植物表皮毛发育控制基因GL2遗传互作因子的筛选和鉴定

表皮毛广泛存在于陆生植物的地上部分,是植物与环境之间的一道天然屏障,具有多种重要的生物学功能。拟南芥HD-Zip家族转录因子GLABRA 2(GL2)是调控表皮毛形成和发育的关键因子,通过筛选和鉴定GL2的遗传互作因子,可以为进一步研究植物表皮毛发育调控的分子机制奠定基础。通过大规模的遗传筛选和图位克隆,获得了一个叶片上完全没有表皮毛的突变体M12-01,遗传分析表明M12-01 single突变表型受隐性单核基因控制。M12-01 single突变体表型与拟南芥TRANSPARENT TESTA GLABKA 1(TTG1)基因的功能缺失突变体表型相似。对TTG1基因的测序结果显示其+445位碱基由鸟嘌呤突变为腺嘌呤,从而使编码的甘氨酸变为精氨酸。本研究证实TTG1突变能增强gl2-3突变体的表型,GL2基因与TTG1基因之间存在遗传互作,这为进一步研究GL2调控植物表皮毛发育的分子机制提供了新的遗传材料。     

植物表皮毛发育的分子遗传控制

植物表皮毛是一种特化的单细胞表皮结构。近年来,通过对拟南芥表皮毛的分子遗传研究已发现了多个直接控制表皮毛发育的基因,它们都编码转录因子,包括M^1YB类转录因子(GLABROUS1、WEREWOLF、TRIPTY-CHON、CAPRICE),含WD40重复序列的转录因子(TRANSPARENT TESTA GLABRA1),bHLH类转录因子(GLABROUS3)。含HD—ZIP的转录因子(GLABROUS2),WRKY类转录因子(TRANSPARENT TESTA GLABRA2)。进一步的实验证明GL1／WER—GL3—TTG1通过形成一个转录调控复合体来控制表皮毛和根毛的发育。在根毛和表皮毛的发育过程中,临近的细胞竞争表达这些转录因子决定原初细胞的命运(包括GL1／WER,GL3,TTG1,GL2),同时,还表达一些转录因子阻止临近细胞接受这个命运(包括TRY和CPC)。此外,这一复合体还是其他器官(如种皮、下胚轴气孔等)发育所共用的一种调控机制。     

植物不同类型表皮毛调控模型研究进展

表皮毛是植物地上部分表皮细胞向外突出延伸的特化毛状结构,不仅可以保护植物免受病虫的危害,还具有一定的经济和药用价值,对其调控的分子机制的阐明有利于植物的分子设计育种和遗传改良。近年来,模式植物拟南芥表皮毛形成的调控模式基本被阐明,其他植物表皮毛的调控机制也取得很大进展。鉴于此,文中综述了拟南芥和棉花(单细胞表皮毛)及番茄和青蒿(多细胞表皮毛)在基因和激素水平上对表皮毛的发育调控,同时简要介绍了其他典型单、双子叶植物表皮毛相关的研究进展,最后,展望了植物表皮毛的研究方向和应用前景。     

利用荧光标记高通量鉴定减数分裂重组抑制突变体

正向遗传学突变体筛选被广泛用于揭示减数分裂中涉及的遗传基因, 如调控减数分裂II型交叉形成途径的重组抑制基因。该研究利用拟南芥(Arabidopsis thaliana)花粉荧光标记系进行EMS突变体的正向遗传学筛选, 鉴定拟南芥野生型Col遗传背景下的重组抑制突变体, 共获得18个重组率显著提高3倍以上的重组抑制突变体, 其中包括显性和隐性遗传突变。研究表明, 基于荧光标记高通量鉴定重组抑制突变体是可行的, 可为植物减数分裂重组调控分子机制研究提供新方法和突变材料。     

利用荧光标记高通量鉴定减数分裂重组抑制突变体

正向遗传学突变体筛选被广泛用于揭示减数分裂中涉及的遗传基因, 如调控减数分裂II型交叉形成途径的重组抑制基因。该研究利用拟南芥(Arabidopsis thaliana)花粉荧光标记系进行EMS突变体的正向遗传学筛选, 鉴定拟南芥野生型Col遗传背景下的重组抑制突变体, 共获得18个重组率显著提高3倍以上的重组抑制突变体, 其中包括显性和隐性遗传突变。研究表明, 基于荧光标记高通量鉴定重组抑制突变体是可行的, 可为植物减数分裂重组调控分子机制研究提供新方法和突变材料。     

拟南芥表皮毛发育突变体abt3-1的基因定位及表型分析

在发掘和鉴定调控植物表皮毛发育的新因子过程中,获得了一个表皮毛发育异常的拟南芥隐性突变体abt3-1(aberrantly branched trichome 3-1)。与野生型拟南芥(Col-0)相比,其表皮毛分支数目明显增加。另外,abt3-1还表现出植株小、叶形宽、叶色发灰、主根短等发育缺陷。利用图位克隆技术将该突变基因ABT3定位在1号染色体上,分子标记在F28G11#3与F4N21#1之间,物理距离为134kb。该研究将为进一步克隆ABT3基因及研究其在调控植物生长发育过程中的作用奠定基础。     

蒺藜苜蓿株高控制基因COSTIN的克隆及功能研究

株高是影响植物株型建成的重要农艺性状之一,直接决定作物的倒伏性和生物产量,但目前关于苜蓿等豆科牧草株高性状形成的分子调控机制尚不清楚。通过定向筛选豆科模式植物蒺藜苜蓿Tnt1逆转座子插入突变体库,分离鉴定了一个蒺藜苜蓿矮化突变体compact stalk internodes(costin),该突变体的矮化表型是由于茎节伸长受到抑制所致。通过基因表型连锁分析成功克隆了COSTIN基因,该基因编码一个钙离子交换蛋白,与拟南芥的CALCIUM EXCHANGER 7(CAX7) 基因高度同源。qRT-PCR检测发现COSTIN基因在茎、叶和果荚等组织中有较高的表达。进一步研究发现在costin突变体中赤霉素合成途径关键基因MtCPS、MtKAO1、MtGA20ox4、MtGA20ox7和MtGA3ox1表达下调;外施赤霉素GA3可以恢复costin突变体的矮化表型。上述研究表明COSTIN基因通过影响植物激素赤霉素的生物合成来调控蒺藜苜蓿的茎节伸长。     

拟南芥与大豆疫霉菌的非寄主互作及一个感病突变体的遗传分析

非寄主抗病性是一种普遍的自然现象,该文通过建立拟南芥．大豆疫霉菌（Arabidopsis thaliana—Phytophthora sojae）非寄主互作系统,筛选对大豆疫霉菌感病的拟南芥突变体,为研究植物对卵菌的非寄主抗病性遗传机制奠定基础。以大豆疫霉菌游动孢子接种拟南芥T—DNA插入突变体离体叶片,从代表12000个独立转化株系的40000株T3代T。DNA插入拟南芥突变体中获得一系列对大豆疫霉菌感病的突变体。其中突变体581-51感病性状表现稳定,离体叶片接菌后3天内出现明显的水渍状病斑,4—5天后产生大量卵孢子和／或孢子囊。细胞学观察发现有典型的吸器形成。Southern杂交和遗传分析结果表明,581—51突变体含有4个T-DNA插入事件,其感病性状可能由隐性单基因控制。     

拟南芥与大豆疫霉菌的非寄主互作及一个感病突变体的遗传分析

非寄主抗病性是一种普遍的自然现象, 该文通过建立拟南芥-大豆疫霉菌(Arabidopsis thaliana-Phytophthora sojae)非寄主互作系统, 筛选对大豆疫霉菌感病的拟南芥突变体, 为研究植物对卵菌的非寄主抗病性遗传机制奠定基础。以大豆疫霉菌游动孢子接种拟南芥T-DNA插入突变体离体叶片, 从代表12 000个独立转化株系的40 000株T₃代T-DNA插入拟南芥突变体中获得一系列对大豆疫霉菌感病的突变体。其中突变体581-51感病性状表现稳定, 离体叶片接菌后3天内出现明显的水渍状病斑, 4–5天后产生大量卵孢子和/或孢子囊。细胞学观察发现有典型的吸器形成。Southern杂交和遗传分析结果表明, 581-51突变体含有4个T-DNA插入事件, 其感病性状可能由隐性单基因控制。     

拟南芥YUAN1基因调控器官形状和大小

器官形状和大小的控制是一个基本的发育生物学过程, 受细胞分裂和细胞扩展的影响。到目前为止, 人们对植物器官形状和大小的调控机制知之甚少。本实验室前期研究发现了一个种子和器官大小的调控基因DA1, 其编码一个泛素受体。在拟南芥(Arabidopsis thaliana)中, DA1通过抑制细胞的分裂来限制种子和器官的大小。本研究通过激活标签的方法在da1-1突变体背景下筛选到一个叶子形状发生改变的半显性突变体(yuan1-1D)。yuan1-1D形成短而圆的叶片和短的叶柄, 细胞学分析显示, 叶片和叶柄变短的主要原因是细胞的长向扩展降低导致的。YUAN1编码一个含有PHD锌指结构域的蛋白。GFP-YUAN1融合蛋白定位在细胞核内。过量表达YUAN1基因导致叶片和叶柄变短。遗传学分析显示, YUAN1和DA1、ROT3以及ROT4在控制叶片形状和大小方面作用于不同的遗传途径中。因此, 本研究鉴定了一个新的控制器官形状和大小的基因YUAN1, 为阐明植物器官形状和大小调控的分子机制提供了重要线索。     

Genetic control of trichome branch number in Arabidopsis: the roles of the FURCA loci

We are using trichome (hair) morphogenesis as a model to study how plant cell shape is controlled. During a screen for new mutations that affect trichome branch initiation in Arabidopsis, we identified seven new mutants that show a reduction in trichome branch number from three branches to two. These mutations were named furca, after the Latin word for two-pronged fork. These seven recessive mutations were placed into four complementation groups that define four new genes: FURCA1, FURCA2, FURCA3 and FURCA4. The trichome branch number phenotype indicates that the FURCA genes encode positive regulators of trichome branch initiation. Analysis of double mutants suggests that primary and secondary branch initiation events are not genetically distinct, but rely on the levels of partially redundant groups of regulators of trichome branch initiation. Based on the analysis of both epistatic and additive genetic interactions between the FURCA genes and other genes that control trichome branch number, we propose a model that explains how these genes interact to control trichome branch initiation. This model successfully predicts the phenotypes of all the single and double mutants examined and suggests points of control of the trichome branch pathway.     

Zinc finger protein5 is required for the control of trichome initiation by acting upstream of zinc finger protein8 in Arabidopsis

Arabidopsis (Arabidopsis thaliana) trichome development is a model system for studying cell development, cell differentiation, and the cell cycle. Our previous studies have shown that the GLABROUS INFLORESCENCE STEMS (GIS) family genes, GIS, GIS2, and ZINC FINGER PROTEIN8 (ZFP8), control shoot maturation and epidermal cell fate by integrating gibberellins (GAs) and cytokinin signaling in Arabidopsis. Here, we show that a new C2H2 zinc finger protein, ZFP5, plays an important role in controlling trichome cell development through GA signaling. Overexpression of ZFP5 results in the formation of ectopic trichomes on carpels and other inflorescence organs. zfp5 loss-of-function mutants exhibit a reduced number of trichomes on sepals, cauline leaves, paraclades, and main inflorescence stems in comparison with wild-type plants. More importantly, it is found that ZFP5 mediates the regulation of trichome initiation by GAs. These results are consistent with ZFP5 expression patterns and the regional influence of GA on trichome initiation. The molecular analyses suggest that ZFP5 functions upstream of GIS, GIS2, ZFP8, and the key trichome initiation regulators GLABROUS1 (GL1) and GL3. Using a steroid-inducible activation of ZFP5 and chromatin immunoprecipitation experiments, we further demonstrate that ZFP8 is the direct target of ZFP5 in controlling epidermal cell differentiation.     

Roles of the GLABROUS1 and TRANSPARENT TESTA GLABRA Genes in Arabidopsis Trichome Development

Arabidopsis trichomes are branched, single-celled epidermal hairs. These specialized cells provide a convenient model for investigating the specification of cell fate in plants. Two key genes regulating the initiation of trichome development are GLABROUS1 (GL1) and TRANSPARENT TESTA GLABRA (TTG). GL1 is a member of the myb gene family. The maize R gene, which can functionally complement the Arabidopsis ttg mutation, encodes a basic helix-loop-helix protein. We used constitutively expressed copies of the GL1 and R genes to test hypotheses about the roles of GL1 and TTG in trichome development. The results support the hypothesis that TTG and GL1 cooperate at the same point in the trichome developmental pathway. Furthermore, the constitutive expression of both GL1 and R in the same plant caused trichomes to develop on all shoot epidermal surfaces. Results were also obtained indicating that TTG plays an additional role in inhibiting neighboring cells from becoming trichomes.     

Epidermal differentiation: trichomes in Arabidopsis as a model system

Arabidopsis trichomes are an excellent model system to study all aspects of cell differentiation including cell fate determination, cell cycle regulation, cell polarity and cell expansion. Genetic analysis had initially identified mutants affecting trichome development at different developmental stages. During recent years, molecular analysis of the corresponding genes has revealed a first glimpse of the underlying molecular mechanisms. This paper summarizes some of the recent insights regarding the mechanisms of trichome development.