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Toshiro Ito – One of the best experts on this subject based on the ideXlab platform.

  • Regulation of floral meristem activity through the interaction of Agamous, SUPERMAN, and CLAVATA3 in Arabidopsis.
    Plant reproduction, 2017
    Co-Authors: Akira Uemura, Nobutoshi Yamaguchi, Wan-yi Wee, Yasunori Ichihashi, Takamasa Suzuki, Arisa Shibata, Ken Shirasu, Toshiro Ito
    Abstract:

    Floral meristem size is redundantly controlled by CLAVATA3, Agamous , and SUPERMAN in Arabidopsis. The proper regulation of floral meristem activity is key to the formation of optimally sized flowers with a fixed number of organs. In Arabidopsis thaliana, multiple regulators determine this activity. A small secreted peptide, CLAVATA3 (CLV3), functions as an important negative regulator of stem cell activity. Two transcription factors, Agamous (AG) and SUPERMAN (SUP), act in different pathways to regulate the termination of floral meristem activity. Previous research has not addressed the genetic interactions among these three genes. Here, we quantified the floral developmental stage-specific phenotypic consequences of combining mutations of AG, SUP, and CLV3. Our detailed phenotypic and genetic analyses revealed that these three genes act in partially redundant pathways to coordinately modulate floral meristem sizes in a spatial and temporal manner. Analyses of the ag sup clv3 triple mutant, which developed a mass of undifferentiated cells in its flowers, allowed us to identify downstream targets of AG with roles in reproductive development and in the termination of floral meristem activity. Our study highlights the role of AG in repressing genes that are expressed in organ initial cells to control floral meristem activity.

  • Floral stem cell termination involves the direct regulation of Agamous by PERIANTHIA.
    Development (Cambridge England), 2009
    Co-Authors: Pradeep Das, Toshiro Ito, Frank Wellmer, Teva Vernoux, Annick Dedieu, Jan Traas, Elliot M Meyerowitz
    Abstract:

    In Arabidopsis, the population of stem cells present in young flower buds is lost after the production of a fixed number of floral organs. The precisely timed repression of the stem cell identity gene WUSCHEL (WUS) by the floral homeotic protein Agamous (AG) is a key part of this process. In this study, we report on the identification of a novel input into the process of floral stem cell regulation. We use genetics and chromatin immunoprecipitation assays to demonstrate that the bZIP transcription factor PERIANTHIA (PAN) plays a role in regulating stem cell fate by directly controlling AG expression and suggest that this activity is spatially restricted to the centermost region of the AG expression domain. These results suggest that the termination of floral stem cell fate is a multiply redundant process involving loci with unrelated floral patterning functions.

  • The homeotic protein Agamous controls microsporogenesis by regulation of SPOROCYTELESS
    Nature, 2004
    Co-Authors: Toshiro Ito, Jose Luis Riechmann, Frank Wellmer, Pradeep Das, Natsuko Ito, Marcio Alves-ferreira, Elliot M Meyerowitz
    Abstract:

    The Arabidopsis homeotic gene Agamous (AG) is necessary for the specification of reproductive organs (stamens and carpels) during the early steps of flower development. AG encodes a transcription factor of the MADS-box family that is expressed in stamen and carpel primordia. At later stages of development, AG is expressed in distinct regions of the reproductive organs. This suggests that AG might function during the maturation of stamens and carpels, as well as in their early development. However, the developmental processes that AG might control during organogenesis and the genes that are regulated by this factor are largely unknown. Here we show that microsporogenesis, the process leading to pollen formation, is induced by AG through activation of the SPOROCYTELESS gene (SPL, also known as NOZZLE,NZZ), a regulator of sporogenesis. Furthermore, we demonstrate that SPL can induce microsporogenesis in the absence of AG function, suggesting that AG controls a specific process during organogenesis by activating another regulator that performs a subset of its functions.

Elliot M Meyerowitz – One of the best experts on this subject based on the ideXlab platform.

  • Floral stem cell termination involves the direct regulation of Agamous by PERIANTHIA.
    Development (Cambridge England), 2009
    Co-Authors: Pradeep Das, Toshiro Ito, Frank Wellmer, Teva Vernoux, Annick Dedieu, Jan Traas, Elliot M Meyerowitz
    Abstract:

    In Arabidopsis, the population of stem cells present in young flower buds is lost after the production of a fixed number of floral organs. The precisely timed repression of the stem cell identity gene WUSCHEL (WUS) by the floral homeotic protein Agamous (AG) is a key part of this process. In this study, we report on the identification of a novel input into the process of floral stem cell regulation. We use genetics and chromatin immunoprecipitation assays to demonstrate that the bZIP transcription factor PERIANTHIA (PAN) plays a role in regulating stem cell fate by directly controlling AG expression and suggest that this activity is spatially restricted to the centermost region of the AG expression domain. These results suggest that the termination of floral stem cell fate is a multiply redundant process involving loci with unrelated floral patterning functions.

  • The homeotic protein Agamous controls microsporogenesis by regulation of SPOROCYTELESS
    Nature, 2004
    Co-Authors: Toshiro Ito, Jose Luis Riechmann, Frank Wellmer, Pradeep Das, Natsuko Ito, Marcio Alves-ferreira, Elliot M Meyerowitz
    Abstract:

    The Arabidopsis homeotic gene Agamous (AG) is necessary for the specification of reproductive organs (stamens and carpels) during the early steps of flower development. AG encodes a transcription factor of the MADS-box family that is expressed in stamen and carpel primordia. At later stages of development, AG is expressed in distinct regions of the reproductive organs. This suggests that AG might function during the maturation of stamens and carpels, as well as in their early development. However, the developmental processes that AG might control during organogenesis and the genes that are regulated by this factor are largely unknown. Here we show that microsporogenesis, the process leading to pollen formation, is induced by AG through activation of the SPOROCYTELESS gene (SPL, also known as NOZZLE,NZZ), a regulator of sporogenesis. Furthermore, we demonstrate that SPL can induce microsporogenesis in the absence of AG function, suggesting that AG controls a specific process during organogenesis by activating another regulator that performs a subset of its functions.

  • Repression of Agamous-LIKE 24 is a crucial step in promoting flower development.
    Nature genetics, 2004
    Co-Authors: Toshiro Ito, Frank Wellmer, Elliot M Meyerowitz
    Abstract:

    Flower development begins as floral meristems arise in succession on the flank of the inflorescence meristem. Floral meristem identity genes LEAFY (LFY) and APETALA1 (AP1) promote establishment and maintenance of floral identity in newly formed floral primordia. Without their activity, the floral primordia develop with inflorescence characteristics. The underlying molecular-genetic mechanism is unknown. Here we show that these phenotypes are due in large part to the ectopic expression of Agamous-LIKE 24 (AGL24), a central regulator of floral meristem identity. We present evidence that AGL24 is an early target of transcriptional repression by LFY and AP1. Without such repression, continued AGL24 expression in floral meristems is sufficient to cause floral reversion regardless of the activation of floral organ identity genes. This indicates that LFY and AP1 promote floral development not only by positively regulating genes activated in flower development, but also by repressing AGL24, a promoter of inflorescence fate.

Kiyotaka Okada – One of the best experts on this subject based on the ideXlab platform.

  • a serine threonine protein kinase gene isolated by an in vivo binding procedure using the arabidopsis floral homeotic gene product Agamous
    Plant and Cell Physiology, 1997
    Co-Authors: Toshiro Ito, Yoshiro Shimura, Naoki Takahashi, Kiyotaka Okada
    Abstract:

    During the course of characterizing fragments bound to an Arabidopsis floral homeotic protein Agamous in vivo, a gene encoding a putative serine/threonine protein kinase was found on one of the fragments. The deduced 426 amino acid residues of the gene, named APK2a, are 65% identical to a previously reported Arabidopsis serine/ threonine protein kinase, APKla. The gene is composed of 6 exons and maps at 10 cM from the upper end of chromosome 1. Northern hybridization experiments indicated that the gene is strongly expressed in leaves, moderately in roots, and very weakly in flowers. Further in situ analysis of the expression in floral buds showed that the APK2a gene is expressed at pedicels, is not expressed at the floral organ primordia of wild type floral buds, but is moderately expressed in the floral organ primordia of the Agamous mutant. In vitro binding assay suggests that the Agamous protein binds to a sequence similar to, but different from, the known MADS-binding consensus sequences, the CArG box, located 3′ downstream of the APK2a gene. These results suggest that APK2a gene expression is negatively regulated by the AG protein. A close homologue of the APK2a gene, named APK2b, was also isolated from the Arabidopsis cDNA library. The expression pattern of the APK2b gene differs from that of APK2a. It is strongly expressed in leaves, moderately in flowers, and weakly in roots.

  • A Serine/Threonine Protein Kinase Gene Isolated by an in vivo Binding Procedure Using the Arabidopsis Floral Homeotic Gene Product, Agamous
    Plant & cell physiology, 1997
    Co-Authors: Toshiro Ito, Yoshiro Shimura, Naoki Takahashi, Kiyotaka Okada
    Abstract:

    During the course of characterizing fragments bound to an Arabidopsis floral homeotic protein Agamous in vivo, a gene encoding a putative serine/threonine protein kinase was found on one of the fragments. The deduced 426 amino acid residues of the gene, named APK2a, are 65% identical to a previously reported Arabidopsis serine/ threonine protein kinase, APKla. The gene is composed of 6 exons and maps at 10 cM from the upper end of chromosome 1. Northern hybridization experiments indicated that the gene is strongly expressed in leaves, moderately in roots, and very weakly in flowers. Further in situ analysis of the expression in floral buds showed that the APK2a gene is expressed at pedicels, is not expressed at the floral organ primordia of wild type floral buds, but is moderately expressed in the floral organ primordia of the Agamous mutant. In vitro binding assay suggests that the Agamous protein binds to a sequence similar to, but different from, the known MADS-binding consensus sequences, the CArG box, located 3′ downstream of the APK2a gene. These results suggest that APK2a gene expression is negatively regulated by the AG protein. A close homologue of the APK2a gene, named APK2b, was also isolated from the Arabidopsis cDNA library. The expression pattern of the APK2b gene differs from that of APK2a. It is strongly expressed in leaves, moderately in flowers, and weakly in roots.

  • Nucleotide sequences recognized by the Agamous MADS domain of Arabidopsis thaliana in vitro
    The Plant journal : for cell and molecular biology, 1993
    Co-Authors: Hideaki Shiraishi, Kiyotaka Okada, Yoshiro Shimura
    Abstract:

    The Agamous gene of Arabidopsis thaliana is a homeotic gene involved in the development of stamens and carpels. This gene encodes a putative DNA-bindbinding protprotein sharing a homologous region with the DNA-binding domains, MADS boxes, of yeast MCM1 and mammalian SRF. To examine the DNA-binding activity of the Agamous protein, double-stranded oligonucleotides with random sequences of 40 bp in the central region were synthesized and mixed with the Agamous MADS domain overproduced in Escherichia coli. Oligonucleotides which bound to the MADS domain were recovered by repeated immunoprecipitation with an antibody which recognizes the overproduced protein. From a comparison of the recovered DNA sequences, the consensus sequence of the high-affinity binding-sites for the Agamous MADS domain was determined to be 5′-TT(A/T/G) CC(A/T)6GG(A/T/C)AA-3′. DNase I footprinting and methylation interference experiments showed that the MADS domain binds to this motif. Comparisons with the binding-site sequences of other MADS-box proteins revealed that the MCM1 binding-sites in a-mating type-specific promoters of Saccharomyces cerevisiae show similarities with the binding-site sequence of the Agamous MADS domain. A synthetic MCM1 binding-site in the upstream region of the STE2 gene is recognized by the Agamous MADS domain.

Rafael Lozano – One of the best experts on this subject based on the ideXlab platform.

  • TOMATO Agamous1 and ARLEQUIN/TOMATO Agamous-LIKE1 MADS-box genes have redundant and divergent functions required for tomato reproductive development.
    Plant Molecular Biology, 2016
    Co-Authors: Estela Giménez, Laura Castañeda, Benito Pineda, Irvin L. Pan, Vicente Moreno, Trinidad Angosto, Rafael Lozano
    Abstract:

    Within the tomato MADS-box gene family, TOMATO Agamous1 (TAG1) and ARLEQUIN/TOMATO Agamous LIKE1 (hereafter referred to as TAGL1) are, respectively, members of the euAG and PLE lineages of the Agamous clade. They perform crucial functions specifying stamen and carpel development in the flower and controlling late fruit development. To gain insight into the roles of TAG1 and TAGL1 genes and to better understand their functional redundancy and diversification, we characterized single and double RNAi silencing lines of these genes and analyzed expression profiles of regulatory genes involved in reproductive development. Double RNAi lines did show cell abnormalities in stamens and carpels and produced extremely small fruit-like organs displaying some sepaloid features. Expression analyses indicated that TAG1 and TAGL1 act together to repress fourth whorl sepal development, most likely through the MACROCALYX gene. Results also proved that TAG1 and TAGL1 have diversified their functions in fruit development: while TAG1 controls placenta and seed formation, TAGL1 participates in cuticle development and lignin biosynthesis inhibition. It is noteworthy that both TAG1 and double RNAi plants lacked seed development due to abnormalities in pollen formation. This seedless phenotype was not associated with changes in the expression of B-class stamen identity genes Tomato MADS-box 6 and Tomato PISTILLATA observed in silencing lines, suggesting that other regulatory factors should participate in pollen formation. Taken together, results here reported support the idea that both redundant and divergent functions of TAG1 and TAGL1 genes are needed to control tomato reproductive development.

  • tomato Agamous1 and arlequin tomato Agamous like1 mads box genes have redundant and divergent functions required for tomato reproductive development
    Plant Molecular Biology, 2016
    Co-Authors: Estela Giménez, Laura Castañeda, Benito Pineda, Irvin L. Pan, Vicente Moreno, Trinidad Angosto, Rafael Lozano
    Abstract:

    Within the tomato MADS-box gene family, TOMATO Agamous1 (TAG1) and ARLEQUIN/TOMATO Agamous LIKE1 (hereafter referred to as TAGL1) are, respectively, members of the euAG and PLE lineages of the Agamous clade. They perform crucial functions specifying stamen and carpel development in the flower and controlling late fruit development. To gain insight into the roles of TAG1 and TAGL1 genes and to better understand their functional redundancy and diversification, we characterized single and double RNAi silencing lines of these genes and analyzed expression profiles of regulatory genes involved in reproductive development. Double RNAi lines did show cell abnormalities in stamens and carpels and produced extremely small fruit-like organs displaying some sepaloid features. Expression analyses indicated that TAG1 and TAGL1 act together to repress fourth whorl sepal development, most likely through the MACROCALYX gene. Results also proved that TAG1 and TAGL1 have diversified their functions in fruit development: while TAG1 controls placenta and seed formation, TAGL1 participates in cuticle development and lignin biosynthesis inhibition. It is noteworthy that both TAG1 and double RNAi plants lacked seed development due to abnormalities in pollen formation. This seedless phenotype was not associated with changes in the expression of B-class stamen identity genes Tomato MADS-box 6 and Tomato PISTILLATA observed in silencing lines, suggesting that other regulatory factors should participate in pollen formation. Taken together, results here reported support the idea that both redundant and divergent functions of TAG1 and TAGL1 genes are needed to control tomato reproductive development.

Martin M. Kater – One of the best experts on this subject based on the ideXlab platform.

  • Functionally Divergent Splicing Variants of the Rice Agamous Ortholog OsMADS3 Are Evolutionary Conserved in Grasses.
    Frontiers in plant science, 2020
    Co-Authors: Ludovico Dreni, Andrea Ravasio, Nahuel Gonzalez-schain, Sara Jacchia, Glacy Jaqueline Da Silva, Stefano Ricagno, Rosaria Russo, Francesca Caselli, Veronica Gregis, Martin M. Kater
    Abstract:

    Within the MADS-box gene family, the Agamous-subfamily genes are particularly important for plant reproduction, because they control stamen and carpel identity. A number of studies in the last three decades have demonstrated that the Agamous (AG) function has been conserved during land plant evolution. However, gene duplication events have led to subfunctionalization and neofunctionalization of AG-like genes in many species. Here we show that alternative splicing in Oryza sativa produces two variants of the AG ortholog OsMADS3 which differ in just one serine residue, S109. Interestingly, this alternative splicing variant is conserved and specific to the grass family. Since in eudicots the S109 residue is absent in AG proteins, stamen and carpel identity determination activity of the two rice isoforms was tested in Arabidopsis thaliana. These experiments revealed that only the eudicot-like OsMADS3 isoform, lacking the serine residue, had ability to specify stamens and carpels in ag mutant flowers, suggesting an important functional role for the serine residue at position 109 in AG proteins of grasses.

  • MADS reloaded : evolution of the Agamous subfamily genes
    The New phytologist, 2013
    Co-Authors: Ludovico Dreni, Martin M. Kater
    Abstract:

    Agamous subfamily proteins are encoded by MADS-box family genes. They have been shown to play key roles in the determination of reproductive floral organs such as stamens, carpels and ovules. However, they also play key roles in ensuring a fixed number of floral organs by controlling floral meristem determinacy. Recently, an enormous amount of sequence data for nonmodel species have become available together with functional data on Agamous subfamily members in many species. Here, we give a detailed overview of the most important information about this interesting gene subfamily and provide new insights into its evolution.

  • The Ins and Outs of the Rice Agamous Subfamily
    Molecular plant, 2013
    Co-Authors: Ludovico Dreni, Michela Osnato, Martin M. Kater
    Abstract:

    ABSTRACT Genes of the Agamous subfamily have been shown to play crucial roles in reproductive organ identity determination, fruit, and seed development. They have been deeply studied in eudicot species and especially in Arabidopsis . Recently, the Agamous subfamily of rice has been studied for their role in flower development and an enormous amount of data has been generated. In this review, we provide an overview of these data and discuss the conservation of gene functions between rice and Arabidopsis . SUMMARY Recently, extensive data about the function of rice MADS-box transcription factor encoding genes belonging to the Agamous subfamily have been published. Here, we review these data focusing on their role in the formation of reproductive organs and the floral meristem.