植物MADS盒基因研究进展

植物中的MADS盒基因是一个序列特异的调节基因家族。它编码的蛋白转录因子在植物的生长发育中起着重要的调节作用。综述了植物MADS盒基因的进化、调节机理、与花器官发育的关系以及MADS盒相关基因克隆等方面的研究进展,并论述了MADS盒基因研究的发展趋势。     

水稻基因组MADS盒DNA的克隆和分析

利用来自金鱼草Squamosa基因的MADS盒序列作为异源探针 ,从水稻基因组Cosmid文库中筛选获得了 1个含MADS盒保守序列的DNA片段(RgMADS1 ) ,对RgMADS1进行的结构及功能研究表明 :RgMADS1中含有与已报道的MADS盒基因高度同源的区段 ;水稻基因组中存在多拷贝的含MADS盒的基因族 ;将RgMADS1与 35S启动子构成嵌合基因 ,转化拟南芥 ,转基因植株表型异常 ,主要是花型结构改变、花数目减少和花着生部位异常 .由以上分析初步认为 ,RgMADS1可能是水稻MADS盒基因家族中的一员 ,它们可能参与了花形态建成和发育过程中的功能调控     

植物MADS盒基因与花器官的进化发育

已在维管植物中发现百余种MADS盒基因,此种基因家族由表达模式和功能关系密切的基因构成多种特定的亚族和DEF／GLO类（B功能）,AG类（C和D功能）等,植物花器官发生和花形态多样性的遗传机理和进化规律都可能与MADS盒基因的结构,表达以及功能进行相关。     

胚珠发育的分子基础

胚珠作为胚囊的携带者,在植物的生殖过程中起重要作用。胚珠是种子的前身,它在受精后发育成种子。近年来通过诱变已创造出一些胚珠和胚囊发育异常的突变体,如 sin1, bell, ovm2, ovm3。这几个突变体的表现型不但是珠被发育异常,而且胚囊不能形成或发育异常,最终结果是雌性不育。同时,已分别从蝶兰和矮牵牛的胚珠中分离出一批胚珠发育特异的基因,其中有关MADS Box基因在胚珠形成和发育中的作用研究得比较清楚,基因转化工作证实胚珠的分化和形成受一类新的MADS Box基因控制。     

植物MADS-box基因研究进展

植物中的MADS-box基因是一个序列特异的调节基因家族,其编码的MADS-box蛋白转录因子以二聚体化的形式通过保守的MADS结构域与特定的DNA序列结合来调控基因的表达,从而调节植物的生长发育.对植物MADS-box基因的分布、分类、结构、功能和前景作了简要的综述。     

春化作用相关基因FLC的研究进展

拟南芥春化作用相关基因FLOWERING LOCUS C（FLC）属于MADS盒基因,它编码的蛋白转录因子对开花具抑制作用。春化作用通过负调控FLC的转录及蛋白表达水平,促进拟南芥的某些晚花生态型和晚花突变体开花。主要介绍了FLC基因在春化途径中的关键作用,及其春化作用通过FLC基因与其它开花途径相联系等内容。     

植物同源盒基因的克隆与功能研究

同源盒基因在植物、动物、菌物的广泛存在说明这种结构在真核生物进化的早期就已出现,并暗示其具有重要功能。本文对植物同源盒基因的克隆与功能研究进行了综述,包括同源盒基因编码蛋白的结构特点、类型,并以玉米Knl、水稻OSH1及拟南芥STM为例,介绍了同源盒基因功能研究的现状。现有证据表明,同源盒基因与植物的发育过程有关。     

香蕉MuMADS1基因的生物信息学分析

通过筛选用采后0h和48h的香蕉果实构建的果实成熟的SSH(抑制差减杂交)文库,得到一条命名为MuMADS1长度为888bp的片段。通过互联网数据库及生物信息学分析工具对香蕉MuMADS1基因及其编码蛋白进行理化性质预测、序列与结构分析和功能预测。结果表明:MuMADS1基因编码蛋白分子式为C1171H1879N351O367S7,属于亲水的不稳定蛋白;保守结构域分析含有保守的MADS盒和半保守的K-box盒;二级结构主要是以α螺旋为主;具有多种磷酸化位点和核定位信号;同源性比较发现与许多植物的花器官决定基因具有较高的相似性,推测它们可能为同源基因,具有相似的生物学功能。     

水稻愈伤组织形态发生中的MADS盒基因的差异表达

采用MADS(MCM1-Agamous-Deficiens-SRF)盒基因家族功能区保守序列PCR引物,将水稻(Oryzasativa L.ssp indica)“珍汕97B”悬浮细胞、愈伤组织、分化愈伤组织和再生试管苗等不同形态发生的组织的mRNA反转录后选择性放大,经测序胶分离鉴定出一组差异表达的cDNA。对命名为RM1 cDNA的5＇端序列测定表明,RM1与典型的MADS基因——拟南芥agamous蛋白保守区一级结构同源性达63％,模拟二级结构相似性显著,初步确认RM1属于MADS基因家族成员。分子杂交证实,RM1在悬浮培养细胞中不表达,而在愈伤组织、分化愈伤组织和再生试管苗中活跃表达。     

植物同源异型基因及同源异型盒基因的研究进展

植物同源异型基因及同源异型盒基因是涉及植物个体发育调节的两类重要转录因子编码基因.近10年来的研究表明,这两类基因及其产物的结构与功能具有明显的差异.深入研究这两类基因的结构与功能对揭示植物的发育机制具有重要意义.     

CaMADS1, a MADS box gene expressed in the carpel of hazelnut

Hazelnut (Corylus avellana L.) is a species of economic interest that shows a peculiar floral biology. Unlike most of the angiosperms, which produce ovules during floral development such that they are ready for pollen at anthesis, hazelnut ovary development is delayed and triggered by compatible pollination. In order to elucidate the mechanisms regulating this unusual process and the role of the MADS box genes in ovary development, a cDNA library from pollinated styles of hazelnut was screened with a mixture of MADS box genes from different plant species. CaMADS1 (Corylus avellana MADS box), a floral-specific MADS box gene, was isolated, and characterized as belonging to the sub-family of the AGAMOUS genes. Northern blot, RT-PCR analyses and in situ hybridization experiments show a precise correlation between ovary development and CaMADS1 expression, indicating a role of this MADS box gene in the processes of floral organogenesis.     

The MADS box gene family in tomato: temporal expression during floral development, conserved secondary structures and homology with homeotic genes from Antirrhinum and Arabidopsis.

Five genes with homology to the floral homeotic genes deficiens of Antirrhinum and agamous of Arabidopsis were isolated from tomato. Each of the five genes is unique in the genome and could be localized to a different chromosome by RFLP mapping. Four of the tomato genes (hereafter TM) are flower-specific with distinguishable temporal expression. TM4 and TM8 are 'early', while TM5 and TM6 are 'late' genes. TM4 is homologous to squamous and TM6 is similar to deficiens, which are, respectively, 'early' and 'late' bona fide homeotic genes in Antirrhinum. The proteins encoded by the five tomato genes, like several known homeotic genes from other plants, contain within their N-terminus a highly conserved DNA-binding domain, the MADS box. All known plant MADS box genes also share, however, other properties. They all contain a central, moderately conserved, and rather basic domain, and a highly divergent or even missing C-terminal domain. Furthermore, molecular modelling predicts the presence of a conserved amphipatic alpha helix, at a constant distance from the MADS box in each of these proteins. The common properties of eight MADS box proteins from three plant families indicate that all their domains were coded for by the same ancestor gene. The sequence homology between pairs of MADS genes from different species indicates that the MADS ancestor gene multiplied and diverged in an ancestor plant common to several dicotyledon families.     

Diverse roles for MADS box genes in Arabidopsis development.

Members of the MADS box gene family play important roles in flower development from the early step of determining the identity of floral meristems to specifying the identity of floral organ primordia later in flower development. We describe here the isolation and characterization of six additional members of this family, increasing the number of reported Arabidopsis MADS box genes to 17. All 11 members reported prior to this study are expressed in flowers, and the majority of them are floral specific. RNA expression analyses of the six genes reported here indicate that two genes, AGL11 and AGL13 (AGL for AGAMOUS-like), are preferentially expressed in ovules, but each has a distinct expression pattern. AGL15 is preferentially expressed in embryos, with its onset at or before the octant stage early in embryo development. AGL12, AGL14, and AGL17 are all preferentially expressed in root tissues and therefore represent the only characterized MADS box genes expressed in roots. Phylogenetic analyses showed that the two genes expressed in ovules are closely related to previously isolated MADS box genes, whereas the four genes showing nonfloral expression are more distantly related. Data from this and previous studies indicate that in addition to their proven role in flower development, MADS box genes are likely to play roles in many other aspects of plant development.     

Evolution and function of MADS‐box genes involved in orchid floral development

Orchids are known for their beauty and complexity of flower and ecological strategies. The evolution in orchid floral morphology, structure, and physiological properties has held the fascination of botanists for centuries, from Darwin through to the present. In floral studies, MADS‐box genes contributing to the now famous ABCDE model of floral organ identity control have dominated conceptual thinking. The sophisticated orchid floral organization offers an opportunity to discover new variant genes and different levels of complexity to the ABCDE model. Recently, several remarkable research reports on orchid MADS‐box genes, especially B‐class MADS‐box genes, have revealed the evolutionary track and important functions on orchid floral development. Diversification and fixation of both paleoAP3 gene sequences and expression profiles might be explained by subfunctionalization and even neofunctionalization. Knowledge about MADS‐box genes encoding ABCDE functions in orchids will give insights into the highly evolved floral morphogenetic networks of orchids.     

Toward the analysis of the petunia MADS box gene family by reverse and forward transposon insertion mutagenesis approaches: B, C, and D floral organ identity functions require SEPALLATA-like MADS box genes in petunia

We have initiated a systematic functional analysis of the MADS box, intervening region, K domain, C domain-type MADS box gene family in petunia. The starting point for this has been a reverse-genetics approach, aiming to select for transposon insertions into any MADS box gene. We have developed and applied a family signature insertion screening protocol that is highly suited for this purpose, resulting in the isolation of 32 insertion mutants in 20 different MADS box genes. In addition, we identified three more MADS box gene insertion mutants using a candidate-gene approach. The defined insertion lines provide a sound foundation for a systematic functional analysis of the MADS box gene family in petunia. Here, we focus on the analysis of Floral Binding Protein2 (FBP2) and FBP5 genes that encode the E-function, which in Arabidopsis has been shown to be required for B and C floral organ identity functions. fbp2 mutants display sepaloid petals and ectopic inflorescences originating from the third floral whorl, whereas fbp5 mutants appear as wild type. In fbp2 fbp5 double mutants, reversion of floral organs to leaf-like organs is increased further. Strikingly, ovules are replaced by leaf-like structures in the carpel, indicating that in addition to the B- and C-functions, the D-function, which specifies ovule development, requires E-function activity. Finally, we compare our data with results obtained using cosuppression approaches and conclude that the latter might be less suited for assigning functions to individual members of the MADS box gene family.     

Overexpression of AGAMOUS-LIKE 28 (AGL28) promotes flowering by upregulating expression of floral promoters within the autonomous pathway

MADS box genes are known to perform important functions in the development of various plant organs. Although the functions of many MADS box genes have previously been elucidated, the biological function of the type I MADS box genes remains poorly understood. In order to understand the function and regulation of the type I MADS box genes, we conducted molecular genetic analyses of AGL28, a member of the Malpha class of type I genes. AGL28 was expressed in vegetative tissues in a photoperiod-independent manner, but not within the reproductive apex. This indicates that AGL28 plays a role in the vegetative phase. Overexpression of AGL28 caused precocious flowering via the upregulation of the expression of FCA and LUMINIDEPENDENS (LD), both floral promoters within the autonomous pathway. However, the loss of AGL28 function did not result in any obvious flowering time phenotype, which suggests that AGL28 may perform a redundant function. Collectively, our data suggest that AGL28 is a positive regulator of known floral promoters within the autonomous pathway in Arabidopsis.