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Gambino G, Minuto M, Boccacci P, Perrone I, Vallania R, Gribaudo I. Characterization of expression dynamics of WOX homeodomain transcription factors during somatic embryogenesis in Vitis vinifera. JOURNAL OF EXPERIMENTAL BOTANY 2011; 62:1089-1101. [PMID: 21127025 DOI: 10.1093/jxb/erq349] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Different cultivars of Vitis vinifera vary in their potential to form embryogenic tissues. The WUSCHEL (WUS)-related homeobox (WOX) genes have been shown to play an important role in coordinating the gene transcription involved in the early phases of embryogenesis. The expression dynamics of 12 VvWOX genes present in the V. vinifera genome in embryogenic and other tissues of 'Chardonnay' were analysed. In order to understand the influence of WOX genes on the somatic embryogenic process, their expression profiles were compared in two cultivars of V. vinifera ('Chardonnay' and 'Cabernet Sauvignon') that show different aptitudes for embryogenesis. The expression of all VvWOX genes was influenced by culture conditions. VvWOX2 and VvWOX9 were the principal WOX genes expressed during the somatic embryogenesis process, and the low aptitude for embryogenesis of 'Cabernet Sauvignon' was generally correlated with the low expression levels of these VvWOX genes. VvWOX3 and VvWOX11 were strongly activated in correspondence to torpedo and cotyledonary stages of somatic embryos, with low expression in the earlier developmental stages (pre-embryogenic masses and globular embryos) and during embryo germination. VvWOX genes appeared to be key regulators of somatic embryogenesis in grapevine, and the regulation of these genes during early phases of somatic embryogenesis differed between the two cultivars of the same species.
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Affiliation(s)
- Giorgio Gambino
- Plant Virology Institute, National Research Council, UOS Grugliasco, Via L. da Vinci 44, I-10095 Grugliasco, TO, Italy.
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152
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Palovaara J, Hallberg H, Stasolla C, Hakman I. Comparative expression pattern analysis of WUSCHEL-related homeobox 2 (WOX2) and WOX8/9 in developing seeds and somatic embryos of the gymnosperm Picea abies. THE NEW PHYTOLOGIST 2010; 188:122-35. [PMID: 20561212 DOI: 10.1111/j.1469-8137.2010.03336.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
• In seed plants, current knowledge concerning embryonic pattern formation by polar auxin transport (PAT) and WUSCHEL-related homeobox (WOX) gene activity is primarily derived from studies on angiosperms, while less is known about these processes in gymnosperms. In view of the differences in their embryogeny, and the fact that somatic embryogenesis is used for mass propagation of conifers, a better understanding of embryo development is vital. • The expression patterns of PaWOX2 and PaWOX8/9 were followed with quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and in situ hybridization (ISH) during seed and somatic embryo development in Norway spruce (Picea abies), and in somatic embryos treated with the PAT inhibitor N-1-naphthylphthalamic acid (NPA). • Both PaWOX2 and PaWOX8/9 were highly expressed at the early growth stages of zygotic and somatic embryos, and shared a similar expression pattern over the entire embryo. At later embryo stages, high expression of PaWOX8/9 became restricted to cotyledon primordia, epidermis, procambium and root apical meristem (RAM), which became most evident in NPA-treated somatic embryos, while expression of PaWOX2 was much lower. • Our results suggest an ancestral role of WOX in seed plant embryo development, and strengthen the proposed connection between PAT, PIN-FORMED (PIN) and WOX in the regulation of embryo patterning in seed plants.
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Affiliation(s)
- Joakim Palovaara
- School of Natural Sciences, Linnaeus University, SE-391 82 Kalmar, Sweden
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153
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Hirakawa Y, Kondo Y, Fukuda H. TDIF peptide signaling regulates vascular stem cell proliferation via the WOX4 homeobox gene in Arabidopsis. THE PLANT CELL 2010; 22:2618-29. [PMID: 20729381 PMCID: PMC2947162 DOI: 10.1105/tpc.110.076083] [Citation(s) in RCA: 363] [Impact Index Per Article: 25.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2010] [Revised: 07/02/2010] [Accepted: 08/04/2010] [Indexed: 05/18/2023]
Abstract
The indeterminate nature of plant growth and development depends on the stem cell system found in meristems. The Arabidopsis thaliana vascular meristem includes procambium and cambium. In these tissues, cell-cell signaling, mediated by a ligand-receptor pair made of the TDIF (for tracheary element differentiation inhibitory factor) peptide and the TDR/PXY (for TDIF RECEPTOR/ PHLOEM INTERCALATED WITH XYLEM) membrane protein kinase, promotes proliferation of procambial cells and suppresses their xylem differentiation. Here, we report that a WUSCHEL-related HOMEOBOX gene, WOX4, is a key target of the TDIF signaling pathway. WOX4 is expressed preferentially in the procambium and cambium, and its expression level was upregulated upon application of TDIF in a TDR-dependent manner. Genetic analyses showed that WOX4 is required for promoting the proliferation of procambial/cambial stem cells but not for repressing their commitment to xylem differentiation in response to the TDIF signal. Thus, at least two intracellular signaling pathways that diverge after TDIF recognition by TDR might regulate independently the behavior of vascular stem cells. Detailed observations in loss-of-function mutants revealed that TDIF-TDR-WOX4 signaling plays a crucial role in the maintenance of the vascular meristem organization during secondary growth.
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Affiliation(s)
| | | | - Hiroo Fukuda
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
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154
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Ji J, Shimizu R, Sinha N, Scanlon MJ. Analyses of WOX4 transgenics provide further evidence for the evolution of the WOX gene family during the regulation of diverse stem cell functions. PLANT SIGNALING & BEHAVIOR 2010; 5:916-20. [PMID: 20495368 PMCID: PMC3014546 DOI: 10.4161/psb.5.7.12104] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
The WOX (WUSCHEL-related homeobox) gene family of Arabidopsis comprises fifteen plant-specific transcriptional factors that play important development roles. Genetic, phylogenetic, and genomic analyses suggest that WOX genes generally act non-autonomously to organize stem-cell and initial-cell populations within plant meristems and organ anlagen. Previous cross-complementation analyses indicate that the functional diversification of distinct WOX paralogs may be explained largely by promoter evolution, although paralog-specific protein::protein interactions are also implicated. A recent report described WOX4 function during development of the procambium, which comprises the meristematic tissues of the plant vasculature. Here we show that WOX4 fails to complement PRS1/WOX3 function, when driven from the PRS1/WOX3 native promoter. These data suggest that WOX4 identifies different DNA targets and/or interacting proteins during development of the vasculature procambium than does PRS1/WOX3 during the specification of lateral organ initial cells. The identification of super-compound leaf phenotypes induced by overexpression of the SlWOX4 ortholog in tomato suggests a functional link between vascular patterning and leaf complexity.
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Affiliation(s)
- Jiabing Ji
- Plant Biology Department, University of Georgia, Athens, GA, USA
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155
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Yamaguchi T, Yano S, Tsukaya H. Genetic framework for flattened leaf blade formation in unifacial leaves of Juncus prismatocarpus. THE PLANT CELL 2010; 22:2141-55. [PMID: 20647346 PMCID: PMC2929117 DOI: 10.1105/tpc.110.076927] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2010] [Revised: 06/25/2010] [Accepted: 07/06/2010] [Indexed: 05/19/2023]
Abstract
Angiosperm leaves generally develop as bifacial structures with distinct adaxial and abaxial identities. However, several monocot species, such as iris and leek, develop unifacial leaves, in which leaf blades have only abaxial identity. In bifacial leaves, adaxial-abaxial polarity is required for leaf blade flattening, whereas many unifacial leaves become flattened despite their leaf blades being abaxialized. Here, we investigate the mechanisms underlying the development and evolution of flattened leaf blades in unifacial leaves. We demonstrate that the unifacial leaf blade is abaxialized at the gene expression level and that an ortholog of the DROOPING LEAF (DL) gene may promote flattening of the unifacial leaf blade. In two closely related Juncus species, Juncus prismatocarpus, which has flattened unifacial leaves, and Juncus wallichianus, which has cylindrical unifacial leaves, DL expression levels and patterns correlate with the degree of laminar outgrowth. Genetic and expression studies using interspecific hybrids of the two species reveal that the DL locus from J. prismatocarpus flattens the unifacial leaf blade and expresses higher amounts of DL transcript than does that from J. wallichianus. We also show that leaf blade flattening is a trigger for central-marginal leaf polarity differentiation. We suggest that flattened unifacial leaf blades may have evolved via the recruitment of DL function, which plays a similar cellular but distinct phenotypic role in monocot bifacial leaves.
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156
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Sarojam R, Sappl PG, Goldshmidt A, Efroni I, Floyd SK, Eshed Y, Bowman JL. Differentiating Arabidopsis shoots from leaves by combined YABBY activities. THE PLANT CELL 2010; 22:2113-30. [PMID: 20628155 PMCID: PMC2929102 DOI: 10.1105/tpc.110.075853] [Citation(s) in RCA: 191] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2010] [Revised: 04/15/2010] [Accepted: 06/17/2010] [Indexed: 05/18/2023]
Abstract
In seed plants, leaves are born on radial shoots, but unlike shoots, they are determinate dorsiventral organs made of flat lamina. YABBY genes are found only in seed plants and in all cases studied are expressed primarily in lateral organs and in a polar manner. Despite their simple expression, Arabidopsis thaliana plants lacking all YABBY gene activities have a wide range of morphological defects in all lateral organs as well as the shoot apical meristem (SAM). Here, we show that leaves lacking all YABBY activities are initiated as dorsiventral appendages but fail to properly activate lamina programs. In particular, the activation of most CINCINNATA-class TCP genes does not commence, SAM-specific programs are reactivated, and a marginal leaf domain is not established. Altered distribution of auxin signaling and the auxin efflux carrier PIN1, highly reduced venation, initiation of multiple cotyledons, and gradual loss of the SAM accompany these defects. We suggest that YABBY functions were recruited to mold modified shoot systems into flat plant appendages by translating organ polarity into lamina-specific programs that include marginal auxin flow and activation of a maturation schedule directing determinate growth.
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Affiliation(s)
- Rajani Sarojam
- Section of Plant Biology, University of California, Davis, California 95616
| | - Pia G. Sappl
- School of Biological Sciences, Monash University, Melbourne, Victoria 3800, Australia
| | - Alexander Goldshmidt
- Department of Plant Sciences, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Idan Efroni
- Department of Plant Sciences, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Sandra K. Floyd
- School of Biological Sciences, Monash University, Melbourne, Victoria 3800, Australia
| | - Yuval Eshed
- Department of Plant Sciences, Weizmann Institute of Science, Rehovot 76100, Israel
| | - John L. Bowman
- Section of Plant Biology, University of California, Davis, California 95616
- School of Biological Sciences, Monash University, Melbourne, Victoria 3800, Australia
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157
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Ji J, Strable J, Shimizu R, Koenig D, Sinha N, Scanlon MJ. WOX4 promotes procambial development. PLANT PHYSIOLOGY 2010; 152:1346-56. [PMID: 20044450 PMCID: PMC2832261 DOI: 10.1104/pp.109.149641] [Citation(s) in RCA: 147] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2009] [Accepted: 12/21/2009] [Indexed: 05/20/2023]
Abstract
Plant shoot organs arise from initial cells that are recruited from meristematic tissues. Previous studies have shown that members of the WUSCHEL-related HOMEOBOX (WOX) gene family function to organize various initial cell populations during plant development. The function of the WOX4 gene is previously undescribed in any plant species. Comparative analyses of WOX4 transcription and function are presented in Arabidopsis (Arabidopsis thaliana), a simple-leafed plant with collateral vasculature, and in tomato (Solanum lycopersicum), a dissected-leafed species with bicollateral venation. WOX4 is transcribed in the developing vascular bundles of root and shoot lateral organs in both Arabidopsis and tomato. RNA interference-induced down-regulation of WOX4 in Arabidopsis generated small plants whose vascular bundles accumulated undifferentiated ground tissue and exhibited severe reductions in differentiated xylem and phloem. In situ hybridization analyses of Atwox4-RNA interference plants revealed delayed and reduced expression of both the phloem developmental marker ALTERED PHLOEM1 and HOMEOBOX GENE8, a marker of the vascular procambium. Overexpression of SlWOX4 correlated with overproliferation of xylem and phloem in transgenic tomato seedlings. The cumulative data suggest that the conserved WOX4 function is to promote differentiation and/or maintenance of the vascular procambium, the initial cells of the developing vasculature.
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Affiliation(s)
- Jiabing Ji
- Plant Biology Department, University of Georgia, Athens, Georgia 30602
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158
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Abstract
Most leaves are dorsiventrally flattened and develop clearly defined upper and lower surfaces. Light capturing is the specialization of the adaxial or upper surface and the abaxial or lower surface is specialized for gas exchange (Fig. 5.1). This division into adaxial and abaxial domains is also key for the outgrowth of the leaf blade or lamina, which occurs along the boundary between the upper and lower sides. How this polarity is set up is not clear but genetic analysis in a range of species suggests that several highly conserved interlocking pathways are involved. Positional information from the meristem is reinforced by signaling through the epidermal layer as the meristem grows away from the leaf primordium. Opposing ta-siRNA and miRNA gradients help refine distinct adaxial and abaxial sides, and mutual inhibition between the genes expressed on each side stabilizes the boundary. In this review we consider how recent work in a range of species is clarifying our understanding of these processes.
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159
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Abstract
The plant-specific WOX family of homeobox proteins have key functions in plant development.
The WOX genes form a plant-specific subclade of the eukaryotic homeobox transcription factor superfamily, which is characterized by the presence of a conserved DNA-binding homeodomain. The analysis of WOX gene expression and function shows that WOX family members fulfill specialized functions in key developmental processes in plants, such as embryonic patterning, stem-cell maintenance and organ formation. These functions can be related to either promotion of cell division activity and/or prevention of premature cell differentiation. The phylogenetic tree of the plant WOX proteins can be divided into three clades, termed the WUS, intermediate and ancient clade. WOX proteins of the WUS clade appear to some extent able to functionally complement other members. The specific function of individual WOX-family proteins is most probably determined by their spatiotemporal expression pattern and probably also by their interaction with other proteins, which may repress their transcriptional activity. The prototypic WOX-family member WUS has recently been shown to act as a bifunctional transcription factor, functioning as repressor in stem-cell regulation and as activator in floral patterning. Past research has mainly focused on part of the WOX protein family in some model flowering plants, such as Arabidopsis thaliana (thale cress) or Oryza sativa (rice). Future research, including so-far neglected clades and non-flowering plants, is expected to reveal how these master switches of plant differentiation and embryonic patterning evolved and how they fulfill their function.
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Affiliation(s)
- Eric van der Graaff
- Institute of Biology III, Faculty of Biology, University of Freiburg, Schänzlestrasse 1, D-79104 Freiburg, Germany
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