from an M₂ population of indica variety Shuang Ke Zao (SKZ) treated with g-rays, and designated as fp1 (fragile plant 1) because of its fragile leaves and culms. To map FP1 locus, an F² mapping population was derived from a cross between the fp1 and C-bao, a polymorphic japonic variety. The primary mapping result places the FP1 locus in an interval between two molecular markers, microsatellite marker RM16 (3.1 cM proximal to FP1) and STS marker G144a (9.1 cM distal to FP1) in the centromere region of chromosome 3. A CAPS marker C524a was further developed between RM16 and G144a, with 0.4 cM genetic distances to the FP1locus, providing a practical starting point for constructing a BAC contig spanning the FP1 locus and cloning the fp1 gene. Allelism test demonstrated that fp1 is allelic to bc1, a fragile rice mutant reported previously.     

水稻紫色柱头突变体ps-5的遗传分析和分子定位

在水稻品种Nipponbare中发现一个紫色柱头突变体ps-5,整个生育期最显著的特点就是柱头紫色且子房较大.遗传分析表明该基因受1对隐性核基因控制,暂命名为ps.利用极端个体定位法把ps-5精细定位于第8染色体SSR标记LR41和LR43之间,ps-5基因距它们的遗传距离均为0.12cM,并与LR413共分离,LR41和LR43两标记间的物理距离约为125kb,为该基因的分子标记辅助选择和图位克隆奠定了基础.     

Genetic analysis and mapping of rice （Oryza sativa L.） male-sterile （OsMS-L） mutant

A rice male-sterile mutant OsMS-L of japonica cultivar 9522 background, was obtained in M4 population treated with ^60Co γ-Ray. Genetic analysis indicated that the male.sterile phenotype was controlled by a single recessive gene. Results of tissue section showed that at microspore stage, OsMS-L tapetum was retarded. Then tapetal calls expanded and microspores degenerated. No matured pollens were observed in OsMS-L anther locus. To map OsMS-L locus, an F2 population was constructed from the cross between the OsMS-L (japonica) and LongTeFu B(indica). Firstly, the OsMS-L locus was roughly mapped between two SSR markers, RM109 and RM7562 on chromosome 2. And then eleven polymorphic markers were developed for further fine fine-mapping. At last the OsMS-L locus was mapped between the two lnDel markers, Lhsl0 and Lhs6 with genetic distance of 0.4 cM, respectively. The region was delimited to 133 kb. All these results were useful for further cloning and functional analysis of OsMS-L.     

Genetic analysis and gene fine mapping of a rolling leaf mutant (<Emphasis Type="Italic">rl</Emphasis><Subscript><Emphasis Type="Italic">11(t)</Emphasis></Subscript>) in rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.)

The exploration of new genes controlling rice leaf shape is an important foundation for rice functional genomics and plant archi-tecture improvement. In the present study, we identified a rolling leaf mutant from indica variety Yuefeng B, named rl_11(t), which exhibited reduced plant height, rolling and narrow leaves. Leaves in rl_11(t) mutant showed abnormal number and morphology of veins compared with those in wild type plants. In addition, rl_11(t) mutant was less sensitive to the inhibitory effect of auxin than the wild type. Genetic analysis suggested that the mutant was controlled by a single recessive gene. Gene Rl_11(t) was initially mapped between SSR markers RM6089 and RM124 on chromosome 4. Thirty-two new STS markers around the Rl_11(t) region were developed for fine mapping. A physical map encompassing the Rl_11(t) locus was constructed and the target gene was finally delimited to a 31.6 kb window between STS4-25 and STS4-26 on BAC AL606645. This provides useful information for cloning of Rl_11(t) gene.     

Genetic analysis and fine mapping of an enclosed panicle mutant esp2 in rice （Oryza sativa L.）

The phenomenon of panicle enclosure in rice is mainly caused by the shortening of uppermost internode.Elucidating the molecular mechanism of panicle enclosure will be helpful for solving the problem of panicle enclosure in male sterile lines and creating new germplasms in rice.We acquired a monogenic recessive enclosed panicle mutant,named as esp2 (enclosed shorter panicle 2),from the tissue culture progeny of indica rice cultivar Minghui-86.In the mutant,panicles were entirely enclosed by flag leaf sheaths and the uppermost internode was almost completely degenerated,but the other internodes did not have obvious changes in length.Genetic analysis indicated that the mutant phenotype was controlled by a recessive gene,which could be steadily inherited and was not affected by genetic background.Apparently,ESP2 is a key gene for the development of uppermost internode in rice.Using an F 2 population of a cross between esp2 and a japonica rice cultivar Xiushui-13 as well as SSR and InDel markers,we fine mapped ESP2 to a 14-kb region on the end of the short arm of chromosome 1.According to the rice genome sequence annotation,only one intact gene exists in this region,namely,a putative phosphatidylserine synthase gene.Sequencing analysis on the mutant and the wild type indicated that this gene was inserted by a 5287-bp retrotransposon sequence.Hence,we took this gene as a candidate of ESP2.The results of this study will facilitate the cloning and functional analysis of ESP2 gene.     

Fine mapping of an incomplete recessive gene for leaf rolling in rice （Oryza sativa L.）

Genetic analysis and fine mapping of genes controlling leaf rolling were conducted using two backcrossed generations （BC4F2, BC4F3） derived from a cross between QMX, a non-rolled leaf cultivar as a recurrent parent, and JZB, a rolled leaf NIL of ZB as a donor parent. Results indicated that leaf rolling was mainly controlled by an incompletely recessive major gene, namely rl（t）, and at the same time, affected by quantitative trait loci （QTLs） and/or the environment. A genetic linkage map was constructed using MAPMAKER/EXP3.0 with eight polymorphic markers on chromosome 2, which were screened by BAS method from 500 SSR markers and 15 newly developed insertion/deletion （InDel） markers. The position of rl（t） was estimated with composite interval mapping （CIM） method using WinQTLcart2.5. Gene rl（t） was mapped between markers InDel 112 and RM3763, and 1.0 cM away from InDel 112 using 241 plants in BC4F2 population. To fine map r（t）, one BC4F3 line with 855 plants was generated from one semi-rolled leaf plant in BC4F2. Four new polymorphic InDel markers were developed, including InDel 112.6 and InDel 113 located between markers InDe1112 and RM3763. Based on the information of recombination offered by 191 rolled leaf plants and 185 non-rolled leaf plants from the BC4F3 line ,we mapped r（t） to a 137-kb region between markers InDel 112.6 and InDel 113. Homologous gene analysis suggested that r（t）was probably related to the process of leaf development regulated by microRNA.     

Mapping and characterization of a tiller-spreading mutant<Emphasis Type="Italic">lazy-2</Emphasis> in rice

Tiller angle of rice is an important agronomic trait that contributes to breed new varieties with ideal architecture. In this study, we report mapping and characterization of a rice mutant defective in tiller angle. At the seedling stage, the newly developed tillers of the mutant plants grow with a large angle that leads to a “lazy“ phenotype at the mature stage. Genetic analysis indicates that this tillerspreading phenotype is controlled by one recessive gene that is allelic to a reported mutant la. Therefore, the mutant was named la-2 and la renamed la-1. To map and clone LA, we constructed a large mapping population. Genetic linkage analysis showed that the LA gene is located between 2 SSR markers RM202 and RM229. By using the 6 newly-developed molecular markers, the LA gene was placed within a 0.4 cM interval on chromosome 11, allowing us to clone LA and study the mechanism that controls rice tiller angle at the molecular level.