Arabidopsis (Brassicaceae) flower development and gynoecium patterning in wild type and Ettin mutants

Screening for mutations that alter flower development in Arabidopsis has led to the identification of two general types of genetic loci: those affecting meristem and organ identity, and those affecting growth and development independent of identity. ettin (ett) mutants belong to the latter class and exhibit pleiotropic phenotypes distinct from previously described Arabidopsis mutants. These phenotypes include increases in sepal and petal number, decreases in stamen number and anther locule number, and gross alteration of tissue patterning in the gynoecium. To determine when and how differences in ett floral meristems originate, flower development was compared between the wild type and ett mutants. ett floral meristems exhibit increases in abaxial sepal and petal primordia number without apparent increases in meristem size. Extra sepal and petal primordia develop into normal organs. In contrast, stamen and carpel primordia exhibit alterations in shape and form, subsequent to premature elongation of the terminal floral meristem. Phenotypes are allele-strength dependent. The stigma develops precociously and style differentiation is basally and abaxially misplaced in ett gynoecia. The data are discussed in the context of a model suggesting that two concentric boundaries specify the apical-basal pattern of gynoecium differentiation.     

RNA干涉AtSUS3影响拟南芥SUS家族表达模式及角果成熟

蔗糖合成酶（SuSy）是植物蔗糖代谢的关键酶,在植物生长发育过程中起着重要作用.为研究拟南芥中SUS3的功能,构建RNAi-SUS3干涉载体,通过农杆菌介导的真空渗透法转化拟南芥.筛选获得纯系转基因植株后,对AtSUS家族进行表达分析,利用环境扫描电子显微镜观察转基因植株表型,并对转基因拟南芥角果进行木质素组织化学染色以及透射电子显微镜检测.结果表明,RNA干涉技术能够抑制AtSUS3的表达,正常培养条件下该基因沉默后对拟南芥的表型没有显著影响,但可引起角果中AtSUS1,AtSUS2和AtSUS4表达代偿性增加,使转基因植株角果内果皮层细胞次生细胞壁增厚,木质化程度加深,同时果瓣厚度也有增加趋势.结果提示,转基因拟南芥角果的发育较野生型植株更为优先,AtSUS3基因沉默可能有利于角果的成熟.     

蔗糖合酶基因AtSUS3干涉后对拟南芥角果发育的影响

蔗糖合酶(SuSy)是植物蔗糖代谢关键酶之一,该研究利用反向遗传学手段,采用RNAi技术抑制拟南芥中AtSUS3基因的表达,测定纯系转基因植株的抽苔率,并对酶活性、糖含量等指标以及糖代谢相关基因的表达进行了检测,探讨SuSy在植物发育中的作用。结果显示:(1)转基因拟南芥的抽苔平均早于野生型植株2～3d,且优先3～4d完成抽苔。(2)开花后生长天数对角果蔗糖和葡萄糖含量有显著影响,而对果糖含量影响不显著;开花后5d时,野生型株系的葡萄糖含量显著高于转基因株系SUS3-2,至15d时,两种转基因株系葡萄糖含量均显著低于野生型株系。(3)开花后生长天数对SuSy、SPS、INV的活性均有显著影响,随开花时间延长,野生型株系SuSy活性显著低于转基因株系,而SPS和INV则相反。(4)AtSUS3基因沉默对其他糖代谢基因有不同程度的影响,开花后5d时,转基因植株的角果中AtCesA1、AtCesA7和AtCINV1的表达量较野生型都有所增加;开花后15d时,转基因植株的角果中AtCesA1、AtCesA7的表达量较野生型高,而AtCINV、AtCwINV的表达量比野生型低。研究表明,拟南芥AtSUS3基因沉默后,在正常生长条件下未造成植株发育异常,同时还可能通过同源家族中其他SuSy的表达水平增加,促进了该酶及糖代谢相关基因整体水平的增加,有助于角果成熟。     

Characterization and genetic mapping of a mutation (ms35) which prevents anther dehiscence in Arabidopsis thaliana by affecting secondary wall thickening in the endothecium

The male sterile mutant, ms35 , of Arabidopsis thaliana was produced by X-irradiation of seeds. The mutant produces fertile pollen, but is male sterile because the anthers do not dehisce. Anther development in ms35 plants occurs as in wild-type Arabidopsis until shortly after microspores are released from meiotic tetrads. Thereafter, in the wild type, bands of lignified, cellulosic secondary wall thickenings are laid down around the cells of the anther endothecium. In contrast, wall thickenings are not formed in the endothecium of the ms35 mutant. Development of other lignified tissues, for example the vascular tissue of the stamen, occurs normally in ms35 plants. In mutant anthers, as pollen maturation is completed, the stomium is cleaved but the anther wall does not retract to release pollen. The block in anther dehiscence in ms35 plants is specifically correlated with the absence of endothecial wall thickenings. The ms35 mutation represents the first genetic evidence in support of the proposed role of the endothecium in anther dehiscence. The ms35 gene was mapped to the top arm of chromosome 3 ( hy2 -(4.17±2.31 cM)- ms35 -(32.14±5.45 cM)- gl1 ).     

拟南芥角果发育和开裂的调控机制及在油菜育种中的应用

十字花科芸苔属甘蓝型油菜(Brassica napus)在角果发育成熟过程中,因角果开裂种子散落引起产量损失最低达20%左右,最高可达50%左右。模式植物拟南芥在角果形态和开裂机制方面与甘蓝型油菜具有相似性,角果开裂主要与果瓣、胎座框和果瓣边缘层的细胞发育有关。通过对拟南芥角果发育期间基因对果瓣、胎座框和果瓣边缘层的识别和发育进行综述,明确了拟南芥角果发育和开裂的基因调控机制,提出了从模式植物到大田作物甘蓝型油菜抗裂角育种的新策略。