Cell cycle regulates cell type in the<i>Arabidopsis</i>sepal

Roeder, Adrienne; Cunha, Alexandre; Ohno, Carolyn; Meyerowitz, Elliot M.

doi:10.1242/dev.082925

Cited by 102 publications

(145 citation statements)

References 57 publications

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“…Sixteen HD-ZIP IV proteins have been identified in Arabidopsis, including MERISTEM LAYER1 (ATML1), GLABRA2 (GL2), ANTHOCYANINLESS2 (ANL2) and PROTODERMAL FACTOR2 (PDF2) (Nakamura et al, 2006). HD-ZIP IV/HDG genes are expressed in the L1 layer throughout the plant, where they function to specify epidermis identity and control development of its associated structures, such as trichomes, stomata or giant cells (Abe et al, 2003;Nakamura et al, 2006;Roeder et al, 2012;Peterson et al, 2013;Takada et al, 2013). Our results show that BBM and HDG proteins have antagonistic functions, with BBM stimulating cell proliferation and HDGs stimulating cell differentiation.…”

Section: Introductionmentioning

confidence: 63%

“…The elongated cells found in HDG1 overexpression lines are reminiscent of giant cells, which are differentiated, endoreduplicated cells found in the sepal epidermis (Roeder et al, 2012). Similarly elongated cells are found along the margin of cotyledons and leaves ( Fig.…”

Section: Hdg1 Overexpression Promotes Giant Cell Identitymentioning

confidence: 82%

“…3O,P), reminiscent of the cells found on sepals and leaf margins (Fig. 3J) (Roeder et al, 2012), rather than the puzzle-shaped cells found in wild-type leaves (Fig. 3J).…”

Section: Overexpression Of Hdg Genes Induces Meristem Arrest and Leafmentioning

confidence: 86%

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AIL and HDG proteins act antagonistically to control cell proliferation

et al. 2015

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AINTEGUMENTA-LIKE (AIL) transcription factors are key regulators of cell proliferation and meristem identity. Although AIL functions have been well described, the direct signalling components of this pathway are largely unknown. We show that BABY BOOM (BBM) and other AIL proteins physically interact with multiple members of the L1-expressed HOMEODOMAIN GLABROUS (HDG) transcription factor family, including HDG1, HDG11 and HDG12. Overexpression of HDG1, HDG11 and HDG12 restricts growth due to root and shoot meristem arrest, which is associated with reduced expression of genes involved in meristem development and cell proliferation pathways, whereas downregulation of multiple HDG genes promotes cell overproliferation. These results suggest a role for HDG proteins in promoting cell differentiation. We also reveal a transcriptional network in which BBM and HDG1 regulate several common target genes, and where BBM/AIL and HDG regulate the expression of each other. Taken together, these results suggest opposite roles for AIL and HDG proteins, with AILs promoting cell proliferation and HDGs stimulating cell differentiation, and that these functions are mediated at both the protein-protein interaction and transcriptional level.

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Section: Introductionmentioning

confidence: 63%

Section: Hdg1 Overexpression Promotes Giant Cell Identitymentioning

confidence: 82%

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AIL and HDG proteins act antagonistically to control cell proliferation

et al. 2015

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“…Mutants used in the study were in the Col background. The following mutants and reporter lines have been reported previously: TMMpro::GUS-GFP (Nadeau and Sack, 2002), TMMpro::GUS (Shpak et al, 2005), EPF2pro::erGFP (Hara et al, 2009), AtML1pro::GUS (Uchida et al, 2012), SPCHpro::GUS and E994 (Pillitteri et al, 2007), GL2pro::GUS (Masucci et al, 1996) and At5g17710pro::nuc-3xVENUS (Roeder et al, 2012). T-DNA insertion lines: hdg2-2 (SALK_127828C); hdg2-3 (SALK_138646C); hdg2-4 (SALK_120064); atml1-3 (SALK_128172); atml1-4 (SALK_033408) and pdf2-2 (SALK_109425C) were obtained from the Arabidopsis Biological Resource Center (ABRC), and loss or disruption of their transcripts was confirmed (supplementary material Fig.…”

Section: Plant Materials and Growth Conditionsmentioning

confidence: 99%

“…3E). We therefore used an endoreduplicating epidermal cell marker (At5g17710pro::nuc-3xVENUS) (Roeder et al, 2012) to address this issue (Fig. 3G-I).…”

Section: Hdg2 Overexpression Confers Differentiation Of Ectopic Stomamentioning

confidence: 99%

Arabidopsis homeodomain-leucine zipper IV proteins promote stomatal development and ectopically induce stomata beyond the epidermis

et al. 2013

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SUMMARYThe shoot epidermis of land plants serves as a crucial interface between plants and the atmosphere: pavement cells protect plants from desiccation and other environmental stresses, while stomata facilitate gas exchange and transpiration. Advances have been made in our understanding of stomatal patterning and differentiation, and a set of 'master regulatory' transcription factors of stomatal development have been identified. However, they are limited to specifying stomatal differentiation within the epidermis. Here, we report the identification of an Arabidopsis homeodomain-leucine zipper IV (HD-ZIP IV) protein, HOMEODOMAIN GLABROUS2 (HDG2), as a key epidermal component promoting stomatal differentiation. HDG2 is highly enriched in meristemoids, which are transient-amplifying populations of stomatal-cell lineages. Ectopic expression of HDG2 confers differentiation of stomata in internal mesophyll tissues and occasional multiple epidermal layers. Conversely, a loss-of-function hdg2 mutation delays stomatal differentiation and, rarely but consistently, results in aberrant stomata. A closely related HD-ZIP IV gene, Arabidopsis thaliana MERISTEM LAYER1 (AtML1), shares overlapping function with HDG2: AtML1 overexpression also triggers ectopic stomatal differentiation in the mesophyll layer and atml1 mutation enhances the stomatal differentiation defects of hdg2. Consistently, HDG2 and AtML1 bind the same DNA elements, and activate transcription in yeast. Furthermore, HDG2 transactivates expression of genes that regulate stomatal development in planta. Our study highlights the similarities and uniqueness of these two HD-ZIP IV genes in the specification of protodermal identity and stomatal differentiation beyond predetermined tissue layers.

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Sepals

Roeder

2023

Encyclopedia of Life Sciences

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Sepals are the outermost organs of a flower. They are sterile and generally green leaf‐like organs that surround and protect the developing reproductive structures inside the bud before the flower blooms. The sepals are the first organs initiated from the floral meristem and quickly grow to cover the floral meristem and initiating organ primordia. The sepals and petals in the flower interact with the environment by both attracting pollinators as well as defending against predators and abiotic factors such as the weather. Sepal organ identity is specified by the A function in the ABC model. Arabidopsis sepals are a model system for investigating morphogenesis (development of organ size and shape) and patterning (differentiation of specialised cell types such as giant cells). Current and future research on the development of sepals is leading to a better understanding of floral organ formation as well as underlying principles of cell division and growth. Key Concepts Sepals are the outermost floral organs, which are typically green leaf‐like organs that enclose and protect the developing flower bud before blooming. Sepals are thought to have evolved from leaves. Sepal organ identity is specified by A and E function in the ABC model of floral organ identity, and A function is specified by AP1/CAL/FUL clade MADS domain transcription factors, AP2 domain family transcription factors and microRNAs. The sepal is a commonly studied in Arabidopsis to discover fundamental principles of morphogenesis, such as how plant organs grow to reach the right size and shape. Arabidopsis sepals are the first floral organs to initiate on the flanks of the floral meristem where they quickly grow to cover and protect the developing reproductive organs, keep the bud closed until blooming and senesce and abscise after the fruit is fertilised. A scattered pattern of giant cells forms in between smaller cells in the outer epidermis of Arabidopsis sepals. The Arabidopsis thaliana MERISTEM LAYER1 (ATML1) transcription factor concentration fluctuates in epidermal cells of the developing sepal; if ATML1 reaches a high concentration during G2 phase of the cell cycle, the cell becomes giant. Giant cells become enlarged through endoreplication (also known as endoreduplication), during which a cell replicates its DNA and grows without division, becoming highly enlarged and polyploid. Sepal size and shape are highly reproducible; synchronous timing of both the initiation of sepal primordia and their maturation and cessation of growth are required for all four sepals in the Arabidopsis flower to maintain the same size to enclose the flower bud. The growth and division of sepal cells are highly variable, and gene expression is stochastic; however, sepals maintain robust size and shape through spatiotemporal averaging of growth variability and suppression of gene expression noise by the Paf1C complex.

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Cell cycle regulates cell type in theArabidopsissepal

Cited by 102 publications

References 57 publications

AIL and HDG proteins act antagonistically to control cell proliferation

AIL and HDG proteins act antagonistically to control cell proliferation

Arabidopsis homeodomain-leucine zipper IV proteins promote stomatal development and ectopically induce stomata beyond the epidermis

Sepals

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