一个新的水稻小穗梗弯曲突变体的形态特征及基因定位

稻穗小穗梗的发育与产量有着密切关系。文章利用⁶⁰Co g 射线辐照籼稻品种“浙农7号”, 获得一个性状能稳定遗传的小穗梗弯曲突变体bpb1 (bent pedicel branch 1), 表现为小穗梗弯曲, 并伴有小穗梗长度增长、穗长缩短和植株矮化等特点。扫描电镜观察显示, bpb1突变体小穗梗的表皮毛及气孔变小, 外表皮细胞和厚壁细胞排列不规则, 接近弯曲部位的细胞变小、排列更为紧密。bpb1突变体小穗梗横切面观察表明, 小维管束排列结构发生明显变化。遗传分析表明该突变表型受隐性单基因控制。利用bpb1突变体与粳稻品种“浙农大104”杂交构建的F₂群体进行基因定位, 将bpb1基因定位于水稻第7号染色体长臂SSR标记RM21537和RM21552之间, 该区间的物理距离为343 kb, 该区域内未发现与水稻小穗梗发育相关的已知基因。文章为bpb1基因的克隆和功能研究奠定了重要基础。     

水稻穗型的遗传调控研究进展

穗型作为水稻(Oryza sativa)重要的农艺性状,近年来一直是研究热点。该文简要介绍了水稻穗部发育的一般过程,总结了近年来发现的调控水稻穗型相关基因,并根据水稻幼穗发育过程将其分为4类:分别调控枝梗分生组织的形成、枝梗分生组织的大小、小穗分生组织的转变时间以及枝梗的伸长;并概括分析了上述基因在调控水稻幼穗发育过程中所呈现出的路径关系。最后对水稻穗型遗传调控研究的未来发展方向进行了展望。     

一个水稻畸形颖壳突变体ah的鉴定及其突变性状的遗传分析

水稻畸形颖壳突变体ah是双胚苗品系W2555中自然突变产生的。该突变体的内外稃畸形,退化;雄蕊雌蕊化,雌蕊败育;浆片同源转化为类内外稃的结构,推测该突变体可能影响B功能基因的正常发育。与野生型相比,突变体的小穗分支稀疏,每级枝梗上颖花数目减少,一般为4～6朵;小穗顶端的颖花经常不能成熟,表现为颖花始终泛白,不能转绿,因此该突变也影响花序分生组织的发育。进一步的研究证明,该突变体的发育受外界环境的影响。突变性状的遗传分析表明,该突变体由单隐性基因控制。     

水稻散状穗突变体sp的遗传分析及基因初定位

水稻(Oryza sativa)是我国最主要的粮食作物之一, 其穗部形态直接影响着水稻产量和稻米品质。在秋光和七山占构建的重组自交系群体中发现了1个散穗突变体材料sp (spreading panicle), 田间表现为穗部一次枝梗向外延伸, 与穗轴夹角增大, 且向四周散开, 故暂命名为散穗突变体sp。与野生型相比, 突变体sp穗重、每穗粒重、千粒重、粒宽以及粒厚均极显著减少, 推测SP可能是1个参与调控穗部形态建成和颖花发育的基因。遗传分析表明, 该性状受1个显性核基因控制。利用sp与02428构建的F₂群体进行基因定位, 将该基因定位在4号染色体长臂端, 位于E3和RM17578之间的62.9 kb区域内。该结果将为SP基因的图位克隆和揭示其作用机理奠定基础。     

一份水稻矮杆小粒突变体的形态特征和基因定位

从水稻T-DNA插入突变体库中鉴定出一个矮杆小粒突变体t129,该突变体与野生型植株相比,植株明显矮化,籽粒粒长明显缩短,千粒重下降。遗传分析表明,t129的突变性状由一对隐性核基因控制,该基因(T129)经图位克隆定位于水稻第5染色体长臂上,引物InDel43和InDel57之间,物理距离为430 kb,并与标记InDel51共分离。本研究明确了该矮杆小粒突变体的表型特征及遗传规律,为进一步研究调控水稻株高和粒型基因奠定基础。     

水稻突变体des2和des5的研究和定位

小穗发育是决定水稻产量的主要农艺性状,鉴定控制小穗发育的关键基因对研究和分析调控农艺性状的分子机理是至关重要的.本文中,我们鉴定了一组小穗数目明显减少的突变体,命名为decteased spikelets(des),这里详细研究des2和des5两个突变体.结果显示des2是由单基因隐性位点控制,图位克隆将此位点定位到6号染色体的长臂上,并最终克隆了此基因,发现des2是moc1的一个新的等位突变体.定位克隆和序列分析显示在des5中,LAX基因的编码HLH(螺旋一环一螺旋)结构域的区域发生了一个点突变,暗示des5是lax的一个新的等位突变体.我们的结果暗示小穗和水稻叶腋分枝的发育受相同的遗传途径调控.     

水稻穗顶部退化基因PAA2的精细定位

鉴定和克隆水稻穗顶部退化突变体新基因,对研究小穗顶部退化的分子机制及克服育种和生产实践中因穗顶部退化引起的产量损失具有重要的理论和现实意义。本研究报道了一个来源于中花11的穗顶部退化突变体,暂命名为Panicle Apical Abortion 2(paa2)。该突变体的穗顶部小穗发育异常、退化,后期退化部分脱落,稻穗形成秃尖,使穗粒数减少。遗传分析表明该突变体受1个显性基因控制。利用群体分离分析法(BSA,bulked segregation analysis)将PAA2基因定位在2号染色体的长臂端L2-33和L2-50之间,物理距离为80 kb的范围内。该研究结果为PAA2基因的图位克隆奠定了基础。     

直立密穗基因DEP2-1388的遗传分析及在杂交稻中的育种利用

通过EMS诱变籼型重穗恢复系蜀恢498,获得一个直立穗突变体R1338。与野生型相比,突变体表现为植株变矮、穗直立、穗长变短、一次枝梗变短、着粒密度增加、穗部抗弯曲力极显著增强、籽粒增宽增厚、粒长变短。组织细胞学分析发现,穗颈节直径、纤维素含量和木质素含量在穗部抗弯曲上发挥了重要的作用。遗传分析表明该直立穗表型受一对半显性核基因DEP2控制,通过重测序以及MutMap方法定位发现,在R1338突变体中,DEP2第7外显子有一个A到G的碱基置换,导致第928个精氨酸(AGG)被置换成甘氨酸(GGG),推测R1338直立穗性状可能由DEP2中该SNP导致。用R1338、野生型与不同穗型不育系分别配组,R1338与弯曲穗不育系所配组合穗部表现半直立,且保持较高的结实率和杂种优势,与DEP1直立穗不育系配组表现为基因累加效应的直立穗。本研究还讨论了直立穗突变体R1338在杂交水稻育种中的利用价值。     

一个水稻矮秆突变体的遗传分析及基因定位

水稻（Oryza sativa）是我国重要的粮食作物之一。水稻矮秆材料的引入掀起了第1次＂绿色革命＂。但近年来,在水稻育种中矮生基因遗传单一的问题越来越突出,已经严重影响到水稻产量的持续提高。利用60Co-γ射线辐照籼稻亲本材料M804获得了一个性状能够稳定遗传的矮秆突变体MU101。对该矮秆突变体和台粳16号杂交获得的F2代的遗传分析表明,该矮秆性状受1对隐性单基因控制,并暂命名为ds1。利用已有的SSR分子标记将DS1基因定位在水稻第5号染色体上,通过扩大群体和开发新的Indel标记,进一步将DS1基因定位在2个Indel标记之间,两者间的物理距离大约为384kb。该研究为DS1基因的克隆及其在生产中的应用奠定了基础。     

水稻无内稃突变体的遗传分析和基因定位

花器官发育异常的突变体是研究植物花发育分子遗传机制的良好实验材料,以水稻无内稃突变体为父本,生47、N625和CDR22为母本配制杂交组合进行性状遗传分析,根据F2代表型及X^2测验结果表明,突变性状是由单隐性基因控制的,选用突变体为父本,生47为母本杂交的F2群体作定位群体,利用SSLP标记的和RFLP标记将与突变性状相关的基因定位在第6染色体短臂上RFLP标记C498和RZ450之间,暂定名为npa-1。为进一步的基因克隆及功能研究奠定了基础。     

水稻小穗特征基因FZP的图位克隆

FZP是水稻中控制小穗分化的一个关键基因,先前已将它定位在第7染色体上。通过进一步对该基因进行精细定位和图位克隆,找到2个SSR标记NRM6和NRM8,将该基因锁定在一个遗传距离为1．2cM的范围内(两标记与目标基因的遗传距离分别为0．2cM和1．0cM),相应的物理距离为144kb。发现在预期的目标基因位置,存在一个具有类似AP2结构域的基因。已知AP2是一个控制植物花发育的重要基因。因此,这个基因应是FZP的一个候选基因。PCR扩增结果显示,突变体中该基因有一个大约4kb的插人片段,与向共分离。由此可以初步认为,该基因就是FZP。     

籼型常规早稻穗分化期低温对颖花形成和籽粒充实的影响

以籼型常规早稻中嘉早17为材料,于盆栽条件下采用人工气候箱控温,在水稻穗分化一次枝梗原基分化期(Ⅱ)与花粉母细胞减数分裂期(Ⅵ)进行17和20 ℃的低温胁迫处理,研究不同低温对水稻枝梗、颖花分化与退化及籽粒充实的影响.结果表明： 与对照相比,不同低温处理均显著降低每穗枝梗及颖花分化数和现存数,颖花现存数降幅为7.2%～12.4%,同时增加了枝梗和颖花的退化数,影响了花粉活性、花药开裂等花器官发育,导致籽粒充实不良,以17 ℃低温胁迫效应更明显.穗分化Ⅵ期低温处理总枝梗和颖花分化数与现存数低于穗分化Ⅱ期,但二次枝梗和颖花退化数较多,颖花退化数较穗分化Ⅱ期高11.6%;穗分化Ⅱ期低温处理穗部籽粒结实率显著低于穗分化Ⅵ期,降幅达3.7%,主要与花粉粒活性、柱头花粉散落数、花药开裂系数和籽粒充实度受低温影响较大有关.另外,穗分化Ⅱ、Ⅵ两时期受17 ℃低温胁迫效应大于20 ℃.综合穗分化两时期低温胁迫效应的差异,生产中需加强相应栽培措施的调控.     

开放式空气CO2浓度增高对水稻颖花分化和退化的影响

在大田栽培条件下 ,研究开放式空气CO2 浓度增加 (FACE) 2 0 0 μmol·mol-1的处理对水稻每穗 1、2次枝梗及其颖花的分化数、退化数、现存数及退化率的影响 .结果表明 ,FACE处理对每穗 1、2次枝梗的分化数及 1次枝梗的退化数、退化率均无显著影响 ,但使 2次枝梗的退化数、退化率显著提高 ,使 2次枝梗现存数明显减少 ;FACE处理对每穗 1、2次颖花的分化数和 1次颖花的退化数、现存数、退化率均无显著影响 ,但使每穗 2次颖花的退化数和退化率显著提高 ;FACE处理使每穗颖花现存数显著减少主要是因为FACE处理使现存 1次枝梗上 2次枝梗大量退化引起 2次颖花退化所致 ;FACE处理使 1次颖花现存数占全穗的比率显著增加 ,使 2次颖花现存数占全穗的比率显著降低 .     

开放式空气CO2浓度增高对水稻颖花分化和退化的影响

在大田栽培条件下,研究开放式空气CO₂浓度增加(FACE)200μmol·mol^-1的处理对水稻每穗1、2次枝梗及其颖花的分化数、退化数、现存数及退化率的影响.结果表明,FACE处理对每穗1、2次枝梗的分化数及1次枝梗的退化数、退化率均无显著影响,但使2次枝梗的退化数、退化率显著提高,使2次枝梗现存数明显减少;FACE处理对每穗1、2次颖花的分化数和1次颖花的退化数、现存数、退化率均无显著影响,但使每穗2次颖花的退化数和退化率显著提高;FACE处理使每穗颖花现存数显著减少主要是因为FACE处理使现存1次枝梗上2次枝梗大量退化引起2次颖花退化所致;FACE处理使1次颖花现存数占全穗的比率显著增加,使2次颖花现存数占全穗的比率显著降低.     

Morphological and molecular characterization of a new frizzy panicle mutant, "fzp-9(t)", in rice (Oryza sativa L.)

The spikelet identity gene "fzp" (frizzy panicle) is required for transformation of the floral meristems to inflorescent shoots. In fzp mutants, spikelets are replaced by branches and spikelet meristems produce massive numbers of branch meristems. We have isolated and characterized a new fzp mutant derived from anther culture lines in rice and designated as fzp-9(t). The fzp-9(t) mutant showed retarded growth habit and developed fewer tillers than those of the wild-type plant. The primary and secondary rachis branches of fzp-9(t) appeared to be normal, but higher-order branches formed continuous bract-like structures without developing spikelets. The genetic segregation of fzp-9(t) showed a good fit to the expected ratio of 3: 1. The sequence analysis of fzp-9(t) revealed that there is a single nucleotide base change upstream of the ERF (ethylene-responsive element-binding factor) domain compare to wild-type plant. The mutation point of fzp-9(t) (W66G) was one of the six amino acids of the ERF domain that contributed to GCC box-specific binding. The premature formation of a stop codon at the beginning of the ERF domain might cause a non-functional product.     

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.     

Morphological characteristics and gene mapping of a dense panicle (dp2) mutant in rice (Oryza sativa L.)

A dense panicle mutant (dp2) derived from the Oryza sativa ssp. japonica cultivar Nipponbare through ethyl methane sulfonate mutagenesis was used in present study. Compared to the wild type, the panicle of dp2 mutant exhibited more branches and denser grains. Further more, the number of spikelets per panicle, number of primary branches and secondary branches of dp2 mutant were significantly increased while the panicle length, and 1,000-grain weight were significantly decreased. The results from the genetic analysis indicated that the dense panicle phenotype was controlled by a single dominance nuclear gene. Polymorphic analysis of SSR and InDel markers demonstrated that the DP2 gene was located at the long arm of chromosome 2, which was further mapped between SSR markers RM341 and RM13356 in a physical region of 398 kb. Within this region, the RCN2 (LOC_Os02g32950) gene which was annotated relating to the development of rice panicle was found. Compared to the wild type, the sequence of RCN2 gene in the dp2 mutant showed that two SNPs replacement had taken place in the promoter region (G–A) and the intron region (A–T), respectively. The dp2 mutant could be a novel mutant of RCN2 gene and this novel mutant might be useful for further studies on this 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…     

Reexamination of silicon effects on rice growth and production under field conditions using a low silicon mutant

Silicon (Si) is a beneficial element for healthy growth and high and sustainable production of rice, but the mode of action of the beneficial effects has not been well understood. We carried out field trials for four years at two different locations to re-examine the effects of Si on the growth and production of rice using a low silicon rice (lsi1) mutant. The mutant accumulated much lower Si at each growth stage compared with the wild-type rice (Oryza sativa L. cv Oochikara), but there was no difference in the accumulation of other nutrients including N, P, and K. Measurements at different growth stages showed that low Si in the mutant hardly affected the tiller number, chlorophyll content (SPAD value), and root growth. The plant height and shoot dry weight of the wild-type rice were slightly higher than those of the mutant at a later growth stage, but the difference was not significant between the two lines. However, grain yield was reduced by 79–98%, depending on year, due to a low Si accumulation in the mutant, which showed the largest effect of Si on rice production among all studies reported so far. Among the yield components, the percentage of filled spikelets was mostly affected, being only 13.9% of the wild-type rice in the mutant. The grain color of the mutant became brown because of excessive transpiration and infection of pathogens. These results indicate that Si increases rice yield mainly by enhancing the fertility of spikelets.     

转拟南芥NPR1基因桂99 T3代植株的抗病性及农艺性状表现

以转拟南芥AtNPR1基因的恢复系品种桂99T3代纯合株系为材料,考查其农艺性状及其抗病性,并比较转基因植株与桂99侵染水稻白叶枯病菌后的农艺性状。结果表明:转基因植株表现出对水稻白叶枯病的抗性显著增强77%以上;穗长、剑叶长、有效穗数、一次枝梗数、每穗实粒数、单株产量和谷粒宽等农艺性状与未转基因桂99无显著差别。在受到水稻白叶枯病菌侵染后,转基因植株的一次枝梗数、每穗粒数、每穗实粒数和单株产量等方面均比对照桂99高出13%～78%。说明AtNPR1基因增强了水稻的抗病能力,从而降低了病害引起的产量损失。转基因植株的恢复力不受影响,稻米品质比桂99更加优良。本工作为转基因水稻抗病育种的研究奠定了基础。