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1.
Negative regulation of the Arabidopsis homeotic gene AGAMOUS by the APETALA2 product. 总被引:65,自引:0,他引:65
We characterized the distribution of AGAMOUS (AG) RNA during early flower development in Arabidopsis. Mutations in this homeotic gene cause the transformation of stamens to petals in floral whorl 3 and of carpels to another ag flower in floral whorl 4. We found that AG RNA is present in the stamen and carpel primordia but is undetectable in sepal and petal primordia throughout early wild-type flower development, consistent with the mutant phenotype. We also analyzed the distribution of AG RNA in apetela2 (ap2) mutant flowers. AP2 is a floral homeotic gene that is necessary for the normal development of sepals and petals in floral whorls 1 and 2. In ap2 mutant flowers, AG RNA is present in the organ primordia of all floral whorls. These observations show that the expression patterns of the Arabidopsis floral homeotic genes are in part established by regulatory interactions between these genes. 相似文献
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Patterns of gene duplication and functional evolution during the diversification of the AGAMOUS subfamily of MADS box genes in angiosperms 总被引:14,自引:0,他引:14
Members of the AGAMOUS (AG) subfamily of MIKC-type MADS-box genes appear to control the development of reproductive organs in both gymnosperms and angiosperms. To understand the evolution of this subfamily in the flowering plants, we have identified 26 new AG-like genes from 15 diverse angiosperm species. Phylogenetic analyses of these genes within a large data set of AG-like sequences show that ancient gene duplications were critical in shaping the evolution of the subfamily. Before the radiation of extant angiosperms, one event produced the ovule-specific D lineage and the well-characterized C lineage, whose members typically promote stamen and carpel identity as well as floral meristem determinacy. Subsequent duplications in the C lineage resulted in independent instances of paralog subfunctionalization and maintained functional redundancy. Most notably, the functional homologs AG from Arabidopsis and PLENA (PLE) from Antirrhinum are shown to be representatives of separate paralogous lineages rather than simple genetic orthologs. The multiple subfunctionalization events that have occurred in this subfamily highlight the potential for gene duplication to lead to dissociation among genetic modules, thereby allowing an increase in morphological diversity. 相似文献
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Identification of class B and class C floral organ identity genes from rice plants 总被引:25,自引:0,他引:25
The functions of two rice MADS-box genes were studied by the loss-of-function approach. The first gene, OsMADS4, shows a significant homology to members in the PISTILLATA (PI) family, which is required to specify petal and stamen identity. The second gene, OsMADS3, is highly homologous to the members in the AGAMOUS (AG) family that is essential for the normal development of the internal two whorls, the stamen and carpel, of the flower. These two rice MADS box cDNA clones were connected to the maize ubiquitin promoter in an antisense orientation and the fusion molecules were introduced to rice plants by the Agrobacterium-mediated transformation method. Transgenic plants expressing antisense OsMADS4 displayed alterations of the second and third whorls. The second-whorl lodicules, which are equivalent to the petals of dicot plants in grasses, were altered into palea/lemma-like organs, and the third whorl stamens were changed to carpel-like organs. Loss-of-function analysis of OsMADS3 showed alterations in the third and fourth whorls. In the third whorl, the filaments of the transgenic plants were changed into thick and fleshy bodies, similar to lodicules. Rather than making a carpel, the fourth whorl produced several abnormal flowers. These phenotypes are similar to those of the agamous and plena mutants in Arabidopsis and Antirrhinum, respectively. These results suggest that OsMADS4 belongs to the class B gene family and OsMADS3 belongs to the class C gene family of floral organ identity determination. 相似文献
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Winter KU Saedler H Theissen G 《The Plant journal : for cell and molecular biology》2002,31(4):457-475
Class B floral homeotic genes are involved in specifying stamen and petal identity in angiosperms (flowering plants). Here we report that gymnosperms, the closest relatives of the angiosperms, contain at least two different clades representing putative orthologues of class B genes, termed GGM2-like and DAL12-like genes. To obtain information about the functional conservation of the class B genes in seed plants, the representative of one of these clades from Gnetum, termed GGM2, was expressed under the control of the CaMV 35S promoter in Arabidopsis wild-type plants and in different class B mutants. In wild-type plants and in a conditional mutant grown at a permissive temperature, gain-of-function phenotypes were obtained in whorls 1 and 4, where class B genes are usually not expressed. In contrast, loss-of-function phenotypes were observed in whorls 2 and 3, where class B genes are expressed. In different class B gene null mutants of Arabidopsis, and in the conditional B mutant grown at the non-permissive temperature, a partial complementation of the mutant phenotype was obtained. In situ hybridization studies and class B gene promoter test fusion experiments demonstrated that the gain-of-function phenotypes are not due to an upregulation of the endogenous B genes from Arabidopsis, and hence probably involve interactions between GGM2 protein homodimers and class B protein target genes other than the Arabidopsis class B genes itself. To our knowledge, this is the first time that partial complementation of a homeotic mutant by an orthologous gene from a distantly related species has been reported. These data suggest that GGM2 has a function in the gymnosperm Gnetum which is related to that of class B floral organ identity genes of angiosperms. That function may be in the specification of male reproductive organ identity, and in distinguishing male from female reproductive organs. 相似文献
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To B or Not to B a flower: the role of DEFICIENS and GLOBOSA orthologs in the evolution of the angiosperms 总被引:10,自引:0,他引:10
DEFICIENS (DEF) and GLOBOSA (GLO) function in petal and stamen organ identity in Antirrhinum and are orthologs of APETALA3 and PISTILLATA in Arabidopsis. These genes are known as B-function genes for their role in the ABC genetic model of floral organ identity. Phylogenetic analyses show that DEF and GLO are closely related paralogs, having originated from a gene duplication event after the separation of the lineages leading to the extant gymnosperms and the extant angiosperms. Several additional gene duplications followed, providing multiple potential opportunities for functional divergence. In most angiosperms studied to date, genes in the DEF/GLO MADS-box subfamily are expressed in the petals and stamens during flower development. However, in some angiosperms, the expression of DEF and GLO orthologs are occasionally observed in the first and fourth whorls of flowers or in nonfloral organs, where their function is unknown. In this article we review what is known about function, phylogeny, and expression in the DEF/GLO subfamily to examine their evolution in the angiosperms. Our analyses demonstrate that although the primary role of the DEF/GLO subfamily appears to be in specifying the stamens and inner perianth, several examples of potential sub- and neofunctionalization are observed. 相似文献
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Multiple AGAMOUS homologs from cucumber and petunia differ in their ability to induce reproductive organ fate. 总被引:9,自引:0,他引:9 下载免费PDF全文
M M Kater L Colombo J Franken M Busscher S Masiero M M Van Lookeren Campagne G C Angenent 《The Plant cell》1998,10(2):171-182
The C function in Arabidopsis, which specifies stamen and carpel identity, is represented by a single gene called AGAMOUS (AG). From both petunia and cucumber, two MADS box genes have been isolated. Both share a high degree of amino acid sequence identity with the Arabidopsis AG protein. Their roles in specifying stamen and carpel identity have been studied by ectopic expression in petunia, resulting in plants with different floral phenotypes. Cucumber MADS box gene 1 (CUM1) induced severe homeotic transformations of sepals into carpelloid structures and petals into stamens, which is similar to ectopic AG expression in Arabidopsis plants. Overexpression of the other cucumber AG homolog, CUM10, resulted in plants with partial transformations of the petals into antheroid structures, indicating that CUM10 is also able to promote floral organ identity. From the two petunia AG homologs pMADS3 and Floral Binding Protein gene 6 (FBP6), only pMADS3 was able to induce homeotic transformations of sepals and petals. Ectopic expression of both pMADS3 and FBP6, as occurrs in the petunia homeotic mutant blind, phenocopies the pMADS3 single overexpresser plants, indicating that there is no additive effect of concerted expression. This study demonstrates that in petunia and cucumber, multiple AG homologs exist, although they differ in their ability to induce reproductive organ fate. 相似文献
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MADS-box protein complexes control carpel and ovule development in Arabidopsis 总被引:28,自引:0,他引:28 下载免费PDF全文
Favaro R Pinyopich A Battaglia R Kooiker M Borghi L Ditta G Yanofsky MF Kater MM Colombo L 《The Plant cell》2003,15(11):2603-2611
The AGAMOUS (AG) gene is necessary for stamen and carpel development and is part of a monophyletic clade of MADS-box genes that also includes SHATTERPROOF1 (SHP1), SHP2, and SEEDSTICK (STK). Here, we show that ectopic expression of either the STK or SHP gene is sufficient to induce the transformation of sepals into carpeloid organs bearing ovules. Moreover, the fact that these organ transformations occur when the STK gene is expressed ectopically in ag mutants shows that STK can promote carpel development in the absence of AG activity. We also show that STK, AG, SHP1, and SHP2 can form multimeric complexes and that these interactions require the SEPALLATA (SEP) MADS-box proteins. We provide genetic evidence for this role of the SEP proteins by showing that a reduction in SEP activity leads to the loss of normal ovule development, similar to what occurs in stk shp1 shp2 triple mutants. Together, these results indicate that the SEP proteins, which are known to form multimeric complexes in the control of flower organ identity, also form complexes to control normal ovule development. 相似文献
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The Norway spruce MADS-box genes DAL11, DAL12 and DAL13 are phylogenetically related to the angiosperm B-function MADS-box genes: genes that act together with A-function genes in specifying petal identity and with C-function genes in specifying stamen identity to floral organs. In this report we present evidence to suggest that the B-gene function in the specification of identity of the pollen-bearing organs has been conserved between conifers and angiosperms. Expression of DAL11 or DAL12 in transgenic Arabidopsis causes phenotypic changes which partly resemble those caused by ectopic expression of the endogenous B-genes. In similar experiments, flowers of Arabidopsis plants expressing DAL13 showed a different homeotic change in that they formed ectopic anthers in whorls one, two or four. We also demonstrate the capacity of the spruce gene products to form homodimers, and that DAL11 and DAL13 may form heterodimers with each other and with the Arabidopsis B-protein AP3, but not with PI, the second B-gene product in Arabidopsis. In situ hybridization experiments show that the conifer B-like genes are expressed specifically in developing pollen cones, but differ in both temporal and spatial distribution patterns. These results suggest that the B-function in conifers is dual and is separated into a meristem identity and an organ identity function, the latter function possibly being independent of an interaction with the C-function. Thus, even though an ancestral B-function may have acted in combination with C to specify micro- and megasporangia, the B-function has evolved differently in conifers and angiosperms. 相似文献