The rough sheath2 gene negatively regulates homeobox gene expression during maize leaf development

Development ◽  
1998 ◽  
Vol 125 (15) ◽  
pp. 2857-2865 ◽  
Author(s):  
R. Schneeberger ◽  
M. Tsiantis ◽  
M. Freeling ◽  
J.A. Langdale
Keyword(s):  
Gene Expression ◽  
Cell Fate ◽  
Higher Plants ◽  
Leaf Shape ◽  
Ectopic Expression ◽  
Homeobox Gene ◽  
Current Evidence ◽  
Leaf Cell ◽  
Knox Gene ◽  
Knox Genes

Leaves of higher plants are produced in a sequential manner through the differentiation of cells that are derived from the shoot apical meristem. Current evidence suggests that this transition from meristematic to leaf cell fate requires the down-regulation of knotted1-like homeobox (knox) gene expression. If knox gene expression is not repressed, overall leaf shape and cellular differentiation within the leaf are perturbed. In order to identify genes that are required for the aquisition of leaf cell fates, we have genetically screened for recessive mutations that confer phenotypes similar to dominant mutations (e.g. Knotted1 and Rough sheath1) that result in the ectopic expression of class I knox genes. Independently derived mutations at the rough sheath2 (rs2) locus condition a range of pleiotropic leaf, node and internode phenotypes that are sensitive to genetic background and environment. Phenotypes include dwarfism, leaf twisting, disorganized differentiation of the blade-sheath boundary, aberrant vascular patterning and the generation of semi-bladeless leaves. knox genes are initially repressed in rs2 mutants as leaf founder cells are recruited in the meristem. However, this repression is often incomplete and is not maintained as the leaf progresses through developement. Expression studies indicate that three knox genes are ectopically or over-expressed in developing primordia and in mature leaves. We therefore propose that the rs2 gene product acts to repress knox gene expression (either directly or indirectly) and that rs2 gene action is essential for the elaboration of normal leaf morphology.

SEMAPHORE1 functions during the regulation of ancestrally duplicated knox genes and polar auxin transport in maize

Development ◽  
2002 ◽  
Vol 129 (11) ◽  
pp. 2663-2673 ◽  
Author(s):  
Michael J. Scanlon ◽  
David C. Henderson ◽  
Brad Bernstein
Keyword(s):  
Gene Expression ◽  
Cell Fate ◽  
Auxin Transport ◽  
Lateral Roots ◽  
Ectopic Expression ◽  
Polar Auxin Transport ◽  
Knox Gene ◽  
Endosperm Tissue ◽  
Knox Genes ◽  
Class 1

The expression of class 1 knotted1-like homeobox (knox) genes affects numerous plant developmental processes, including cell-fate acquisition, lateral organ initiation, and maintenance of shoot apical meristems. The SEMAPHORE1 gene product is required for the negative regulation of a subset of maize knox genes, the duplicated loci rough sheath 1 and gnarley1 (knox4). Recessive mutations in semaphore1 result in the ectopic expression of knox genes in leaf and endosperm tissue. Genetic analyses suggest that SEMAPHORE1 may regulate knox gene expression in a different developmental pathway than ROUGH SHEATH2, the first-identified regulator of knox gene expression in maize. Mutations at semaphore1 are pleiotropic, disrupting specific domains of the shoot. However, unlike previously described mutations that cause ectopic knox gene expression, semaphore1 mutations affect development of the embryo, endosperm, lateral roots, and pollen. Moreover, polar transport of the phytohormone auxin is significantly reduced in semaphore1 mutant shoots. The data suggest that many of the pleiotropic semaphore1 phenotypes result from defective polar auxin transport (PAT) in sem1 mutant shoots, and support models correlating down-regulated knox gene expression and PAT in maize shoots.

Ectopic Expression of the Arabidopsis Transcriptional Activator Athb-1 Alters Leaf Cell Fate in Tobacco

1995 ◽  
Vol 7 (11) ◽  
pp. 1773 ◽  
Author(s):  
Takashi Aoyama ◽  
Chun-Hai Dong ◽  
Yan Wu ◽  
Monica Carabelli ◽  
Giovanna Sessa ◽  
...  
Keyword(s):  
Cell Fate ◽  
Ectopic Expression ◽  
Transcriptional Activator ◽  
Leaf Cell

Identifying targets of the rough homeobox gene of Drosophila: evidence that rhomboid functions in eye development

Development ◽  
1992 ◽  
Vol 116 (2) ◽  
pp. 335-346 ◽  
Author(s):  
M. Freeman ◽  
B.E. Kimmel ◽  
G.M. Rubin
Keyword(s):  
Cell Fate ◽  
Target Genes ◽  
Eye Development ◽  
Expression Patterns ◽  
Ectopic Expression ◽  
Homeobox Gene ◽  
Homeodomain Protein ◽  
Dorsoventral Patterning ◽  
Altered Expression ◽  
Enhancer Trap Lines

In order to identify potential target genes of the rough homeodomain protein, which is known to specify some aspects of the R2/R5 photoreceptor subtype in the Drosophila eye, we have carried out a search for enhancer trap lines whose expression is rough-dependent. We crossed 101 enhancer traps that are expressed in the developing eye into a rough mutant background, and have identified seven lines that have altered expression patterns. One of these putative rough target genes is rhomboid, a gene known to be required for dorsoventral patterning and development of some of the nervous system in the embryo. We have examined the role of rhomboid in eye development and find that, while mutant clones have only a subtle phenotype, ectopic expression of the gene causes the non-neuronal mystery cells to be transformed into photoreceptors. We propose that rhomboid is a part of a partially redundant network of genes that specify photoreceptor cell fate.

A maize chromosome 3 addition line of oat exhibits expression of the maize homeobox gene liguleless3 and alteration of cell fates

Genome ◽  
2000 ◽  
Vol 43 (6) ◽  
pp. 1055-1064 ◽  
Author(s):  
G J Muehlbauer ◽  
O Riera-Lizarazu ◽  
R G Kynast ◽  
D Martin ◽  
R L Phillips ◽  
...  
Keyword(s):  
Cell Fate ◽  
Ectopic Expression ◽  
Homeobox Gene ◽  
Chromosome 3 ◽  
Addition Line ◽  
Addition Lines ◽  
Morphological Examination ◽  
Maize Chromosome ◽  
Chromosome Addition ◽  
Chromosome Addition Lines

Maize chromosome addition lines of oat offer the opportunity to study maize gene expression in oat and the resulting phenotypes. Morphological examination of a maize chromosome 3 addition line of oat showed that this line exhibited several morphological abnormalities including a blade-to-sheath transformation at the midrib region of the leaf, a hook-shaped panicle, and abnormal outgrowth of aerial axillary buds. Dominant mutations in the maize liguleless3 (lg3) homeobox gene result in a blade (distal)-to-sheath (proximal) transformation at the midrib region of the leaf. Ectopic expression of the dominant mutant Lg3 allele is believed to cause the phenotype. Therefore, we suspected that the maize lg3 gene, which is located on maize chromosome 3, was involved in the phenotypes observed in the maize chromosome 3 addition line of oat. Genetic analyses of an oat BC1F2 family segregating for maize chromosome 3 showed that the presence of a stable maize chromosome 3 was required for the expression of these cell fate abnormalities. RNA expression analysis of leaf sheath tissue from oat plants carrying maize chromosome 3 demonstrated that maize LG3 transcripts accumulated in oat, indicating that this expression is associated with the blade-to-sheath transformation, hook-shaped panicle and outgrowth of aerial axillary bud phenotypes. Our results demonstrate that the maize chromosome addition lines of oat are useful genetic stocks to study expression of maize genes in oat.Key words: liguleless3, homeobox, oat-maize addition line.

Transgenic lines of Begonia maculata generated by ectopic expression of PttKN1

Biologia ◽  
2011 ◽  
Vol 66 (2) ◽  
Author(s):  
Quan-le Xu ◽  
Jiang-ling Dong ◽  
Nan Gao ◽  
Mei-yu Ruan ◽  
Hai-yan Jia ◽  
...  
Keyword(s):  
Transgenic Plants ◽  
Ectopic Expression ◽  
Class I ◽  
Wild Type Plant ◽  
Wild Type ◽  
Knox Gene ◽  
Knox Genes ◽  
Pttkn1 Gene ◽  
Transgenic Lines ◽  
First Time

AbstractKNOX (KNOTTED1-like homeobox) genes encode homeodomain-containing transcription factors which play crucial roles in meristem maintenance and proper patterning of organ initiation. PttKN1 gene, isolated from the vascular cambium of hybrid aspen (Populus tremula × P. tremuloides), is a member of class I KNOX gene family. In order to understand the roles of PttKN1 gene in meristem activity and morphogenesis as well as to explore the possibility to generate novel ornamental lines via its ectopic expression, it was introduced into the genome of Begonia maculata Raddi by Agrobacterium tumefasciens-mediated gene transformation here. Four types of transgenic plants were observed, namely coral-like (CL) type, ectopic foliole (EF) type, phyllotaxy-irregular (IP) type and cup-shaped (CS) type, which were remarkably different from corresponding wild type and were not also observed in the regenerated plantlets of wild type plant. Among these four types of transgenic plants, the phenotype of coral-like was observed for the first time in the transformants ectopically expressed KNOX genes. The observation of scanning electron microscope (SEM) showed ectopic meristems on the adaxial leaf surface of the transformants. Interestingly, the plantlets with ectopic foliole could generate new ectopic folioles from the original ectopic folioles again, and the plants regenerated from the EF-type transformants could also maintain the original morphology. The same specific RT-PCR band of the four types of transgenic plantlets showed that PttKN1 was ectopically expressed. All these data demonstrated that the ectopic expression of PttKN1 caused a series of alterations in morphology which provided possibilities producing novel ornamental lines and that PttKN1 played important roles in meristem initiation, maintenance and organogenesis events as other class I KNOX genes.

Mechanisms that control knox gene expression in the Arabidopsis shoot

Development ◽  
2000 ◽  
Vol 127 (24) ◽  
pp. 5523-5532 ◽  
Author(s):  
N. Ori ◽  
Y. Eshed ◽  
G. Chuck ◽  
J.L. Bowman ◽  
S. Hake
Keyword(s):  
Gene Expression ◽  
Knox Gene ◽  
Phenotypic Characteristics ◽  
Knox Genes ◽  
Meristem Maintenance ◽  
Leaf Differentiation ◽  
Shoot Meristems

Knotted1-like homeobox (knox) genes are expressed in specific patterns within shoot meristems and play an important role in meristem maintenance. Misexpression of the knox genes, KNAT1 or KNAT2, in Arabidopsis produces a variety of phenotypes, including lobed leaves and ectopic stipules and meristems in the sinus, the region between lobes. We sought to determine the mechanisms that control knox gene expression in the shoot by examining recessive mutants that share phenotypic characteristics with 35S::KNAT1 plants. Double mutants of serrate (se) with either asymmetric1 (as1) or asymmetric2 (as2) showed lobed leaves, ectopic stipules in the sinuses and defects in the timely elongation of sepals, petals and stamens, similar to 35S::KNAT1 plants. Ectopic stipules and in rare cases, ectopic meristems, were detected in the sinuses on plants that were mutant for pickle and either as1 or as2. KNAT1 and KNAT2 were misexpressed in the leaves and flowers of single as1 and as2 mutants and in the sinuses of leaves of the different double mutants, but not in se or pickle single mutants. These results suggest that AS1 and AS2 promote leaf differentiation through repression of knox expression in leaves, and that SE and PKL globally restrict the competence to respond to genes that promote morphogenesis.

The zinc finger proteins Pannier and GATA4 function as cardiogenic factors in Drosophila

Development ◽  
1999 ◽  
Vol 126 (24) ◽  
pp. 5679-5688 ◽  
Author(s):  
K. Gajewski ◽  
N. Fossett ◽  
J.D. Molkentin ◽  
R.A. Schulz
Keyword(s):  
Gene Expression ◽  
Cell Fate ◽  
Zinc Finger ◽  
Heart Development ◽  
Ectopic Expression ◽  
Cell Formation ◽  
Homeodomain Protein ◽  
Gata Factor ◽  
Cardiac Gene Expression ◽  
Cardiac Gene

The regulation of cardiac gene expression by GATA zinc finger transcription factors is well documented in vertebrates. However, genetic studies in mice have failed to demonstrate a function for these proteins in cardiomyocyte specification. In Drosophila, the existence of a cardiogenic GATA factor has been implicated through the analysis of a cardial cell enhancer of the muscle differentiation gene D-mef2. We show that the GATA gene pannier is expressed in the dorsal mesoderm and required for cardial cell formation while repressing a pericardial cell fate. Ectopic expression of Pannier results in cardial cell overproduction, while co-expression of Pannier and the homeodomain protein Tinman synergistically activate cardiac gene expression and induce cardial cells. The related GATA4 protein of mice likewise functions as a cardiogenic factor in Drosophila, demonstrating an evolutionarily conserved function between Pannier and GATA4 in heart development.

A role for the rice homeobox gene Oshox1 in provascular cell fate commitment

Development ◽  
2000 ◽  
Vol 127 (17) ◽  
pp. 3655-3669 ◽  
Author(s):  
E. Scarpella ◽  
S. Rueb ◽  
K.J. Boot ◽  
J.H. Hoge ◽  
A.H. Meijer
Keyword(s):  
Cell Fate ◽  
Leucine Zipper ◽  
Ectopic Expression ◽  
Homeobox Gene ◽  
Vascular Differentiation ◽  
Developmental Potential ◽  
Plant Body ◽  
Procambial Cell ◽  
Vascular Element ◽  
Molecular Nature

The vascular tissues of plants form a network of interconnected cell files throughout the plant body. The transition from a genetically totipotent meristematic precursor to different stages of a committed procambial cell, and its subsequent differentiation into a mature vascular element, involves developmental events whose molecular nature is still mostly unknown. The rice protein Oshox1 is a member of the homeodomain leucine zipper family of transcription factors. Here we show that the strikingly precise onset of Oshox1 gene expression marks critical, early stages of provascular ontogenesis in which the developmental fate of procambial cells is specified but not yet stably determined. This suggests that the Oshox1 gene may be involved in the establishment of the conditions required to restrict the developmental potential of procambial cells. In support of this hypothesis, ectopic expression of Oshox1 in provascular cells that normally do not yet express this gene results in anticipation of procambial cell fate commitment, eventually culminating in premature vascular differentiation. Oshox1 represents the first example of a transcription factor whose function can be linked to specification events mediating provascular cell fate commitment.

The role of the msh homeobox gene during Drosophila neurogenesis: implication for the dorsoventral specification of the neuroectoderm

Development ◽  
1997 ◽  
Vol 124 (16) ◽  
pp. 3099-3109 ◽  
Author(s):  
T. Isshiki ◽  
M. Takeichi ◽  
A. Nose
Keyword(s):  
Cell Fate ◽  
Neural Development ◽  
Ectopic Expression ◽  
Homeobox Gene ◽  
Loss Of Function ◽  
Spinal Cord Development ◽  
Dorsal Portion ◽  
Msx Genes

Development of the Drosophila central nervous system begins with the delamination of neural and glial precursors, called neuroblasts, from the neuroectoderm. An early and important step in the generation of neural diversity is the specification of individual neuroblasts according to their position. In this study, we describe the genetic analysis of the msh gene which is likely to play a role in this process. The msh/Msx genes are one of the most highly conserved families of homeobox genes. During vertebrate spinal cord development, Msx genes (Msx1-3) are regionally expressed in the dorsal portion of the developing neuroectoderm. Similarly in Drosophila, msh is expressed in two longitudinal bands that correspond to the dorsal half of the neuroectoderm, and subsequently in many dorsal neuroblasts and their progeny. We showed that Drosophila msh loss-of-function mutations led to cell fate alterations of neuroblasts formed in the dorsal aspect of the neuroectoderm, including a possible dorsal-to-ventral fate switch. Conversely, ectopic expression of msh in the entire neuroectoderm severely disrupted the proper development of the midline and ventral neuroblasts. The results provide the first in vivo evidence for the role of the msh/Msx genes in neural development, and support the notion that they may perform phylogenetically conserved functions in the dorsoventral patterning of the neuroectoderm.

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