Fine mapping of a pistilloid-stamen (PS) gene on the short arm of chromosome 1 in rice.

A novel floral organ mutant of rice (Oryza sativa L. subsp. indica), termed pistilloid-stamen (ps) here, has flowers with degenerated lemma and palea, with some stamens transformed into pistils and pistil-stamen chimeras. Genetic analysis confirmed that the ps trait is controlled by a single recessive gene. F2 and F3 segregation populations derived from PS ps heterozygote crossed with Oryza sativa subsp. indica 'Luhui-17' (PS PS) were used for molecular mapping of the gene using simple sequence repeat (SSR) markers. With 97 recessive individuals from an F2 segregation population, the ps locus was preliminarily mapped 6.2 cM distal to marker RM6324 and 3.1 cM proximal to marker RM6340 in the terminal region of the short arm of chromosome 1. With a large F3 segregation population, the gene was fine-mapped between markers RM6470 and RM1141, at distances of 0.10 and 0.03 cM to each marker, respectively. The position of the ps gene was finally located within a 20 kb physical region containing 3 annotated putative genes. One of them, encoding a protein with a single C2H2 zinc-finger domain, may be the candidate gene for PS.     

水稻(Oryza sativa L.)苗期低温白化突变体al12的超微结构与基因定位

水稻苗期低温白化突变是水稻在发育早期对低温胁迫的一种适应性,是一种受发育和温度控制的条件表达,它与其他水稻白化突变有本质的不同.本研究利用便携式叶绿素测量仪测定了白化时期植株的叶绿素含量和用透射电镜观察了叶绿体的结构变化.结果发现叶绿素平均含量仅为1.2(SPAD),而叶绿体也不能正常发育仅有囊泡状结构.通过与9311的正反交实验及子代的分离表现证明该性状受一个隐性核基因的控制.另外利用SSR分子标记技术将该基因定位在第8染色体上,两侧最近的SSR标记RM5068和RM3702分别距基因0.5～1.1 cM和4.9 cM,基因被定位在约6个cM的区间内.我们将该基因暂时命名为al12.     

Disruption of a guard cell-expressed protein phosphatase 2A regulatory subunit,RCN1, confers abscisic acid insensitivity in Arabidopsis

Pharmacological studies have led to a model in which the phytohormone abscisic acid (ABA) may be positively transduced via protein phosphatases of the type 1 (PP1) or type 2A (PP2A) families. However, pharmacological evidence also exists that PP1s or PP2As may function as negative regulators of ABA signaling. Furthermore, recessive disruption mutants in protein phosphatases that function in ABA signal transduction have not yet been identified. A guard cell-expressed PP2A gene, RCN1, which had been characterized previously as a molecular component affecting auxin transport and gravity response, was isolated. A T-DNA disruption mutation in RCN1 confers recessive ABA insensitivity to Arabidopsis. The rcn1 mutation impairs ABA-induced stomatal closing and ABA activation of slow anion channels. Calcium imaging analyses show a reduced sensitivity of ABA-induced cytosolic calcium increases in rcn1, whereas mechanisms downstream of cytosolic calcium increases show wild-type responses, suggesting that RCN1 functions in ABA signal transduction upstream of cytosolic Ca(2+) increases. Furthermore, rcn1 shows ABA insensitivity in ABA inhibition of seed germination and ABA-induced gene expression. The PP1 and PP2A inhibitor okadaic acid phenocopies the rcn1 phenotype in wild-type plants both in ABA-induced cytosolic calcium increases and in seed germination, and the wild-type RCN1 genomic DNA complements rcn1 phenotypes. These data show that RCN1 functions as a general positive transducer of early ABA signaling.     

Disparate roles for the regulatory A subunit isoforms in Arabidopsis protein phosphatase 2A

The heterotrimeric protein phosphatase 2A (PP2A) complex comprises a catalytic subunit and regulatory A and B subunits that modulate enzyme activity and mediate interactions with other proteins. We report here the results of a systematic analysis of the Arabidopsis (Arabidopsis thaliana) regulatory A subunit gene family, which includes the ROOTS CURL IN NAPHTHYLPHTHALAMIC ACID1 (RCN1), PP2AA2, and PP2AA3 genes. All three A subunit isoforms accumulate in the organs of seedlings and adult plants, suggesting extensive overlap in expression domains. We have isolated pp2aa2 and pp2aa3 mutants and found that their phenotypes are largely normal and do not resemble that of rcn1. Whereas rcn1 pp2aa2 and rcn1 pp2aa3 double mutants exhibit striking abnormalities in all stages of development, the pp2aa2 pp2aa3 double mutant shows only modest defects. Together, these data suggest that RCN1 performs a cardinal role in regulation of phosphatase activity and that PP2AA2 and PP2AA3 functions are unmasked only when RCN1 is absent.     

小粒野生稻导入系对稻飞虱的抗性鉴定与分析

稻飞虱是水稻生产最严重的害虫之一。野生稻拥有丰富的抗虫基因资源,导入系是鉴定和利用野生稻有利基因的有效途径。本研究通过对371份小粒野生稻导入系进行抗褐飞虱和白背飞虱接虫鉴定,分别筛选出了11份抗、72份中抗褐飞虱的材料和7份抗、45份中抗白背飞虱的材料,其中有5份材料兼抗褐飞虱和白背飞虱,这是从小粒野生稻中鉴定出抗白背飞虱材料的首次报道。通过对2份抗性导入系材料与感虫亲本杂交构建的F1和F2群体的抗虫鉴定和分析表明:K41对褐飞虱和白背飞虱的抗性受2对显性抗虫基因通过互补作用所控制;P114对褐飞虱和白背飞虱的抗性都是由1对主效的隐性基因控制。这些结果必将有利于小粒野生稻抗稻飞虱的基因定位和育种利用。     

一份新型水稻极度分蘖突变体的遗传分析及分子标记定位

在三系杂交水稻保持系绵香1B（M1B）和一个雄性不育材料GMS-1的杂交后代中发现一株极度分蘖突变体（命名为ext．M1B）,其分蘖数为121。对ext-M1B与5个正常分蘖水稻品种杂交F1和F2代的遗传分析表明,ext-M1B的极度分蘖特性受一对隐性核基因控制。以2480B／ext-M1B的F2代作定位群体,用分子标记将ext-M1B的突变基因定位于水稻第6染色体短臂,该基因与微卫星标记RM197、RM584和RM225的遗传距离分别为3．8cM、5．1cM和5．2cM,认为ext-M1B突变基因是一个新的水稻极度分蘖基因,暂命名为ext-M1B（t）。     

Genetic interaction between 2 tillering genes, reduced culm number 1 (rcn1) and tillering dwarf gene d3, in rice

Mutant genes, reduced culm number 1 (rcn1) and bunketsuwaito tillering dwarf (d3), affect tiller number in rice (Oryza sativa L.) in opposite directions. The d3 mutant was reported to increase tiller number and reduce plant stature. Our objective was to compare the phenotype of the d3rcn1 double mutant with each single mutant and parental rice cultivar "Shiokari" and to clarify whether the Rcn1 gene interacted with the D3 gene. We recovered a new rcn1 mutant from Shiokari and developed d3rcn1 double mutant with Shiokari genetic background. A new rcn1 mutant, designated as "S-97-61" exhibited a reduction in tiller number and plant stature to about the same level as the previously reported original rcn1 mutant. Three near-isogenic lines, rcn1 mutant, d3 mutant, and d3rcn1 double mutant, were grown together with the parental Shiokari. The reduction in tillering by the rcn1 mutation was independent of the d3 genotype, and tillering number of d3rcn1 double mutant was between those of the d3 and rcn1 mutants. These results demonstrated that the Rcn1 gene was not involved in the D3-associated pathway in tillering control.     

水稻粒长基因GL3的遗传分析和分子标记定位

为了解析水稻粒长的遗传机制,以大粒水稻品种‘80018-TR161-2-1’和小粒水稻品种‘日本小黑稻’及其F2代200个株系和F2：3家系为材料,分析水稻粒长的遗传学性状。结果表明,谷粒长度的分离比在F2及F2：3家系中都表现为3：1,长粒性状受1对隐性核基因控制,命名为GL3。用简单重复序列（simple sequence repeat,ssR）分子标记结合群体分组混合分析的方法,将此种基因定位在水稻第3号染色体上SSR标记PSM379和RM16之间,它们的遗传距离分别为4．0cM和11．2cM。     

RCN1/OsABCG5, an ATP‐binding cassette (ABC) transporter,is required for hypodermal suberization of roots in rice (Oryza sativa)

Suberin is a complex polymer composed of aliphatic and phenolic compounds. It is a constituent of apoplastic plant interfaces. In many plant species, including rice (Oryza sativa), the hypodermis in the outer part of roots forms a suberized cell wall (the Casparian strip and/or suberin lamellae), which inhibits the flow of water and ions and protects against pathogens. To date, there is no genetic evidence that suberin forms an apoplastic transport barrier in the hypodermis. We discovered that a rice reduced culm number1 (rcn1) mutant could not develop roots longer than 100 mm in waterlogged soil. The mutated gene encoded an ATP‐binding cassette (ABC) transporter named RCN1/OsABCG5. RCN1/OsABCG5 gene expression in the wild type was increased in most hypodermal and some endodermal roots cells under stagnant deoxygenated conditions. A GFP‐RCN1/OsABCG5 fusion protein localized at the plasma membrane of the wild type. Under stagnant deoxygenated conditions, well suberized hypodermis developed in wild types but not in rcn1 mutants. Under stagnant deoxygenated conditions, apoplastic tracers (periodic acid and berberine) were blocked at the hypodermis in the wild type but not in rcn1, indicating that the apoplastic barrier in the mutant was impaired. The amount of the major aliphatic suberin monomers originating from C₂₈ and C₃₀ fatty acids or ω‐OH fatty acids was much lower in rcn1 than in the wild type. These findings suggest that RCN1/OsABCG5 has a role in the suberization of the hypodermis of rice roots, which contributes to formation of the apoplastic barrier.     

一个新的水稻白化转绿突变体的生理特性和基因定位

秋丰M来源于粳稻秋丰的自然白化转绿突变株。其主要特征为前三叶白化带绿,第四叶及以后叶片均为淡绿色,抽穗时,秋丰M的颖壳和前三叶一样仍出现带绿的白化现象。不同生长时期对野生型和突变型水稻叶片色素含量测定的结果与田间观察结果一致,秋丰M确实存在着一个叶色显著变化的过程。主要农艺性状的比较结果表明,秋丰与秋丰M除穗颈长和千粒重达到极显著差异外,其他农艺性状均无明显差异。遗传分析发现该突变性状受一对隐性核基因控制。以209株培矮64S×秋丰M F_2的隐性突变个体为定位群体,将突变基因定位在水稻第2染色体长臂上,位于 SSR 标记RM475和RM2-22之间,其遗传距离分别为17.3 cM和2.9 cM,并将该基因命名为gra_(t)。     

水稻抗褐飞虱基因bph2的SSR定位和标记辅助选择

利用综合性状较好对褐飞虱敏感的粳稻恢复系C418为父本,以含有bph2基因的抗褐飞虱品种ASD7为母本构建了包含134个F23家系的群体,利用苗期鉴定法对F2：3家系进行抗性鉴定：用SSR标记技术,将bph2基因定位在第12染色体长臂上,标记RM7102和RM463之间,其遗传距离分别为7．6cM和7．2cM。在进行表型选择的同时,利用与bph2基因连锁的SSR标记RM7102和RM463对BC1F1和BC2F1进行了标记辅助选择,选择效率分别为89．9％和91．2％,为培育高抗褐飞虱水稻品种奠定了基础。     

Genetic analysis and mapping of gene fzp(t) controlling spikelet differentiation in rice

A mutant of spikelet differentiation in rice called frizzle panicle (fzp) was discovered in the progeny of a cross between Oryza sativa ssp. indica cv. V20B and cv. Hua1B. The mutant exhibits normal plant morphology but has apparently fewer tillers. The most striking change in fzp is that its spikelet differentiation is completely blocked, with unlimited subsequent rachis branches generated from the positions where spikelets normally develop in wild-type plants. Genetic analysis suggests that fzp is controlled by a single recessive gene, which is temporarily named fzp (t). Based on its mutant phenotype, fzp (t) represents a key gene controlling spikelet differentiation. Some F2 mutant plants derived from various genetic background appeared as the "middle type", suggesting that the action of fzp (t) is influenced by the presence of redundant, modifier or interactive genes. By using simple sequence repeat (SSR) markers and bulked segregant analysis (BSA) method, fzp (t) gene was mapped in the terminal region of the long arm of chromosome 7, with RM172 and RM248 on one side, 3.2 cM and 6.4 cM from fzp (t), and RM18 and RM234 on the other side, 23.1 cM and 26.3 cM from fzp(t), respectively. These results will facilitate the positional cloning and function studies of the gene.     

Genetic analysis and mapping of gene fzp(t) controlling spikelet differentiation in rice

Monocots and dicots have diverged for 120 million years. The floral morpha of cereals isunique and much different from that of dicot plants. Nevertheless, it has been found that most genes controlling flower development share a conserved sequence called MADS-box[1]. Therefore,it is likely that monocots and dicots could have similar basic characteristics of flower developmentbut the mechanisms of genetic regulation for flowering induction and floral differentiation might be different[2,3]. Du…     

Ultrastructure and Gene Mapping of the Albino Mutant al12 in Rice (Oryza sativa L.)

Seedling albino mutation resistant to low temperature is an adaptability of rice (Oryza sativa L.) to cold. The mutant, a conditional expression controlled by development and temperature, differs from other albino mutants. The chlorophyll content of the mutant was measured using a portable chlorophyll meter, and the ultrastructure of the chloroplast was observed using a transmission electron microscope. Chlorophyll content was 1.2 SPAD, and the chloroplast did not develop, with only small vesicle-like structures. A segregation analysis of the reciprocal crosses between the albino mutation line with the rice line 9311 demonstrated that the albino trait was controlled by a single recessive gene, which was flanked by SSR markers RM5068 and RM3702 on the short arm of chromosome 8 with a distance of 0.5-1.1 cM and 4.9 cM, respectively. This gene was mapped within a 6 cM interval region and was tentatively referred to as al12.     

Genetic analysis and molecular mapping of a novel gene for zebra mutation in rice （Oryza sativa L.）

A novel zebra mutant, zebra-15, derived from the restorer line JinhuilO （Oryza sativa L. ssp. indica） treated by EMS, displayed a distinctive zebra leaf from seedling stage to jointing stage. Its chlorophyll content decreased （55.4%） and the ratio of Chla/Chlb increased （90.2%） significantly in the yellow part of the zebra-15, compared with the wild type. Net photosynthetic rate and fluorescence kinetic parameters showed that the decrease of chlorophyll content significantly influenced the photosynthetic efficiency of the mutant. Genetic analysis of F2 segregation populations derived from the cross of XinonglA and zebra-15 indicated that the zebra leaf trait is controlled by a single recessive nuclear gene. Ninety-eight out of four hundred and eighty pairs of SSR markers showed the diversity between the XinonglA and the zebra-15, their F2 population was then used for gene mapping. Zebra-15 （Z-15） gene was primarily restricted on the short arm of chromosome 5 by 150 F2 recessive individuals, 19.6 cM from marker RM3322 and 6.0 cM from marker RM6082. Thirty-six SSR markers were newly designed in the restricted location, and the Z-15 was finally located between markers nSSR516 and nSSR502 with the physical region 258 kb by using 1,054 F2 recessive individuals.     

Genetic and physiological characterization of the OsCem mutant in rice: formation of connected embryos with multiple plumules or multiple radicles

Establishment of the apical-basal axis is a critical event in plant embryogenesis. Two functionally distinct primordia (the plumule and radicle) are meristems that originate from the lower and upper regions, respectively, of the embryo and are arranged along an apical-basal axis. One rice mutant (OsCem), which alters the embryo axis pattern to produce multiple plumules and/or radicles, was characterized. The OsCem mutant plants showed three different phenotypes: a multiple-shoot type, a heart-shaped Siamese embryo having multiple plumules and a common radicle; a multiple-root type, an upside-down Y-shaped Siamese embryo possessing multiple radicles and a common plumule; and a connected twin type, a connected Siamese twin having two sets of plumules and radicles. These diverse phenotypes demonstrated that the upper and lower regions of the embryo axis have a similar potential to complete the full spectrum of the developmental program of multiple plumules and radicles, respectively. Genetic analysis and molecular mapping based on simple sequence repeat markers has revealed that a recessive gene was involved in the control of the connected Siamese embryo formation. By using an F2 mapping population derived from a cross between the OsCem mutant and the variety 95-15, the OsCem locus was mapped primarily to the short arm of chromosome 3 of rice (Oryza sativa) at the interval between markers RM148 (6.4 cM) and RM468 (7.5 cM). Subsequently, the OsCem locus was fine mapped to the interval between markers M5 (1.6 cM) and M6 (1.0 cM).     

一个水稻显性高秆突变体的遗传分析和基因定位

从水稻(Oryza sativa L.)的两个半矮秆籼稻品种6442S-7和蜀恢881杂交F2代群体中发现一个高秆突变体D111,其株高和秆长分别比亲本蜀恢881增加63.0%和87.0%.用205个微卫星标记分析D¨1及其原始亲本6442S-7和蜀恢881之间的基因组DNA多态性,结果未发现D111具有2个原始亲本都没有的新带型,证明D1¨的确是6442S-7和蜀恢881的杂交后代发生基因突变产生的.将D111分别与蜀恢881、蜀恢527、明恢63、9311、IR68、G46B等6个半矮秆品种和高秆对照品种南京6号杂交,分析F1和F2代株高的遗传行为,结果表明D1¨的高秆性状由一对显性基因控制,且该基因与南京6号的高秆基因紧密连锁或等位.以蜀恢527/D111 F2群体为定位群体,运用微卫星标记将D111显性高秆突变基因定位于水稻第一染色体长臂,与RM212、RM302和RM472的遗传距离分别是27.7 cM、25.5 cM和6.0 cM,该基因暂命名为LC(t).认为D111是首例从半矮秆品种自然突变产生的水稻显性高秆突变体,LC(t)为首次定位的水稻显性高秆突变基因.此外,将上述基因定位结果与Causse等(1994)和Temnykh等(2000,2001)发表的水稻分子连锁图谱进行比较,发现LC(t)基因恰巧位于与水稻"绿色革命基因"sd1相同或十分相近的染色体区域,因此,还就LC(t)基因与sd1基因之间的可能关系进行了讨论.     

水稻叶状颖壳突变体Oslh的遗传分析和OsLH基因的定位

通过γ射线诱变,从粳稻品种9522的M2代中筛选出一株具有叶状颖壳的突变体,定名Oslh(1h=leafy hull).Oslh突变体的开花时间要比野生型晚15 d左右,内外稃和浆片发育成了叶片状器官.Oslh突变体与粳稻品种9522回交结果表明Oslh突变性状可能由单核基因隐性突变造成.以Oslh突变体与籼稻品种广陆矮4号杂交的F2代群体为基因定位群体,利用SSR和InDel分子标记将Oslh突变位点定位在3号染色体上的SSR标记RM5475和InDel标记GY305之间,遗传距离分别为2.5 cM和1.9 cM.这些结果为克隆OsLH基因和研究花器官发育的调控机理奠定了基础.     

Roles of RCN1, regulatory A subunit of protein phosphatase 2A, in methyl jasmonate signaling and signal crosstalk between methyl jasmonate and abscisic acid

Methyl jasmonate (MeJA) as well as abscisic acid (ABA) induces stomatal closure with their signal crosstalk. We investigated the function of a regulatory A subunit of protein phosphatase 2A, RCN1, in MeJA signaling. Both MeJA and ABA failed to induce stomatal closure in Arabidopsis rcn1 knockout mutants unlike in wild-type plants. Neither MeJA nor ABA induced reactive oxygen species (ROS) production and suppressed inward-rectifying potassium channel activities in rcn1 mutants but not in wild-type plants. These results suggest that RCN1 functions upstream of ROS production and downstream of the branch point of MeJA signaling and ABA signaling in Arabidopsis guard cells.