IN THIS ISSUE:

High-Resolution Imaging of Cortical Microtubule Arrays

Nancy A. Eckardt

Plant Cell 2008 20: 817-819. First Published on April 25, 2008; 10.1105/tpc.108.060228

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IN BRIEF:

Surprising New Member of the KNOTTED1-Like Family of Transcriptional Regulators Lacks a Homeodomain

Jennifer Mach

Plant Cell 2008 20: 820. First Published on April 8, 2008; 10.1105/tpc.108.200410

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PLP3 Proteins Function in Microtubule Assembly in Arabidopsis

Nancy A. Eckardt

Plant Cell 2008 20: 821. First Published on April 4, 2008; 10.1105/tpc.108.200411

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Probing the Role of Auxin in Wood Formation

Kathleen L. Farquharson

Plant Cell 2008 20: 822. First Published on April 18, 2008; 10.1105/tpc.108.200412

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Regulation of Plastid Gene Expression in the Chloroplast-to-Chromoplast Transition

Nancy R. Hofmann

Plant Cell 2008 20: 823. First Published on April 25, 2008; 10.1105/tpc.108.200413

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LETTERS TO THE EDITOR:

The coi1-16 Mutant Harbors a Second Site Mutation Rendering PEN2 Nonfunctional

Lore Westphal, Dierk Scheel, and Sabine Rosahl

Plant Cell 2008 20: 824-826. First Published on April 22, 2008; 10.1105/tpc.107.056895

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RESEARCH ARTICLES:

Histone Acetylation and Chromatin Remodeling Are Required for UV-B–Dependent Transcriptional Activation of Regulated Genes in Maize

Paula Casati, Mabel Campi, Feixia Chu, Nagi Suzuki, David Maltby, Shenheng Guan, Alma L. Burlingame, and Virginia Walbot

Plant Cell 2008 20: 827-842. First Published on April 8, 2008; 10.1105/tpc.107.056457

This work examines the nuclear protein changes associated with UV-B exposure in maize lines that differ in UV sensitivity. Proteomic, ChIP, and nuclease sensitivity assays show that the UV-tolerant lines produce more protein changes and more open chromatin structure around UV-response genes after UV exposure, demonstrating that chromatin remodeling is key to maize acclimation to UV-B.

[Abstract] [Full Text] [PDF] [Supplemental Data]

Dissecting the Molecular Basis of the Regulation of Wood Formation by Auxin in Hybrid Aspen

Jeanette Nilsson, Anna Karlberg, Henrik Antti, Manuel Lopez-Vernaza, Ewa Mellerowicz, Catherine Perrot-Rechenmann, Göran Sandberg, and Rishikesh P. Bhalerao

Plant Cell 2008 20: 843-855. First Published on April 18, 2008; 10.1105/tpc.107.055798

The plant hormone auxin regulates wood formation. This work identifies auxin-responsive genes potentially involved in secondary xylem development in hybrid aspen and shows that perturbing auxin signaling affects cell divisions in the cambium and reduces the size of fibers and vessels. A mechanism for auxin-based regulation of secondary xylem development is proposed.

[Abstract] [Full Text] [PDF] [Supplemental Data]

Plastid Transcriptomics and Translatomics of Tomato Fruit Development and Chloroplast-to-Chromoplast Differentiation: Chromoplast Gene Expression Largely Serves the Production of a Single Protein Sabine Kahlau and Ralph Bock Plant Cell 2008 20: 856-874. First Published on April 25, 2008; 10.1105/tpc.107.055202 An oligonucleotide microarray is used in this work to examine the contributions of transcriptional, posttranscriptional, and translational processes to the developmental regulation of plastid gene expression. While most genes are downregulated during fruit ripening, gene expression machinery is maintained for the production of the only plastid-encoded protein involved in fatty acid biosynthesis. [Abstract] [Full Text] [PDF] [Supplemental Data] OPEN ACCESS ARTICLE

KNOX Lost the OX: The Arabidopsis KNATM Gene Defines a Novel Class of KNOX Transcriptional Regulators Missing the Homeodomain

Enrico Magnani and Sarah Hake

Plant Cell 2008 20: 875-887. First Published on April 8, 2008; 10.1105/tpc.108.058495

This work identifies KNATM, a novel member of the KNOTTED1-like homeobox protein class. KNATM contains the conserved MEINOX domain but no homeodomain. KNATM overexpression gives defects in leaf proximal-distal patterning. The KNATM MEINOX domain is sufficient for interaction with other homeobox proteins, revealing a homeodomain-independent mechanism of transcriptional regulation.

[Abstract] [Full Text] [PDF] [Supplemental Data]

Interaction of KNAT6 and KNAT2 with BREVIPEDICELLUS and PENNYWISE in Arabidopsis Inflorescences

Laura Ragni, Enric Belles-Boix, Markus Günl, and Véronique Pautot

Plant Cell 2008 20: 888-900. First Published on April 4, 2008; 10.1105/tpc.108.058230

This work explores the genetic interactions between four homeobox genes during inflorescence growth. BREVIPEDICELLUS and PENNYWISE were found to restrict KNAT6 and KNAT2 expression to promote correct internode patterning and phyllotaxy.

[Abstract] [Full Text] [PDF] [Supplemental Data]

REBELOTE, SQUINT, and ULTRAPETALA1 Function Redundantly in the Temporal Regulation of Floral Meristem Termination in Arabidopsis thaliana

Nathanaël Prunet, Patrice Morel, Anne-Marie Thierry, Yuval Eshed, John L. Bowman, Ioan Negrutiu, and Christophe Trehin

Plant Cell 2008 20: 901-919. First Published on April 25, 2008; 10.1105/tpc.107.053306

To make a determinate flower, the floral meristem (FM) must terminate after a set number of whorls. This study reveals new players and gene interactions involved in FM termination and suggests that this process corresponds to a temporal sequence of events and requires AGAMOUS activity in a 4th whorl subdomain.

[Abstract] [Full Text] [PDF] [Supplemental Data]

HD-ZIP III Activity Is Modulated by Competitive Inhibitors via a Feedback Loop in Arabidopsis Shoot Apical Meristem Development

Youn-Sung Kim, Sang-Gyu Kim, Minsun Lee, Ilha Lee, Hye-Young Park, Pil Joon Seo, Jae-Hoon Jung, Eun-Jung Kwon, Se Won Suh, Kyung-Hee Paek, and Chung-Mo Park

Plant Cell 2008 20: 920-933. First Published on April 11, 2008; 10.1105/tpc.107.057448

Class III homeodomain-leucine zipper (HD-ZIP III) transcription factors play a key role in shoot apical meristem development. This work shows that the HD-ZIP III activities are regulated by competitive inhibitors, which form nonfunctional heterodimers with the HD-ZIP III proteins through the ZIP motifs.

[Abstract] [Full Text] [PDF] [Supplemental Data]

The Receptor Kinase CORYNE of Arabidopsis Transmits the Stem Cell–Limiting Signal CLAVATA3 Independently of CLAVATA1

Ralf Müller, Andrea Bleckmann, and Rüdiger Simon

Plant Cell 2008 20: 934-946. First Published on April 1, 2008; 10.1105/tpc.107.057547

Stem cell fate in meristems is regulated by the CLAVATA signaling pathway. It is shown here that CORYNE kinase is required for CLAVATA signalling and forms a signaling module with the receptor protein CLAVATA2. These proteins may act together to control aspects of plant development, including pedicel and anther development.

[Abstract] [Full Text] [PDF] [Supplemental Data]

Distinct Light-Initiated Gene Expression and Cell Cycle Programs in the Shoot Apex and Cotyledons of Arabidopsis

Enrique López-Juez, Edyta Dillon, Zoltán Magyar, Safina Khan, Saul Hazeldine, Sarah M. de Jager, James A.H. Murray, Gerrit T.S. Beemster, László Bögre, and Hugh Shanahan

Plant Cell 2008 20: 947-968. First Published on April 18, 2008; 10.1105/tpc.107.057075

Whole-genome expression analysis identifies processes underlying light-mediated shoot apex and leaf growth activation. They include rapid light repression of genes associated with proteolysis, signaling, and specific transcription factors as well as hormonal responses, synchronous cell growth, and cell proliferation.

[Abstract] [Full Text] [PDF] [Supplemental Data]

Phosducin-Like Protein 3 Is Required for Microtubule-Dependent Steps of Cell Division but Not for Meristem Growth in Arabidopsis M. Mar Castellano and Robert Sablowski Plant Cell 2008 20: 969-981. First Published on April 4, 2008; 10.1105/tpc.107.057737 Repeated cell divisions in the meristem give rise to new organs and tissues in plants. This work describes an essential player in microtubule biology in Arabidopsis and shows that shoot meristem cells are remarkably tolerant to microtubule-related mitotic defects. [Abstract] [Full Text] [PDF] [Supplemental Data] OPEN ACCESS ARTICLE

Analysis of Cortical Arrays from Tradescantia virginiana at High Resolution Reveals Discrete Microtubule Subpopulations and Demonstrates That Confocal Images of Arrays Can Be Misleading

Deborah A. Barton, Marylin Vantard, and Robyn L. Overall

Plant Cell 2008 20: 982-994. First Published on April 22, 2008; 10.1105/tpc.108.058503

Plant cortical microtubule arrays were imaged using high-resolution scanning electron microscopy to show that they are composed of two spatially discrete subpopulations with different stabilities. EB1 and katanin were immunolocalized to microtubules within the arrays. Correlative microscopy showed that confocal images of fluorescently tagged arrays can be misleading.

[Abstract] [Full Text] [PDF] [Supplemental Data]

Arabidopsis SCARs Function Interchangeably to Meet Actin-Related Protein 2/3 Activation Thresholds during Morphogenesis

Chunhua Zhang, Eileen L. Mallery, Jessica Schlueter, Shanjin Huang, Youran Fan, Steven Brankle, Christopher J. Staiger, and Daniel B. Szymanski

Plant Cell 2008 20: 995-1011. First Published on April 18, 2008; 10.1105/tpc.107.055350

This quantitative approach to morphogenesis and actin cytoskeleton biochemistry shows that plant SCAR proteins function as interchangeable positive regulators of the WAVE-ARP2/3 growth control pathway. The relative importance of individual SCARs depends both on the biochemical efficiency of ARP2/3 activation and on cell type–specific differences in gene expression levels.

[Abstract] [Full Text] [PDF] [Supplemental Data]

Minor Antenna Proteins CP24 and CP26 Affect the Interactions between Photosystem II Subunits and the Electron Transport Rate in Grana Membranes of Arabidopsis

Silvia de Bianchi, Luca Dall'Osto, Giuseppe Tognon, Tomas Morosinotto, and Roberto Bassi

Plant Cell 2008 20: 1012-1028. First Published on April 1, 2008; 10.1105/tpc.107.055749

Pigment binding proteins in the antenna complex enhance a plant's ability to absorb light energy during photosynthesis. This study investigates the contribution of two such proteins, Chlorophyll Protein 24 (CP24) and CP26, to photosynthesis in Arabidopsis. While photosynthesis is impaired in CP24 knockout plants, it is not affected by removal of CP26 or, surprisingly, of both CP24 and CP26.

[Abstract] [Full Text] [PDF] [Supplemental Data]

Thylakoid Membrane Remodeling during State Transitions in Arabidopsis

Silvia G. Chuartzman, Reinat Nevo, Eyal Shimoni, Dana Charuvi, Vladimir Kiss, Itzhak Ohad, Vlad Brumfeld, and Ziv Reich

Plant Cell 2008 20: 1029-1039. First Published on April 8, 2008; 10.1105/tpc.107.055830

Adaptation of photosynthetic organisms to fluctuations in light conditions is achieved by rapid state transition processes. Using several microscopic techniques, this study shows that state transitions in Arabidopsis are accompanied by large-scale structural rearrangments of the thylakoid membranes. It also presents a model for these membrane alterations.

[Abstract] [Full Text] [PDF] [Supplemental Data]

β-AMYLASE4, a Noncatalytic Protein Required for Starch Breakdown, Acts Upstream of Three Active β-Amylases in Arabidopsis Chloroplasts Daniel C. Fulton, Michaela Stettler, Tabea Mettler, Cara K. Vaughan, Jing Li, Perigio Francisco, Manuel Gil, Heike Reinhold, Simona Eicke, Gaëlle Messerli, Gary Dorken, Karen Halliday, Alison M. Smith, Steven M. Smith, and Samuel C. Zeeman Plant Cell 2008 20: 1040-1058. First Published on April 4, 2008; 10.1105/tpc.107.056507 This study shows that at least four of the nine β-amylase (BAM)–like proteins in Arabidopsis are chloroplastic. Two, BAM1 and BAM3, are active amylases and mediate maltose production from starch breakdown. BAM4, which lacks measurable catalytic activity, also influences starch breakdown and is proposed to have a facilitatory or regulatory function. [Abstract] [Full Text] [PDF] [Supplemental Data] OPEN ACCESS ARTICLE

The Structure of Sucrose Phosphate Synthase from Halothermothrix orenii Reveals Its Mechanism of Action and Binding Mode Teck Khiang Chua, Janusz M. Bujnicki, Tien-Chye Tan, Frederick Huynh, Bharat K. Patel, and J. Sivaraman Plant Cell 2008 20: 1059-1072. First Published on April 18, 2008; 10.1105/tpc.107.051193 Sucrose phosphate synthase (SPS) plays a key role in the production of sucrose in plants, cyanobacteria, and proteobacteria. This study reports the crystal structure of SPS from the thermohalophilic bacterium Halothermothrix orenii and presents complexes with its substrate and product. This molecule may represent a valid model for the catalytic domain and reaction mechanism of plant SPSs. [Abstract] [Full Text] [PDF] [Supplemental Data] OPEN ACCESS ARTICLE

Functional and Physiological Characterization of Arabidopsis INOSITOL TRANSPORTER1, a Novel Tonoplast-Localized Transporter for myo-Inositol

Sabine Schneider, Diana Beyhl, Rainer Hedrich, and Norbert Sauer

Plant Cell 2008 20: 1073-1087. First Published on April 25, 2008; 10.1105/tpc.107.055632

This work describes a novel Arabidopsis inositol transporter that localizes to the tonoplast membrane and moves inositol out of the vacuole. Mutants lacking this transporter show reduced root growth, which can be complemented by exogenous inositol, and increased myo-inositol levels in their cells.

[Abstract] [Full Text] [PDF] [Supplemental Data]

Reduced V-ATPase Activity in the trans-Golgi Network Causes Oxylipin-Dependent Hypocotyl Growth Inhibition in Arabidopsis

Angela Brüx, Tzu-Yin Liu, Melanie Krebs, York-Dieter Stierhof, Jan U. Lohmann, Otto Miersch, Claus Wasternack, and Karin Schumacher

Plant Cell 2008 20: 1088-1100. First Published on April 25, 2008; 10.1105/tpc.108.058362

Activity of the vacuolar H⁺-ATPase, a eukaryotic endomembrane proton pump, is required for plant cell expansion. Here, we show that the compromised cell expansion in mutants with reduced V-ATPase activity is not due to limited turgor pressure but caused by a cell wall defect that in turn causes hormone-mediated growth inhibition.

[Abstract] [Full Text] [PDF] [Supplemental Data]

Analysis of the Arabidopsis Histidine Kinase ATHK1 Reveals a Connection between Vegetative Osmotic Stress Sensing and Seed Maturation Dana J. Wohlbach, Betania F. Quirino, and Michael R. Sussman Plant Cell 2008 20: 1101-1117. First Published on April 25, 2008; 10.1105/tpc.107.055871 Studies using null and overexpressing mutants of the Arabidopsis water stress sensory protein ATHK1 reveal that this single protein helps to regulate abscisic acid levels both in vegetative plant tissues after osmotic stress and in maturing seeds. [Abstract] [Full Text] [PDF] [Supplemental Data] OPEN ACCESS ARTICLE

Conserved C-Terminal Motifs Required for Avirulence and Suppression of Cell Death by Phytophthora sojae effector Avr1b

Daolong Dou, Shiv D. Kale, Xinle Wang, Yubo Chen, Qunqing Wang, Xia Wang, Rays H.Y. Jiang, Felipe D. Arredondo, Ryan G. Anderson, Poulami B. Thakur, John M. McDowell, Yuanchao Wang, and Brett M. Tyler

Plant Cell 2008 20: 1118-1133. First Published on April 4, 2008; 10.1105/tpc.107.057067

In this study, the authors examine the function of effector protein Avr1b from the oomycete pathogen Phytophthora sojae. First, they show that Avr1b overexpression increases virulence. Second, Avr1b can suppress programmed cell death in plants and yeast. Third, this suppression is dependent on two conserved motifs present in many predicted oomycete effectors.

[Abstract] [Full Text] [PDF] [Supplemental Data]

Activated Expression of an Arabidopsis HD-START Protein Confers Drought Tolerance with Improved Root System and Reduced Stomatal Density Hong Yu, Xi Chen, Yuan-Yuan Hong, Yao Wang, Ping Xu, Sheng-Dong Ke, Hai-Yan Liu, Jian-Kang Zhu, David J. Oliver, and Cheng-Bin Xiang Plant Cell 2008 20: 1134-1151. First Published on April 30, 2008; 10.1105/tpc.108.058263 This study reports a gain-of-function mutation in Arabidopsis that results in drought-resistant plants with fewer stomata, longer and more extensively branched roots, and increased levels of the stress mediators abscisic acid, superoxide dismutase, and proline. Overexpressing this gene in tobacco imparts tolerance to drought. [Abstract] [Full Text] [PDF] [Supplemental Data] OPEN ACCESS ARTICLE

Identification and Regulation of TPS04/GES, an Arabidopsis Geranyllinalool Synthase Catalyzing the First Step in the Formation of the Insect-Induced Volatile C₁₆-Homoterpene TMTT

Marco Herde, Katrin Gärtner, Tobias G. Köllner, Benjamin Fode, Wilhelm Boland, Jonathan Gershenzon, Christiane Gatz, and Dorothea Tholl

Plant Cell 2008 20: 1152-1168. First Published on April 8, 2008; 10.1105/tpc.106.049478

This work identifies an Arabidopsis terpene synthase that is required for the synthesis of (E,E)-geranyllinalool, a precursor of the volatile secondary metabolite TMTT. It thus lays the groundwork for assessing the role of TMTT in indirect defense responses and elucidating the signaling network that regulates TMTT synthesis.

[Abstract] [Full Text] [PDF] [Supplemental Data]

Fungal Effector Protein AVR2 Targets Diversifying Defense-Related Cys Proteases of Tomato

Mohammed Shabab, Takayuki Shindo, Christian Gu, Farnusch Kaschani, Twinkal Pansuriya, Raju Chintha, Anne Harzen, Tom Colby, Sophien Kamoun, and Renier A.L. van der Hoorn

Plant Cell 2008 20: 1169-1183. First Published on April 30, 2008; 10.1105/tpc.107.056325

A set of seven active papain-like proteases is present in the apoplast of tomato during defense. Two of these (PIP1 and RCR3) are specifically induced by treatment with benzothiadiazole, which triggers the salicylic acid–regulated defense pathway. These two proteases are under diversifying selection and are specifically targeted for inhibition by the fungal AVR2 effector protein.

[Abstract] [Full Text] [PDF] [Supplemental Data]

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