scholarly journals Epidermal control of floral organ identity by class B homeotic genes in Antirrhinum and Arabidopsis

Development ◽  
2001 ◽  
Vol 128 (14) ◽  
pp. 2661-2671
Author(s):  
Nadia Efremova ◽  
Marie-Christine Perbal ◽  
Alexander Yephremov ◽  
Winfried A. Hofmann ◽  
Heinz Saedler ◽  
...  
Keyword(s):  
Transgene Expression ◽  
Transgenic Arabidopsis ◽  
Cell Communication ◽  
Cell Types ◽  
Floral Organ ◽  
Epidermal Differentiation ◽  
Homeotic Genes ◽  
Organ Identity ◽  
Class B ◽  
Functional Homologues

To assess the contribution of the epidermis to the control of petal and stamen organ identity, we have used transgenic Antirrhinum and Arabidopsis plants that expressed the Antirrhinum class B homeotic transcription factors DEFICIENS (DEF) and GLOBOSA (GLO) in the epidermis. Transgene expression was controlled by the ANTIRRHINUM FIDDLEHEAD (AFI) promoter, which directs gene expression to the L1 meristematic layer and, later, to the epidermis of differentiating organs. Transgenic epidermal DEF and GLO chimeras display similar phenotypes, suggesting similar epidermal contributions by the two class B genes in Antirrhinum. Epidermal B function autonomously controls the differentiation of Antirrhinum petal epidermal cell types, but cannot fully control the pattern of cell divisions and the specification of sub-epidermal petal cell-identity by epidermal signalling. This non-autonomous control is enhanced if the endogenous class B genes can be activated from the epidermis. The developmental influence of epidermal B function in Antirrhinum stamen development is very limited. In contrast, epidermal B function in Arabidopsis can control most if not all epidermal and sub-epidermal differentiation events in petals and stamens, without any contribution from the endogenous class B genes. Possible reasons for differences in the efficacy of B-function-mediated cell communication between the two species are discussed. Interestingly, our experiments uncovered partial incompatibility between class B functional homologues. Although the DEFICIENS/PISTILLATA heterodimer is functional in transgenic Arabidopsis plants, the APETALA3/GLOBOSA heterodimer is not.

HUA ENHANCER2, a putative DExH-box RNA helicase, maintains homeotic B and C gene expression inArabidopsis

Development ◽  
2002 ◽  
Vol 129 (7) ◽  
pp. 1569-1581 ◽  
Author(s):  
Tamara L. Western ◽  
Yulan Cheng ◽  
Jun Liu ◽  
Xuemei Chen
Keyword(s):  
Gene Expression ◽  
Floral Organ ◽  
Rna Helicase ◽  
Reproductive Organ ◽  
Recessive Mutation ◽  
Homeotic Genes ◽  
Organ Identity ◽  
Quadruple Mutant ◽  
Normal Spacing ◽  
Floral Homeotic

Reproductive organ identity in Arabidopsis is controlled by the B, C and SEPALLATA classes of floral homeotic genes. We have identified a recessive mutation in a novel gene, HUA ENHANCER2, which, when combined with mutations in two weak class C genes, HUA1 and HUA2, leads to the production of third whorl sepal-petal-stamens and fourth whorl sepal-carpels. Quadruple mutant analysis and in situ localization of A, B, C and SEPALLATA floral homeotic RNAs suggest that HUA ENHANCER2 is required for the maintenance of B and C gene expression in the reproductive whorls. In addition to its role in floral homeotic gene expression, HUA ENHANCER2 is required for normal spacing and number of perianth organ primordia. We show that HUA ENHANCER2 encodes a putative DExH-box RNA helicase that is expressed in specific patterns in the inflorescence meristem and developing flowers. As a possible ortholog of the yeast exosome-associated protein, Dob1p (Mtr4p), HUA ENHANCER2 may affect floral organ spacing and identity through the regulation of protein synthesis or mRNA degradation. Therefore, our studies on HUA ENHANCER2 not only demonstrate that B and C gene expression is established and maintained separately, but also implicate the existence of post-transcriptional mechanisms in the maintenance of B and C gene expression.

scholarly journals Divergence of function and regulation of class B floral organ identity genes.

1997 ◽  
Vol 9 (4) ◽  
pp. 559-570 ◽  
Author(s):  
A Samach ◽  
S E Kohalmi ◽  
P Motte ◽  
R Datla ◽  
G W Haughn
Keyword(s):  
Floral Organ ◽  
Floral Organ Identity ◽  
Organ Identity ◽  
Class B ◽  
Floral Organ Identity Genes

scholarly journals Divergence of Function and Regulation of Class B Floral Organ Identity Genes

1997 ◽  
Vol 9 (4) ◽  
pp. 559
Author(s):  
Alon Samach ◽  
Susanne E. Kohalmi ◽  
Patrick Motte ◽  
Raju Datla ◽  
George W. Haughn
Keyword(s):  
Floral Organ ◽  
Floral Organ Identity ◽  
Organ Identity ◽  
Class B ◽  
Floral Organ Identity Genes

scholarly journals Molecular Evolution of Genes Controlling Petal and Stamen Development: Duplication and Divergence Within the APETALA3 and PISTILLATA MADS-Box Gene Lineages

Genetics ◽  
1998 ◽  
Vol 149 (2) ◽  
pp. 765-783 ◽  
Author(s):  
Elena M Kramer ◽  
Robert L Dorit ◽  
Vivian F Irish
Keyword(s):  
Morphological Evolution ◽  
Floral Organ ◽  
Duplication Event ◽  
Homeotic Genes ◽  
Mads Box ◽  
Floral Organ Identity ◽  
Organ Identity ◽  
Duplication Events ◽  
Mads Box Gene ◽  
Dicot Species

Abstract The specification of floral organ identity in the higher dicots depends on the function of a limited set of homeotic genes, many of them members of the MADS-box gene family. Two such genes, APETALA3 (AP3) and PISTILLATA (PI), are required for petal and stamen identity in Arabidopsis; their orthologs in Antirrhinum exhibit similar functions. To understand how changes in these genes may have influenced the morphological evolution of petals and stamens, we have cloned twenty-six homologs of the AP3 and PI genes from two higher eudicot and eleven lower eudicot and magnolid dicot species. The sequences of these genes reveal the presence of characteristic PI- and AP3-specific motifs. While the PI-specific motif is found in all of the PI genes characterized to date, the lower eudicot and magnolid dicot AP3 homologs contain distinctly different motifs from those seen in the higher eudicots. An analysis of all the available AP3 and PI sequences uncovers multiple duplication events within each of the two gene lineages. A major duplication event in the AP3 lineage coincides with the base of the higher eudicot radiation and may reflect the evolution of a petal-specific AP3 function in the higher eudicot lineage.

scholarly journals AINTEGUMENTA and AINTEGUMENTA-LIKE6 directly regulate floral homeotic and growth genes in young flowers

2020 ◽  
Author(s):  
Beth A. Krizek ◽  
Alexis T. Bantle ◽  
Jorman M. Heflin ◽  
Han Han ◽  
Nowlan H. Freese ◽  
...  
Keyword(s):  
Transcription Factors ◽  
Binding Sites ◽  
Floral Organ ◽  
Homeotic Genes ◽  
Flower Primordia ◽  
Floral Organ Identity ◽  
Floral Organogenesis ◽  
Floral Homeotic Genes ◽  
Organ Identity ◽  
Floral Homeotic

AbstractArabidopsis flower primordia give rise to floral organ primordia in stereotypical positions within four concentric whorls. Floral organ primordia in each whorl undergo distinct developmental programs to become one of four organ types (sepals, petals, stamens, and carpels). The Arabidopsis transcription factors AINTEGUMENTA (ANT) and AINTEGUMENTA-LIKE6 (AIL6) play critical and partially overlapping roles during floral organogenesis. They are required for correct positioning of floral organ initiation, contribute to the specification of floral organ identity, and regulate the growth and morphogenesis of developing floral organs. To gain insight into the molecular means by which ANT and AIL6 contribute to floral organogenesis, we identified the genome-wide binding sites of both ANT and AIL6 in stage 3 flower primordia, the developmental stage at which sepal primordia become visible and class B and C floral homeotic genes are first expressed. AIL6 binds to a subset of ANT sites, suggesting that AIL6 regulates some but not all of the same target genes as ANT. ANT and AIL6 binding sites are associated with genes involved in many biological processes related to meristem and flower organ development. Comparison of genes associated with both ANT and AIL6 ChIP-Seq peaks and those differentially expressed after perturbation of ANT or AIL6 activity identified likely direct targets of ANT and AIL6 regulation. These include the floral homeotic genes APETALA3 (AP3) and AGAMOUS (AG) and four growth regulatory genes: BIG BROTHER (BB), ROTUNDIFOLIA3 (ROT3), ANGUSTIFOLIA3/GRF INTERACTING FACTOR (AN3/GIF1), and XYLOGLUCAN ENDOTRANSGLUCOLSYLASE/HYDROLASE9 (XTH9).One Sentence SummaryThe transcription factors ANT and AIL6 directly regulate genes involved in different aspects of flower development including genes that specify floral organ identity and those that regulate growth.

scholarly journals The Arabidopsis homeotic genes APETALA3 and PISTILLATA are sufficient to provide the B class organ identity function

Development ◽  
1996 ◽  
Vol 122 (1) ◽  
pp. 11-22 ◽  
Author(s):  
B.A. Krizek ◽  
E.M. Meyerowitz
Keyword(s):  
Mosaic Virus ◽  
Cauliflower Mosaic Virus ◽  
35S Promoter ◽  
Homeotic Genes ◽  
Identity Function ◽  
Leaf Curling ◽  
Class A ◽  
Organ Identity ◽  
Class B ◽  
Additional Role

The class B organ identity genes, APETALA3 and PISTILLATA, are required to specify petal and stamen identity in the Arabidopsis flower. We show here that the activities of these two genes are sufficient to specify petals and stamens in flowers, in combination with the class A and C genes, respectively. Flowers of plants constitutively expressing both PISTILLATA and APETALA3 under the control of the 35S promoter from cauliflower mosaic virus consist of two outer whorls of petals and inner whorls of stamens. These plants also exhibit vegetative phenotypes that are not present in either of the singly (APETALA3 or PISTILLATA) overexpressing lines. These phenotypes include leaf curling and the partial conversion of later-arising cauline leaves to petals. The presence of additional floral whorls in flowers ectopically expressing APETALA3 and PISTILLATA and the rescue of missing organs in class A mutants by ectopic B function suggest that APETALA3 and PISTILLATA play an additional role in proliferation of the floral meristem.

scholarly journals STYLOSA and FISTULATA: regulatory components of the homeotic control of Antirrhinum floral organogenesis

Development ◽  
1998 ◽  
Vol 125 (1) ◽  
pp. 71-84 ◽  
Author(s):  
P. Motte ◽  
H. Saedler ◽  
Z. Schwarz-Sommer
Keyword(s):  
Ectopic Expression ◽  
Reproductive Organs ◽  
Negative Control ◽  
Homeotic Genes ◽  
Expression Domain ◽  
Floral Organogenesis ◽  
Organ Identity ◽  
Class B ◽  
Spatial Differences ◽  
Meristem Identity

The identity and developmental pattern of the four organ types constituting the flower is governed by three developmental functions, A, B and C, which are defined by homeotic genes and established in two adjacent whorls. In this report we morphologically and genetically characterise mutants of two genes, STYLOSA (STY) and FISTULATA (FIS) which control floral homeotic meristem- and organ-identity genes and developmental events in all floral whorls. The morphology of the reproductive organs in the first and second whorls of sty fis double mutant flowers indicate that the two genes are part of the mechanism to prevent ectopic expression of the C-function in the perianth of wild-type flowers. This is verified by the detection of the expansion of the expression domain of the class C gene PLENA (PLE) towards the perianth. Interestingly, in the second whorl of sty and fis mutants, spatial differences in stamenoid features and in the pattern of ectopic expression of the PLE gene were observed. This suggests that, with respect to the negative control of PLE, petals are composed of two regions, a lateral and a central one. Mutation in ple is epistatic to most of the sty/fis-related homeotic defects. PLE, however, is not the primary target of STY/FIS control, because dramatic reduction of expression of FIMBRIATA, meristem identity genes (FLORICAULA and SQUAMOSA) and of class B organ identity genes (GLOBOSA) occur before changes in the PLE expression pattern. We propose that STY/FIS are hierarchically high-ranking genes that control cadastral component(s) of the A-function. SQUAMOSA as a potential target of this control is discussed. Retarded growth of second whorl organs, subdivision of third whorl primordia and the failure to initiate them in sty/fis mutants may be mediated by the FIMBRIATA gene.

scholarly journals SUPERMAN, a regulator of floral homeotic genes in Arabidopsis

Development ◽  
1992 ◽  
Vol 114 (3) ◽  
pp. 599-615 ◽  
Author(s):  
J.L. Bowman ◽  
H. Sakai ◽  
T. Jack ◽  
D. Weigel ◽  
U. Mayer ◽  
...  
Keyword(s):  
Gene Product ◽  
Expression Patterns ◽  
Floral Organ ◽  
Homeotic Genes ◽  
Wild Type ◽  
Floral Homeotic Genes ◽  
Mature Flower ◽  
Organ Identity ◽  
Superman Gene ◽  
Floral Homeotic

We describe a locus, SUPERMAN, mutations in which result in extra stamens developing at the expense of the central carpels in the Arabidopsis thaliana flower. The development of superman flowers, from initial primordium to mature flower, is described by scanning electron microscopy. The development of doubly and triply mutant strains, constructed with superman alleles and previously identified homeotic mutations that cause alterations in floral organ identity, is also described. Essentially additive phenotypes are observed in superman agamous and superman apetala2 double mutants. The epistatic relationships observed between either apetala3 or pistillata and superman alleles suggest that the SUPERMAN gene product could be a regulator of these floral homeotic genes. To test this, the expression patterns of AGAMOUS and APETALA3 were examined in superman flowers. In wild-type flowers, APETALA3 expression is restricted to the second and third whorls where it is required for the specification of petals and stamens. In contrast, in superman flowers, APETALA3 expression expands to include most of the cells that would normally constitute the fourth whorl. This ectopic APETALA3 expression is proposed to be one of the causes of the development of the extra stamens in superman flowers. The spatial pattern of AGAMOUS expression remains unaltered in superman flowers as compared to wild-type flowers. Taken together these data indicate that one of the functions of the wild-type SUPERMAN gene product is to negatively regulate APETALA3 in the fourth whorl of the flower. In addition, superman mutants exhibit a loss of determinacy of the floral meristem, an effect that appears to be mediated by the APETALA3 and PISTILLATA gene products.

scholarly journals Multiple requirements for the receptor serine/threonine kinase thick veins reveal novel functions of TGF beta homologs during Drosophila embryogenesis

Development ◽  
1994 ◽  
Vol 120 (11) ◽  
pp. 3105-3117 ◽  
Author(s):  
M. Affolter ◽  
D. Nellen ◽  
U. Nussbaumer ◽  
K. Basler
Keyword(s):  
Cell Communication ◽  
Cell Types ◽  
Dorsal Closure ◽  
Homeotic Genes ◽  
Embryonic Cells ◽  
Tgf Beta ◽  
Loss Of Function ◽  
Surface Receptors ◽  
Visceral Mesoderm ◽  
Distinct Cell

Differentiation of distinct cell types at specific locations within a developing organism depends largely on the ability of cells to communicate. A major class of signalling proteins implicated in cell to cell communication is represented by members of the TGF beta superfamily. A corresponding class of transmembrane serine/threonine kinases has recently been discovered that act as cell surface receptors for ligands of the TGF beta superfamily. The product of the Drosophila gene decapentaplegic (dpp) encodes a TGF beta homolog that plays multiple roles during embryogenesis and the development of imaginal discs. Here we describe the complex expression pattern of thick veins (tkv), which encodes a receptor for dpp. We make use of tkv loss-of-function mutations to examine the consequences of the failure of embryonic cells to respond to dpp and/or other TGF beta homologs. We find that while maternal tkv product allows largely normal dorsoventral pattering of the embryo, zygotic tkv activity is indispensable for dorsal closure of the embryo after germ band retraction. Furthermore, tkv activity is crucial for patterning the visceral mesoderm; in the absence of functional tkv gene product, visceral mesoderm parasegment 7 cells fail to express Ultrabithorax, but instead accumulate Antennapedia protein. The tkv receptor is therefore involved in delimiting the expression domains of homeotic genes in the visceral mesoderm. Interestingly, tkv mutants fail to establish a proper tracheal network. Tracheal braches formed by cells migrating in dorsal or ventral directions are absent in tkv mutants. The requirements for tkv in dorsal closure, visceral mesoderm and trachea development assign novel functions to dpp or a closely related member of the TGF beta superfamily.

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