Stomatal development: a plant's perspective on cell polarity, cell fate transitions and intercellular communication
ABSTRACT The plant stomatal lineage manifests features common to many developmental contexts: precursor cells are chosen from an initially equivalent field of cells, undergo asymmetric and self-renewing divisions, communicate among themselves and respond to information from a distance. As we review here, the experimental accessibility of these epidermal lineages, particularly in Arabidopsis, has made stomata a conceptual and technical framework for the study of cell fate, stem cells, and cell polarity in plants.
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ABSTRACT: Stomata are two-celled valves that control epidermal pores whose opening and spacing optimizes shoot-atmosphere gas exchange. Arabidopsis stomatal formation involves at least one asymmetric division and one symmetric division. Stomatal formation and patterning are regulated by the frequency and placement of asymmetric divisions. This model system has already led to significant advances in developmental biology, such as the regulation of cell fate, division, differentiation, and patterning. Over the last 30 years, stomatal development has been found to be controlled by numerous intrinsic genetic and environmental factors. This mini review focuses on the signaling involved in stomatal initiation and in divisions in the cell lineage.Frontiers in Plant Science 06/2014; 5:297. DOI:10.3389/fpls.2014.00297 · 3.64 Impact Factor
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ABSTRACT: The Arabidopsis stoma is a specialized epidermal valve made up of a pair of guard cells around a pore whose aperture controls gas exchange between the shoot and atmosphere. Guard cells (GCs) are produced by a symmetric division of guard mother cells (GMCs). The R2R3-MYB transcription factor FOUR LIPS (FLP) and its paralogue MYB88 restrict the division of a GMC to one. Previously, the upstream regions of several core cell cycle genes were identified as the direct targets of FLP/MYB88, including the B-type cyclin-dependent kinase CDKB1;1 and A2-type cyclin CYCA2;3. Here we show that CDKA;1 is also an immediate direct target of FLP/MYB88 through the binding to cis-regulatory elements in the CDKA;1 promoter region. CDKA;1 activity is required not only for normal GMC divisions but also for the excessive cell overproliferation in flp myb88 mutant GMCs. The impaired defects of GMC division in cdkb1;1 1;2 mutants could be partially rescued by a stage-specific expression of CDKA;1. Although targeted overexpression of CDKA;1 does not affect stomatal development, ectopic expression of the D3-type cyclin CYCD3;2 induces GC subdivision, resulting in a stoma with 3-4 GCs instead of the normal two. Co-overexpression of CDKA;1 with CYCD3;2, but not with CYCA2;3, confers a synergistic effect with respect to GC subdivision. Thus, in addition to a role in stomatal formative asymmetric divisions at early developmental stages, CDKA;1 is needed in triggering GMC symmetric divisions at the late stage of stomatal development. However, timely down-regulation of CDKA;1-CYCD3 activity is required for restriction of GC proliferation.Journal of Experimental Botany 03/2014; 65(9). DOI:10.1093/jxb/eru139 · 5.79 Impact Factor
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ABSTRACT: Functional redundancy arises between gene paralogs as well as non-homologous genes that play a common role at a shared node. The bHLH transcription factor FAMA, along with the paralogous MYB genes, FOUR LIPS (FLP) and MYB88 all ensure that Arabidopsis stomata contain just two guard cells (GCs) by enforcing a single symmetric precursor cell division before stomatal mature. Consistent with this function, FLP and FAMA exhibit the same expression pattern in which both translational GFP fusions emit fluorescence just before and after symmetric division. However, FAMA but not FLP is required to confer GC fate (Ohashi-Ito and Bergmann, 2006). Strikingly, swapping the genes and promoters of the FLP and FAMA genes results in the reciprocal complementation of respective loss of function mutants. Thus, a FLP transgene can restore GC fate to a fama mutant background. FAMA, FLP, and the FLP paralog MYB88 were previously shown to influence higher order functions in stomatal development including maintaining and stabilizing stomatal fate. Here we show that these overlapping functions likely also involve interactions between FLP and FAMA with the RETINOBLASTOMA-RELATED (RBR) protein. This article is protected by copyright. All rights reserved.The Plant Journal 02/2014; DOI:10.1111/tpj.12489 · 6.82 Impact Factor