COMMENTARY:

Returning to Our Roots: Making Plant Biology Research Relevant to Future Challenges in Agriculture

Steven J. Rothstein

Plant Cell 2007 19: 2695-2699. First Published on September 14, 2007; doi:10.1105/tpc.107.053074

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IN THIS ISSUE:

Positive and Negative Feedback Coordinate Regulation of Disease Resistance Gene Expression

Nancy A. Eckardt

Plant Cell 2007 19: 2700-2702. doi:10.1105/tpc.107.056226

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IN BRIEF:

Shoot Meristem Development Depends on N-Myristoylation of SnRK1

Nancy A. Eckardt

Plant Cell 2007 19: 2703. doi:10.1105/tpc.107.190910

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Brassinosteroid Signaling Involves the Nucleocytoplasmic Shuttling Activity of BZR1

Nancy A. Eckardt

Plant Cell 2007 19: 2703. doi:10.1105/tpc.107.190911

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RESEARCH ARTICLES:

Oryza sativa Dicer-like4 Reveals a Key Role for Small Interfering RNA Silencing in Plant Development Bin Liu, Zhiyu Chen, Xianwei Song, Chunyan Liu, Xia Cui, Xianfeng Zhao, Jun Fang, Wenying Xu, Huiyong Zhang, Xiujie Wang, Chengcai Chu, Xingwang Deng, Yongbiao Xue, and Xiaofeng Cao Plant Cell 2007 19: 2705-2718. First Published on September 28, 2007; doi:10.1105/tpc.107.052209 Specialized functions of Arabidopsis DICER-LIKE genes (DCLs) are well characterized, but those in rice remain elusive. This work shows that DCL4 is the major DCL locus responsible for the processing of 21-nucleotide siRNAs in rice and suggests that processing of small interfering RNAs by Os DCL4 endonuclease has a broader role in rice development than the At DCL4 protein has in Arabidopsis. [Abstract] [Full Text] [PDF] [Supplemental Data] OPEN ACCESS ARTICLE

The Arabidopsis BEL1-LIKE HOMEODOMAIN Proteins SAW1 and SAW2 Act Redundantly to Regulate KNOX Expression Spatially in Leaf Margins

Ravi Kumar, Kumuda Kushalappa, Dietmute Godt, Mark S. Pidkowich, Sandro Pastorelli, Shelley R. Hepworth, and George W. Haughn

Plant Cell 2007 19: 2719-2735. First Published on September 14, 2007; doi:10.1105/tpc.106.048769

The genes SAWTOOTH1 and SAWTOOTH2 encode redundant regulatory proteins that are required to establish normal leaf shape. These genes likely act by promoting normal patterns of growth in the developing leaf, in part by suppressing the expression of other growth regulators that are normally found in the shoot apical meristem.

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The GIGANTEA-Regulated MicroRNA172 Mediates Photoperiodic Flowering Independent of CONSTANS in Arabidopsis Jae-Hoon Jung, Yeon-Hee Seo, Pil Joon Seo, Jose Luis Reyes, Ju Yun, Nam-Hai Chua, and Chung-Mo Park Plant Cell 2007 19: 2736-2748. First Published on September 21, 2007; doi:10.1105/tpc.107.054528 CONSTANS plays a central role in photoperiodic flowering. This work defines an additional flowering genetic pathway that regulates flowering initiation in response to daylength changes, in which microRNA172 promotes photoperiodic flowering independent of CONSTANS. [Abstract] [Full Text] [PDF] [Supplemental Data] OPEN ACCESS ARTICLE

Nucleocytoplasmic Shuttling of BZR1 Mediated by Phosphorylation Is Essential in Arabidopsis Brassinosteroid Signaling Hojin Ryu, Kangmin Kim, Hyunwoo Cho, Joonghyuk Park, Sunghwa Choe, and Ildoo Hwang Plant Cell 2007 19: 2749-2762. First Published on September 14, 2007; doi:10.1105/tpc.107.053728 Brassinosteroid is an essential phytohormone that regulates plant growth and development. The phosphorylation status of the transcription factor BZR1 tunes the intensity of BR signaling in various tissues and developmental stages of plants by modulating nucleocytoplasmic shuttling of BZR1 through interaction with 14-3-3 proteins. [Abstract] [Full Text] [PDF] [Supplemental Data] OPEN ACCESS ARTICLE

The Arabidopsis CLASP Gene Encodes a Microtubule-Associated Protein Involved in Cell Expansion and Division

J. Christian Ambrose, Tsubasa Shoji, Amanda M. Kotzer, Jamie A. Pighin, and Geoffrey O. Wasteneys

Plant Cell 2007 19: 2763-2775. First Published on September 14, 2007; doi:10.1105/tpc.107.053777

This work demonstrates that the CLASP ortholog in plant cells is a microtubule-associated protein that localizes along the full length of microtubules and shows enrichment at growing plus ends. clasp-1 mutants have defects in interphase and mitotic microtubule arrays and exhibit increased drug sensitivity. The data indicate a role for CLASP in stabilizing microtubules.

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The MYB46 Transcription Factor Is a Direct Target of SND1 and Regulates Secondary Wall Biosynthesis in Arabidopsis

Ruiqin Zhong, Elizabeth A. Richardson, and Zheng-Hua Ye

Plant Cell 2007 19: 2776-2792. First Published on September 21, 2007; doi:10.1105/tpc.107.053678

Biosynthesis of secondary walls requires the coordinated expression of secondary wall biosynthetic genes. This article presents the discovery of a MYB transcription factor, MYB46, as a direct target of SND1 and demonstrates that MYB46 is another key regulator in activating the biosynthetic pathways for cellulose, xylan, and lignin.

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LITTLE NUCLEI Genes Affecting Nuclear Morphology in Arabidopsis thaliana

Travis A. Dittmer, Nicola J. Stacey, Keiko Sugimoto-Shirasu, and Eric J. Richards

Plant Cell 2007 19: 2793-2803. First Published on September 14, 2007; doi:10.1105/tpc.107.053231

This work shows that disruption of LINC genes causes a reduction in nuclear size and altered nuclear morphology, indicating that the LINC coiled-coil proteins are important determinants of plant nuclear structure.

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N-Myristoylation Regulates the SnRK1 Pathway in Arabidopsis

Michèle Pierre, José A. Traverso, Bertrand Boisson, Séverine Domenichini, David Bouchez, Carmela Giglione, and Thierry Meinnel

Plant Cell 2007 19: 2804-2821. First Published on September 7, 2007; doi:10.1105/tpc.107.051870

N-myristoylation is a lipid modification ensuring the proper function and intracellular trafficking of proteins involved in signaling pathways. Comprehensive investigation of protein N-myristoylation in Arabidopsis shows that this function is critical for shoot apical meristem development and that the heterotrimeric SNF1-related kinase SnRK1 is a crucial primary target.

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INCURVATA2 Encodes the Catalytic Subunit of DNA Polymerase and Interacts with Genes Involved in Chromatin-Mediated Cellular Memory in Arabidopsis thaliana

José María Barrero, Rebeca González-Bayón, Juan Carlos del Pozo, María Rosa Ponce, and José Luis Micol

Plant Cell 2007 19: 2822-2838. First Published on September 14, 2007; doi:10.1105/tpc.107.054130

Genetic analyses show that INCURVATA2 interacts with chromatin-remodeling genes TERMINAL FLOWER2 and CURLY LEAF, suggesting genetic and molecular interactions between chromatin remodeling factors and components of the DNA replication machinery.

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The Exposed N-Terminal Tail of the D1 Subunit Is Required for Rapid D1 Degradation during Photosystem II Repair in Synechocystis sp PCC 6803

Josef Komenda, Martin Tichy, Ondrej Prásil, Jana Knoppová, Stanislava Kuviková, Remco de Vries, and Peter J. Nixon

Plant Cell 2007 19: 2839-2854. First Published on September 28, 2007; doi:10.1105/tpc.107.053868

One of the most important photoprotective mechanisms in plants and cyanobacteria is the selective replacement of photodamaged D1 during the repair of the photosystem II (PSII) complex. This work investigates the mechanism by which the damaged D1 subunit is removed from PSII complexes in cyanobacteria and shows that the exposed N-terminal region is required for degradation.

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

An Oncoprotein from the Plant Pathogen Agrobacterium Has Histone Chaperone–Like Activity

Shinji Terakura, Yoshihisa Ueno, Hideaki Tagami, Saeko Kitakura, Chiyoko Machida, Hiroetsu Wabiko, Hiroji Aiba, Léon Otten, Hironaka Tsukagoshi, Kenzo Nakamura, and Yasunori Machida

Plant Cell 2007 19: 2855-2865. First Published on September 21, 2007; doi:10.1105/tpc.106.049551

Agrobacterium tumefaciens protein 6b stimulates aberrant proliferation of plant cells. This work shows that 6b specifically binds histone H3, forms nucleosomes on DNA in the presence of core histones in vitro, and affects transcription patterns of a variety of genes in plants, suggesting a relationship between alterations in nucleosome structure and the expression of growth-regulating genes.

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

AP2-ERF Transcription Factors Mediate Nod Factor–Dependent Mt ENOD11 Activation in Root Hairs via a Novel cis-Regulatory Motif

Andry Andriankaja, Aurélien Boisson-Dernier, Lisa Frances, Laurent Sauviac, Alain Jauneau, David G. Barker, and Fernanda de Carvalho-Niebel

Plant Cell 2007 19: 2866-2885. First Published on September 7, 2007; doi:10.1105/tpc.107.052944

Rhizobium Nod factors (NFs) are key signaling molecules essential for the establishment of the nitrogen-fixing symbiosis in legumes. This work describes the characterization of novel cis-regulatory sequences required for NF-dependent root hair–specific gene expression in Medicago truncatula as well as both activator and repressor-type trans-interacting ERF factors.

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

Molecular Architecture of Strictosidine Glucosidase: The Gateway to the Biosynthesis of the Monoterpenoid Indole Alkaloid Family

Leif Barleben, Santosh Panjikar, Martin Ruppert, Juergen Koepke, and Joachim Stöckigt

Plant Cell 2007 19: 2886-2897. First Published on September 21, 2007; doi:10.1105/tpc.106.045682

Strictosidine ß-D-glucosidase (SG) functions in the biosynthesis of monoterpenoid indole alkaloids in plants. This work reports structural analysis and site-directed mutagenesis experiments describing native SG and the complex of an inactive mutant with the substrate strictosidine. The results reveal a unique conformation of the catalytic pocket specific to the SG enzyme.

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

Crystal Structures of Flax Rust Avirulence Proteins AvrL567-A and -D Reveal Details of the Structural Basis for Flax Disease Resistance Specificity

Ching-I A. Wang, Gregor Guncar, Jade K. Forwood, Trazel Teh, Ann-Maree Catanzariti, Gregory J. Lawrence, Fionna E. Loughlin, Joel P. Mackay, Horst Joachim Schirra, Peter A. Anderson, Jeffrey G. Ellis, Peter N. Dodds, and Bostjan Kobe

Plant Cell 2007 19: 2898-2912. First Published on September 14, 2007; doi:10.1105/tpc.107.053611

This study presents the three-dimensional structures of AvrL567-A and AvrL567-D, two avirulence proteins from the flax rust pathogen that interact with resistance proteins L5, L6, and L7 from flax. Amino acid residues conferring recognition differences were tested by site-directed mutagenesis and suggest that the specificity of interaction results from the cumulative effects of multiple amino acid contacts.

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

Functional Dissection of Naturally Occurring Amino Acid Substitutions in eIF4E That Confers Recessive Potyvirus Resistance in Plants Inhwa Yeam, Jason R. Cavatorta, Daniel R. Ripoll, Byoung-Cheorl Kang, and Molly M. Jahn Plant Cell 2007 19: 2913-2928. First Published on September 21, 2007; doi:10.1105/tpc.107.050997 This study details the biological consequences and potential biochemical roles of amino acid substitutions in recessive resistance alleles at the Capsicum pvr1 locus encoding eIF4E. A Gly-to-Arg change at position 107 in the eIF4E protein encoded by multiple recessive resistance genes from diverse plants defines the most significant position for resistance to potyviruses. [Abstract] [Full Text] [PDF] [Supplemental Data] OPEN ACCESS ARTICLE

A Cluster of Disease Resistance Genes in Arabidopsis Is Coordinately Regulated by Transcriptional Activation and RNA Silencing

Hankuil Yi and Eric J. Richards

Plant Cell 2007 19: 2929-2939. First Published on September 21, 2007; doi:10.1105/tpc.107.051821

In the flowering plant Arabidopsis, genes encoding pathogen defense proteins are often clustered in the genome. This study shows that the genes in one cluster are coordinately regulated by a positive feed-forward transcriptional signaling loop and negative regulation via RNA silencing. Plant pathogens that suppress RNA silencing might trigger expression of these defense genes.

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

Rice Pti1a Negatively Regulates RAR1-Dependent Defense Responses Akira Takahashi, Ganesh Kumar Agrawal, Muneo Yamazaki, Katsura Onosato, Akio Miyao, Tsutomu Kawasaki, Ko Shimamoto, and Hirohiko Hirochika Plant Cell 2007 19: 2940-2951. First Published on September 21, 2007; doi:10.1105/tpc.106.047142 Several recent reports suggest that gene-for-gene and basal resistance signaling pathways substantially share common regulatory components. This work shows that Os Pti1a, a rice homolog of tomato Pti1, negatively regulates both resistance signaling pathways in rice and that its function depends on RAR1, which is known to function as a molecular chaperone in disease resistance. [Abstract] [Full Text] [PDF] [Supplemental Data] OPEN ACCESS ARTICLE

The Arabidopsis E3 SUMO Ligase SIZ1 Regulates Plant Growth and Drought Responses

Rafael Catala, Jian Ouyang, Isabel A. Abreu, Yuxin Hu, Haksoo Seo, Xiuren Zhang, and Nam-Hai Chua

Plant Cell 2007 19: 2952-2966. First Published on September 28, 2007; doi:10.1105/tpc.106.049981

Arabidopsis siz1 mutants are smaller in stature and have lower tolerance to drought stress than the wild type. Gene expression analysis shows that SIZ1 mediates the expression of 300 drought-inducible genes independently of DREB2A and ABA. The authors conclude that the SIZ1 SUMO E3 ligase plays a role in the regulation of gene expression that influences plant growth and the drought stress response.

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

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