EDITORIAL:

21st Century Plant Biology: Viva la Revolución?

Rich Jorgensen

Plant Cell 2007 19: 389-390. First Published on February 9, 2007; 10.1105/tpc.107.190280

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IN THIS ISSUE:

Two Tales of Chromatin Remodeling Converge on HUB1

Nancy A. Eckardt

Plant Cell 2007 19: 391-393.

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IN BRIEF:

Chromatin Remodeling ATPases and Plant Development

Nancy A. Eckardt

Plant Cell 2007 19: 394.

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Two Protein Kinases Required for ABA Signaling in Arabidopsis

Nancy A. Eckardt

Plant Cell 2007 19: 394.

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HISTORICAL PERSPECTIVE ESSAYS:

The Gene Balance Hypothesis: From Classical Genetics to Modern Genomics

James A. Birchler and Reiner A. Veitia

Plant Cell 2007 19: 395-402. First Published on February 9, 2007; 10.1105/tpc.106.049338

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RESEARCH ARTICLES:

Unique, Shared, and Redundant Roles for the Arabidopsis SWI/SNF Chromatin Remodeling ATPases BRAHMA and SPLAYED Staver Bezhani, Cara Winter, Steve Hershman, John D. Wagner, John F. Kennedy, Chang Seob Kwon, Jennifer Pfluger, Yanhui Su, and Doris Wagner Plant Cell 2007 19: 403-416. First Published on February 9, 2007; 10.1105/tpc.106.048272 Two SWI/SNF chromatin remodeling ATPases function as specific regulators of transcription, controlling expression of a small number of targets. Some genes uniquely depend on one, while others depend on both ATPases. Either remodeler is sufficient for proper embryogenesis. Interaction with complex components suggests formation of several tissue-specific SWI/SNF chromatin remodeling complexes. [Abstract] [Full Text] [PDF] [Supplemental Data] OPEN ACCESS ARTICLE

The Arabidopsis thaliana Homolog of Yeast BRE1 Has a Function in Cell Cycle Regulation during Early Leaf and Root Growth Delphine Fleury, Kristiina Himanen, Gerda Cnops, Hilde Nelissen, Tommaso Matteo Boccardi, Steven Maere, Gerrit T.S. Beemster, Pia Neyt, Sylvester Anami, Pedro Robles, José Luis Micol, Dirk Inzé, and Mieke Van Lijsebettens Plant Cell 2007 19: 417-432. First Published on February 28, 2007; 10.1105/tpc.106.041319 This study identified an Arabidopsis homolog of yeast and human Bre1 ubiquitin E3 ligase. Mutations in HISTONE MONOUBIQUITINATION1 (HUB1) affected leaf and root growth by impairing cell division. The authors postulate that HUB1 mediates gene activation and cell cycle regulation through histone modification. [Abstract] [Full Text] [PDF] [Supplemental Data] OPEN ACCESS ARTICLE

The Absence of Histone H2B Monoubiquitination in the Arabidopsis hub1 (rdo4) Mutant Reveals a Role for Chromatin Remodeling in Seed Dormancy Yongxiu Liu, Maarten Koornneef, and Wim J.J. Soppe Plant Cell 2007 19: 433-444. First Published on February 28, 2007; 10.1105/tpc.106.049221 Plants depend on the timing of life cycle transitions, such as seed germination and flowering initiation. This study found that mutants of HISTONE MONOUBIQUITINATION1 (HUB1) and HUB2 show reduced seed dormancy. HUB1 and HUB2 influence expression of dormancy-related genes and are needed for histone H2B monoubiquitination, suggesting a role for chromatin remodeling in the regulation of seed dormancy. [Abstract] [Full Text] [PDF] [Supplemental Data] OPEN ACCESS ARTICLE

Histone Deacetylases and ASYMMETRIC LEAVES2 Are Involved in the Establishment of Polarity in Leaves of Arabidopsis

Yoshihisa Ueno, Takaaki Ishikawa, Keiro Watanabe, Shinji Terakura, Hidekazu Iwakawa, Kiyotaka Okada, Chiyoko Machida, and Yasunori Machida

Plant Cell 2007 19: 445-457. First Published on February 9, 2007; 10.1105/tpc.106.042325

Two histone deacetylases, HDT1/HD2A and HDT2/HD2B, and both ASYMMETRIC LEAVES2 (AS2) and AS1 are involved in the control of miRNA expression and the determination of leaf polarity. These HDACs and both AS2 and AS1 were localized to the nucleolus and juxtaposed subnuclear bodies, respectively, and may interact in the generation of miRNAs.

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Arabidopsis BRANCHED1 Acts as an Integrator of Branching Signals within Axillary Buds

José Antonio Aguilar-Martínez, César Poza-Carrión, and Pilar Cubas

Plant Cell 2007 19: 458-472. First Published on February 16, 2007; 10.1105/tpc.106.048934

Shoot branching patterns, which determine plant form, light interception efficiency, and adaptation to resource availability, depend on a key developmental decision: whether axillary buds become branches or whether they remain dormant in leaf axils. This study characterized BRANCHED1, which represents a key point at which signals controlling branching are integrated within axillary buds.

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TCP Transcription Factors Control the Morphology of Shoot Lateral Organs via Negative Regulation of the Expression of Boundary-Specific Genes in Arabidopsis Tomotsugu Koyama, Masahiko Furutani, Masao Tasaka, and Masaru Ohme-Takagi Plant Cell 2007 19: 473-484. First Published on February 16, 2007; 10.1105/tpc.106.044792 In dicot embryogenesis, a shoot apical meristem is formed in the boundary region between two organ primordia. This study shows that the TCP family of transcription factors is involved in shoot meristem formation and the development of shoot lateral organs and that TCP3 specifically controls morphogenesis of shoot lateral organs by negative control of the expression of the boundary-specific CUC genes. [Abstract] [Full Text] [PDF] [Supplemental Data] OPEN ACCESS ARTICLE

Identification of Two Protein Kinases Required for Abscisic Acid Regulation of Seed Germination, Root Growth, and Gene Expression in Arabidopsis

Hiroaki Fujii, Paul E. Verslues, and Jian-Kang Zhu

Plant Cell 2007 19: 485-494. First Published on February 16, 2007; 10.1105/tpc.106.048538

The phytohormone abscisic acid (ABA) regulates various plant processes, including seed germination and seedling growth. Phosphorylation has been suggested to be important in ABA signaling, but little is known about the protein kinases needed. This study shows that two protein kinases, SnRK2.2 and SnRK2.3, act redundantly to control responses to ABA in seed germination, dormancy, and seedling growth.

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KANADI and Class III HD-Zip Gene Families Regulate Embryo Patterning and Modulate Auxin Flow during Embryogenesis in Arabidopsis Anat Izhaki and John L. Bowman Plant Cell 2007 19: 495-508. First Published on February 16, 2007; 10.1105/tpc.106.047472 Abnormal expression patterns of PIN1 in KANADI or Class III HD-Zip multiple mutants and phenotypes of plants with mutations in both families suggest that embryonic pattern formation along the central-peripheral axis results from interplay between auxin and the KANADI and Class III HD-Zip transcription factors whose defined spatial and temporal expression patterns may also be influenced by auxin. [Abstract] [Full Text] [PDF] [Supplemental Data] OPEN ACCESS ARTICLE

The Arabidopsis EIN3 Binding F-Box Proteins EBF1 and EBF2 Have Distinct but Overlapping Roles in Ethylene Signaling

Brad M. Binder, Joseph M. Walker, Jennifer M. Gagne, Thomas J. Emborg, Georg Hemmann, Anthony B. Bleecker, and Richard D. Vierstra

Plant Cell 2007 19: 509-523. First Published on February 16, 2007; 10.1105/tpc.106.048140

ETHYLENE-INSENSITIVE3 and EIN3-Like1 transcription factors, the main effectors of ethylene signaling, are posttranslationally regulated by EIN3 BINDING F-BOX1 and 2 through the ubiquitin/26S proteasome system. This proteolytic control fine-tunes ethylene responses by repressing signaling in the absence of ethylene, dampening signaling at high hormone levels, and promoting rapid recovery after ethylene dissipation.

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Centromere Function and Nondisjunction Are Independent Components of the Maize B Chromosome Accumulation Mechanism

Fangpu Han, Jonathan C. Lamb, Weichang Yu, Zhi Gao, and James A. Birchler

Plant Cell 2007 19: 524-533. First Published on February 23, 2007; 10.1105/tpc.106.049577

Selfish maize B chromosome accumulation by nondisjunction at the second pollen mitosis involves strong attachment of the two sister chromatids at a specific site within, or in close proximity to, the B centromere. The specificity of nondisjunction for the B centromere region and its unique mode of action indicate that it is controlled by a novel molecular mechanism that arose independently of normal centromere functions.

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Arabidopsis MYB26/MALE STERILE35 Regulates Secondary Thickening in the Endothecium and Is Essential for Anther Dehiscence Caiyun Yang, Zhengyao Xu, Jie Song, Katie Conner, Gema Vizcay Barrena, and Zoe A. Wilson Plant Cell 2007 19: 534-548. First Published on February 28, 2007; 10.1105/tpc.106.046391 The putative transcription factor MYB26 appears to function in determining endothecial cell development within the anther and in subsequent pollen release. It acts upstream of the lignin biosynthesis pathway, and this ability to regulate secondary thickening may have significant commercial applications for the wood and paper industry. [Abstract] [Full Text] [PDF] [Supplemental Data] OPEN ACCESS ARTICLE

Arabidopsis irregular xylem8 and irregular xylem9: Implications for the Complexity of Glucuronoxylan Biosynthesis

Maria J. Peña, Ruiqin Zhong, Gong-Ke Zhou, Elizabeth A. Richardson, Malcolm A. O'Neill, Alan G. Darvill, William S. York, and Zheng-Hua Ye

Plant Cell 2007 19: 549-563. First Published on February 23, 2007; 10.1105/tpc.106.049320

Glucuronoxylans (GXs) are major components of the secondary cell walls of diverse plant species. Nevertheless, the mechanisms of GX biosynthesis are poorly understood. This study shows that regulation of GX chain length and structure and the normal assembly and morphology of secondary cell walls require the coordinated action of three Arabidopsis glycosyl transferases.

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

Role of the MPN Subunits in COP9 Signalosome Assembly and Activity, and Their Regulatory Interaction with Arabidopsis Cullin3-Based E3 Ligases

Giuliana Gusmaroli, Pablo Figueroa, Giovanna Serino, and Xing Wang Deng

Plant Cell 2007 19: 564-581. First Published on February 16, 2007; 10.1105/tpc.106.047571

The evolutionarily conserved COP9 signalosome (CSN) complex functions in signaling and developmental processes, including embryogenesis, cell cycle, and plant responses to light and hormones. This study characterized two of the eight subunits of the complex, CSN5 and CSN6. CSN6A and CSN6B retain mostly redundant functions; CSN5A and CSN5B play unequal roles in the regulation of plant development.

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Tapetosomes in Brassica Tapetum Accumulate Endoplasmic Reticulum–Derived Flavonoids and Alkanes for Delivery to the Pollen Surface

Kai Hsieh and Anthony H.C. Huang

Plant Cell 2007 19: 582-596. First Published on February 16, 2007; 10.1105/tpc.106.049049

Tapetosomes function as subcellular metabolic sinks, accumulating ER-derived flavonoids in vesicles as well as alkanes and oleosins in lipid droplets. These tapetosome components are discharged to the pollen surface upon cell death as the predominant coat ingredients that protect the haploidic pollen from UV damage and water loss as well as aid water uptake.

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Arabidopsis Vacuolar Sorting Mutants (green fluorescent seed) Can Be Identified Efficiently by Secretion of Vacuole-Targeted Green Fluorescent Protein in Their Seeds Kentaro Fuji, Tomoo Shimada, Hideyuki Takahashi, Kentaro Tamura, Yasuko Koumoto, Shigeru Utsumi, Keito Nishizawa, Nobuyuki Maruyama, and Ikuko Hara-Nishimura Plant Cell 2007 19: 597-609. First Published on February 9, 2007; 10.1105/tpc.106.045997 Vacuolar protein sorting mutants were isolated by mutagenizing transformant seeds expressing GFP-CT24. Mutant seeds fluoresced strongly, while the wild type did not, suggesting that a defect in vacuolar sorting provided fluorescent seeds due to secretion of GFP-CT24 out of the cells. Ten vacuolar sorting mutants were identified and mapped to VSR1, KAM2/GRV2, and other loci. [Abstract] [Full Text] [PDF] [Supplemental Data] OPEN ACCESS ARTICLE

NUCLEOPORIN85 Is Required for Calcium Spiking, Fungal and Bacterial Symbioses, and Seed Production in Lotus japonicus

Katsuharu Saito, Makoto Yoshikawa, Koji Yano, Hiroki Miwa, Hisaki Uchida, Erika Asamizu, Shusei Sato, Satoshi Tabata, Haruko Imaizumi-Anraku, Yosuke Umehara, Hiroshi Kouchi, Yoshikatsu Murooka, Krzysztof Szczyglowski, J. Allan Downie, Martin Parniske, Makoto Hayashi, and Masayoshi Kawaguchi

Plant Cell 2007 19: 610-624. First Published on February 16, 2007; 10.1105/tpc.106.046938

The Lotus japonicus nucleoporin NUP85 functions in the common Sym pathway for both fungal and rhizobial symbioses. It may be part of a specific nuclear pore subcomplex crucial for both nodule and arbuscule formation as well as for seed production.

[Abstract] [Full Text] [PDF]

Dominant-Negative Modification Reveals the Regulatory Function of the Multimeric Cysteine Synthase Protein Complex in Transgenic Tobacco

Markus Wirtz and Rüdiger Hell

Plant Cell 2007 19: 625-639. First Published on February 9, 2007; 10.1105/tpc.106.043125

Formation of the cysteine synthase complex (CSC) and interaction of its subunits play crucial roles in plant cysteine biosynthesis and entry of reduced sulfur into metabolism. CSC is a metabolic enzyme complex with regulatory function rather than a gate for substrate channelling. Compartmentalization of CSC may allow overcompensation by organellar CSC sites when cytosolic CSC equilibrium is disrupted.

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

Lack of Respiratory Chain Complex I Impairs Alternative Oxidase Engagement and Modulates Redox Signaling during Elicitor-Induced Cell Death in Tobacco

Guillaume Vidal, Miquel Ribas-Carbo, Marie Garmier, Guy Dubertret, Allan G. Rasmusson, Chantal Mathieu, Christine H. Foyer, and Rosine De Paepe

Plant Cell 2007 19: 640-655. First Published on February 2, 2007; 10.1105/tpc.106.044461

Alternative oxidase (AOX) activity is induced during the hypersensitive response in tobacco, but AOX engagement is impaired in a CMSII complex I mutant in stress and nonstress conditions. This suggests some flexibility in respiratory routes and antioxidants in response to elicitors, and sustained ATP production rather than AOX activity alone or mitochondrial ROS might be important in cell death.

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Light-Induced Energy Dissipation in Iron-Starved Cyanobacteria: Roles of OCP and IsiA Proteins

Adjélé Wilson, Clémence Boulay, Annegret Wilde, Cheryl A. Kerfeld, and Diana Kirilovsky

Plant Cell 2007 19: 656-672. First Published on February 16, 2007; 10.1105/tpc.106.045351

Cyanobacteria limit harmful excess light by various quenching mechanisms. Iron stress–induced IsiA was thought to play a protective role in blue light–induced nonphotochemical quenching in iron-depleted cells, but this study shows that in iron-stressed and nonstressed cells alike, blue light–induced fluorescence quenching is associated with the Orange Carotenoid Protein and not with IsiA

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Thioredoxin h5 Is Required for Victorin Sensitivity Mediated by a CC-NBS-LRR Gene in Arabidopsis

Teresa A. Sweat and Thomas J. Wolpert

Plant Cell 2007 19: 673-687. First Published on February 23, 2007; 10.1105/tpc.106.047563

Victorin is a host-selective toxin from C. victoriae that induces programmed cell death. ATTRX5 is specifically required for the victorin response in Arabidopsis and is highly induced in sensitive Arabidopsis following victorin treatment. Only one of the two ATTRX5 active-site Cys residues is required for the victorin response, suggesting that ATTRX5 function involves an atypical mechanism of action.

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A Conserved Carboxylesterase Is a SUPPRESSOR OF AVRBST-ELICITED RESISTANCE in Arabidopsis Sébastien Cunnac, Ariane Wilson, Jamie Nuwer, Angela Kirik, Gayathri Baranage, and Mary Beth Mudgett Plant Cell 2007 19: 688-705. First Published on February 9, 2007; 10.1105/tpc.106.048710 AvrBsT, a type III effector from Xanthomonas campestris pathovar vesicatoria, which is translocated into plant cells during infection, is predicted to encode a cysteine protease that targets intracellular host proteins. The carboxylesterase SUPPRESSOR OF AVRBST-ELICITED RESISTANCE1 inhibits AvrBsT-dependent phenotypes in Arabidopsis. [Abstract] [Full Text] [PDF] [Supplemental Data] OPEN ACCESS ARTICLE

Roles for Rice Membrane Dynamics and Plasmodesmata during Biotrophic Invasion by the Blast Fungus Prasanna Kankanala, Kirk Czymmek, and Barbara Valent Plant Cell 2007 19: 706-724. First Published on February 23, 2007; 10.1105/tpc.106.046300 The fungus Magnaporthe oryzae invades living plant cells by means of intracellular invasive hyphae (IH) that grow from one cell to the next. Live-cell imaging showing spatial and temporal development of IH proves that they are wrapped in plant membrane as they sequentially invade living rice cells and suggests that they manipulate plasmodesmata for their own cell-to-cell movement. [Abstract] [Full Text] [PDF] [Supplemental Data] OPEN ACCESS ARTICLE

CORRECTIONS:

Correction

Plant Cell 2007 19: 725. First Published on February 16, 2007; 10.1105/tpc.107.190260

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Correction

Plant Cell 2007 19: 726. First Published on February 16, 2007; 10.1105/tpc.107.190261

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