EDITORIAL:

The Freedom to Innovate: A Privilege or a Right?

Rich Jorgensen

Plant Cell 2007 19: 1433-1434. First Published on May 31, 2007; 10.1105/tpc.107.190580

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IN THIS ISSUE:

Phloem-Borne FT Signals Flowering in Cucurbits

Nancy A. Eckardt

Plant Cell 2007 19: 1435-1438.

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IN BRIEF:

A CLASSY RNA Silencing Signaling Mutant in Arabidopsis

Nancy A. Eckardt

Plant Cell 2007 19: 1439.

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Bigfoot Genes and Plant Response to Environmental Change

Nancy A. Eckardt

Plant Cell 2007 19: 1439.

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RESEARCH ARTICLES:

G-Boxes, Bigfoot Genes, and Environmental Response: Characterization of Intragenomic Conserved Noncoding Sequences in Arabidopsis

Michael Freeling, Lakshmi Rapaka, Eric Lyons, Brent Pedersen, and Brian C. Thomas

Plant Cell 2007 19: 1441-1457. First Published on May 11, 2007; 10.1105/tpc.107.050419

Arabidopsis genes that encode transcription factors, and especially those that respond to signals, tend to have many conserved noncoding sequences (CNSs) around them. These CNS footprints sometimes contain known transcription factor binding motifs, like G-boxes, and sometimes these motifs are strand specific, but CNSs are best characterized by the sequences they are not.

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

The Two AGPase Subunits Evolve at Different Rates in Angiosperms, yet They Are Equally Sensitive to Activity-Altering Amino Acid Changes When Expressed in Bacteria

Nikolaos Georgelis, Edward L. Braun, Janine R. Shaw, and L. Curtis Hannah

Plant Cell 2007 19: 1458-1472. First Published on May 11, 2007; 10.1105/tpc.106.049676

ADP-glucose pyrophosphorylase small subunits in angiosperms are under greater selection pressure than large subunits. Yet, the two subunits are equally susceptible to activity-altering substitutions when expressed in E. coli. This work suggests that the small subunit has more evolutionary constraints because it is less tissue specific and must form enzyme complexes with different large subunits.

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

CYP703 Is an Ancient Cytochrome P450 in Land Plants Catalyzing in-Chain Hydroxylation of Lauric Acid to Provide Building Blocks for Sporopollenin Synthesis in Pollen

Marc Morant, Kirsten Jørgensen, Hubert Schaller, Franck Pinot, Birger Lindberg Møller, Danièle Werck-Reichhart, and Søren Bak

Plant Cell 2007 19: 1473-1487. First Published on May 11, 2007; 10.1105/tpc.106.045948

CYP703 is a conserved cytochrome P450 ubiquitously present in land plants. In Arabidopsis, CYP703A2 is exclusively expressed in developing anthers at the tetrad stage. Knockout of CYP703A2 results in pollen with an impaired surface and a partial male-sterile phenotype. CYP703A2 catalyzes in-chain hydroxylation of lauric acid and provides essential building blocks for sporopollenin synthesis.

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

FLOWERING LOCUS T Protein May Act as the Long-Distance Florigenic Signal in the Cucurbits

Ming-Kuem Lin, Helene Belanger, Young-Jin Lee, Erika Varkonyi-Gasic, Ken-Ichiro Taoka, Eriko Miura, Beatriz Xoconostle-Cázares, Karla Gendler, Richard A. Jorgensen, Brett Phinney, Tony J. Lough, and William J. Lucas

Plant Cell 2007 19: 1488-1506. First Published on May 31, 2007; 10.1105/tpc.107.051920

Photoperiodic floral initiation involves a leaf-derived signal, termed florigen, which is transported in the phloem and acted upon by meristematic cells within the shoot apex. Analysis of the phloem sap collected from photoperiodically induced and noninduced cucurbit species established that the presence of FT-like protein, but not FT-like mRNA, was highly correlated with the onset of flowering.

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

An SNF2 Protein Associated with Nuclear RNA Silencing and the Spread of a Silencing Signal between Cells in Arabidopsis Lisa M. Smith, Olga Pontes, Iain Searle, Nataliya Yelina, Faridoon K. Yousafzai, Alan J. Herr, Craig S. Pikaard, and David C. Baulcombe Plant Cell 2007 19: 1507-1521. First Published on May 25, 2007; 10.1105/tpc.107.051540 An RNA interference transgene with a phloem-specific promoter triggers a mobile signal and, consequently, silencing in cells adjacent to veins. The nuclear proteins CLASSY1 with SNF2 domain, RNA-DEPENDENT RNA POLYMERASE2, the RNA polymerase IVa subunit NRPD1a, and proteins associated with trans-acting short interfering RNAs are required for this phenotype. This combination of proteins indicates modularity of silencing pathways. [Abstract] [Full Text] [PDF] [Supplemental Data] OPEN ACCESS ARTICLE

TIME FOR COFFEE Encodes a Nuclear Regulator in the Arabidopsis thaliana Circadian Clock

Zhaojun Ding, Andrew J. Millar, Amanda M. Davis, and Seth J. Davis

Plant Cell 2007 19: 1522-1536. First Published on May 11, 2007; 10.1105/tpc.106.047241

The plant circadian clock is required for daily anticipation of the diurnal environment. The work presented here implicates TIME FOR COFFEE (TIC) as contributing a key role in the circadian clock, where it works close to the central oscillator of Arabidopsis. LATE ELONGATED HYPOCOTYL transcriptional induction is one target gene of TIC action.

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NUCLEAR PORE ANCHOR, the Arabidopsis Homolog of Tpr/Mlp1/Mlp2/Megator, Is Involved in mRNA Export and SUMO Homeostasis and Affects Diverse Aspects of Plant Development

Xianfeng Morgan Xu, Annkatrin Rose, Sivaramakrishnan Muthuswamy, Sun Yong Jeong, Sowmya Venkatakrishnan, Qiao Zhao, and Iris Meier

Plant Cell 2007 19: 1537-1548. First Published on May 18, 2007; 10.1105/tpc.106.049239

Plant nuclear pore complexes, vital for information exchange between nucleus and cytoplasm, have been implied in plant-microbe interaction, hormone signaling, and stress tolerance. Here, developmental and molecular mutant phenotypes of NUCLEAR PORE ANCHOR, the plant homolog of mammalian and yeast inner nuclear pore proteins, suggest a potential link between the SUMO pathway and mRNA metabolism in plants.

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

Components of the Arabidopsis mRNA Decapping Complex Are Required for Early Seedling Development

David C. Goeres, Jaimie M. Van Norman, Weiping Zhang, Nellie A. Fauver, Mary Lou Spencer, and Leslie E. Sieburth

Plant Cell 2007 19: 1549-1564. First Published on May 18, 2007; 10.1105/tpc.106.047621

RNA decay can be important for responses to both developmental and environmental signals. Analysis of trident and varicose mutants reveals that the loss of mRNA decapping results in pleiotropic early seedling defects and suggests that the developmental transition to early seedling development is particularly sensitive to mRNA decapping defects.

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

UDP-Glucose 4-Epimerase Isoforms UGE2 and UGE4 Cooperate in Providing UDP-Galactose for Cell Wall Biosynthesis and Growth of Arabidopsis thaliana Johannes Rösti, Christopher J. Barton, Sandra Albrecht, Paul Dupree, Markus Pauly, Kim Findlay, Keith Roberts, and Georg J. Seifert Plant Cell 2007 19: 1565-1579. First Published on May 11, 2007; 10.1105/tpc.106.049619 Five Arabidopsis genes encode UDP-glucose 4-epimerase (UGE) and represent two ancient UGE clades. This reverse genetic study tests the hypothesis that they might be involved in regulation of cell wall carbohydrate biosynthesis. The results suggest a gradual specialization of UGE isoforms throughout plant evolution, which is likely to involve transcriptional and cellular mechanisms. [Abstract] [Full Text] [PDF] [Supplemental Data] OPEN ACCESS ARTICLE

Structure and Function of a Mitochondrial Late Embryogenesis Abundant Protein Are Revealed by Desiccation

Dimitri Tolleter, Michel Jaquinod, Cécile Mangavel, Catherine Passirani, Patrick Saulnier, Stephen Manon, Emeline Teyssier, Nicole Payet, Marie-Hélène Avelange-Macherel, and David Macherel

Plant Cell 2007 19: 1580-1589. First Published on May 25, 2007; 10.1105/tpc.107.050104

This report provides clues about the structure and function of a seed mitochondrial protein (LEAM). LEAM appears unstructured in solution but reversibly folds upon drying into an amphipathic helical form reminiscent of apolipoproteins. Overall, data support a model in which the helical LEAM inserts into the membrane parallel to its plane, providing structural reinforcement in the dry state.

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

The Arabidopsis ATNRT2.7 Nitrate Transporter Controls Nitrate Content in Seeds

Franck Chopin, Mathilde Orsel, Marie-France Dorbe, Fabien Chardon, Hoai-Nam Truong, Anthony J. Miller, Anne Krapp, and Françoise Daniel-Vedele

Plant Cell 2007 19: 1590-1602. First Published on May 31, 2007; 10.1105/tpc.107.050542

Sugars, lipids, and proteins are the main reserves, but minerals are also stored in seed vacuoles. Nitrate stored in the seed has osmotic, nutritional, and signaling roles. This work shows that in Arabidopsis thaliana, the seed storage of nitrate is mediated in part by the high-affinity transporter NRT2.7. A defect in this gene leads to a lower seed nitrate content and higher seed dormancy.

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

Increasing Plasma Membrane Phosphatidylinositol(4,5)Bisphosphate Biosynthesis Increases Phosphoinositide Metabolism in Nicotiana tabacum Yang Ju Im, Imara Y. Perera, Irena Brglez, Amanda J. Davis, Jill Stevenson-Paulik, Brian Q. Phillippy, Eva Johannes, Nina S. Allen, and Wendy F. Boss Plant Cell 2007 19: 1603-1616. First Published on May 11, 2007; 10.1105/tpc.107.051367 Inositol phospholipids are important in cell signaling and plant growth. A genetic approach was used to test the hypothesis that phosphorylation of PtdIns(4)P to PtdIns(4,5)P2 is limiting in plant phosphoinositide (PI) metabolism. The results demonstrate that PtdInsP kinase is flux limiting in these cells and reveal that a high rate of PI metabolism increases the energy demands on the cells. [Abstract] [Full Text] [PDF] [Supplemental Data] OPEN ACCESS ARTICLE

Arabidopsis Protein Kinase PKS5 Inhibits the Plasma Membrane H⁺-ATPase by Preventing Interaction with 14-3-3 Protein

Anja T. Fuglsang, Yan Guo, Tracey A. Cuin, Quansheng Qiu, Chunpeng Song, Kim A. Kristiansen, Katrine Bych, Alexander Schulz, Sergey Shabala, Karen S. Schumaker, Michael G. Palmgren, and Jian-Kang Zhu

Plant Cell 2007 19: 1617-1634. First Published on May 4, 2007; 10.1105/tpc.105.035626

Plants have to cope with numerous environmental challenges, such as constantly changing soil pH. This work identifies a Ser/Thr protein kinase, PKS5, which interacts with the calcium binding protein SCaBP1 and shows that high external pH can trigger an increase in cytosolic-free calcium, suggesting that PKS5 is part of a calcium-signaling pathway mediating plasma membrane H⁺-ATPase regulation.

[Abstract] [Full Text] [PDF]

Canonical Signal Recognition Particle Components Can Be Bypassed for Posttranslational Protein Targeting in Chloroplasts

Tzvetelina Tzvetkova-Chevolleau, Claire Hutin, Laurent D. Noël, Robyn Goforth, Jean-Pierre Carde, Stephano Caffarri, Irmgard Sinning, Matthew Groves, Jean-Marie Teulon, Neil E. Hoffman, Ralph Henry, Michel Havaux, and Laurent Nussaume

Plant Cell 2007 19: 1635-1648. First Published on May 18, 2007; 10.1105/tpc.106.048959

The chloroplast signal recognition particle (cpSRP) and its receptor (cpFtsY) target nuclear-encoded light-harvesting chlorophyll binding proteins (LHCPs) to the thylakoids. However, mutant analyses in this work demonstrate an alternative targeting mechanism that most likely relies on cpSRP43 and its ability to bind both LHCP and the translocase ALBINO3.

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

The Senescence-Induced Staygreen Protein Regulates Chlorophyll Degradation

So-Yon Park, Jae-Woong Yu, Jong-Sung Park, Jinjie Li, Soo-Cheul Yoo, Na-Yeoun Lee, Sang-Kyu Lee, Seok-Won Jeong, Hak Soo Seo, Hee-Jong Koh, Jong-Seong Jeon, Youn-Il Park, and Nam-Chon Paek

Plant Cell 2007 19: 1649-1664. First Published on May 18, 2007; 10.1105/tpc.106.044891

Color change occurs during leaf senescence or accelerated cell death. This analysis of the staygreen mutant indicates that retention of green color in the mutant is associated with a failure to destabilize the light-harvesting chlorophyll (Chl) binding protein (LHCP) complexes of the thylakoid membranes, which is a prerequisite for the degradation of Chls and LHCPs during senescence.

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

ABA Is an Essential Signal for Plant Resistance to Pathogens Affecting JA Biosynthesis and the Activation of Defenses in Arabidopsis

Bruce A.T. Adie, Julián Pérez-Pérez, Manuel M. Pérez-Pérez, Marta Godoy, José-J. Sánchez-Serrano, Eric A. Schmelz, and Roberto Solano

Plant Cell 2007 19: 1665-1681. First Published on May 18, 2007; 10.1105/tpc.106.048041

Contact with a pathogen leads to the induction of a multitude of defenses. This study of the Arabidopsis–Pythium irregulare fungal infection process and defense pathways indicates that abscisic acid (ABA) is a component of the signaling network activating plant defenses necessary for resistance against some necrotrophic pathogens and that ABA levels may be key to the fine-tuning of plant defenses.

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

Physical Association of the NB-LRR Resistance Protein Rx with a Ran GTPase–Activating Protein Is Required for Extreme Resistance to Potato virus X Wladimir I.L. Tameling and David C. Baulcombe Plant Cell 2007 19: 1682-1694. First Published on May 25, 2007; 10.1105/tpc.107.050880 Nucleotide binding leucine-rich repeat (NB-LRR) resistance (R) proteins recognize specific pathogen-derived effectors. This work shows that Ran GTPase Activating Protein (RanGAP) and NB-LRR protein Rx interaction is required for resistance to Potato virus X and suggests that RanGAP2 is part of the Rx signaling complex and that Rx-mediated virus resistance involves protein transport into the nucleus. [Abstract] [Full Text] [PDF] [Supplemental Data] OPEN ACCESS ARTICLE

Arabidopsis VIRE2 INTERACTING PROTEIN2 Is Required for Agrobacterium T-DNA Integration in Plants

Ajith Anand, Alexander Krichevsky, Sebastian Schornack, Thomas Lahaye, Tzvi Tzfira, Yuhong Tang, Vitaly Citovsky, and Kirankumar S. Mysore

Plant Cell 2007 19: 1695-1708. First Published on May 11, 2007; 10.1105/tpc.106.042903

Agrobacterium-mediated genetic transformation offers an efficient tool for genetic engineering of plants. VirE2 is an Agrobacterium protein that presumably protects T-DNA from degradation. This work identifies Arabidopsis VIRE2-INTERACTING PROTEIN2 (VIP2) that is required for stable, but not transient, transformation and interacts with VIP1, which is required for nuclear import and T-DNA integration.

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

Tomato BRASSINOSTEROID INSENSITIVE1 Is Required for Systemin-Induced Root Elongation in Solanum pimpinellifolium but Is Not Essential for Wound Signaling

Nicholas Holton, Ana Caño-Delgado, Kate Harrison, Teresa Montoya, Joanne Chory, and Gerard J. Bishop

Plant Cell 2007 19: 1709-1717. First Published on May 18, 2007; 10.1105/tpc.106.047795

Brassinosteroids (BRs) are hormones required for normal growth and development, and systemin is a peptide involved in wound response. Tomato BRI1 has previously been implicated in both systemin and BR signaling, and this work confirms its role in BR signaling but indicates that it is not essential for systemin wound signaling, although in certain species, it may promote root growth.

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

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