IN THIS ISSUE:

Light Regulation of Plant Development: HY5 Genomic Binding Sites

Nancy A. Eckardt

Plant Cell 2007 19: 727-729.

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IN BRIEF:

Novel Oxylipin Signaling Cascades

Nancy A. Eckardt

Plant Cell 2007 19: 730.

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Focus on Meiotic Crossover Interference

Nancy A. Eckardt

Plant Cell 2007 19: 730.

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RESEARCH ARTICLES:

Analysis of Transcription Factor HY5 Genomic Binding Sites Revealed Its Hierarchical Role in Light Regulation of Development

Jungeun Lee, Kun He, Viktor Stolc, Horim Lee, Pablo Figueroa, Ying Gao, Waraporn Tongprasit, Hongyu Zhao, Ilha Lee, and Xing Wang Deng

Plant Cell 2007 19: 731-749. First Published on March 2, 2007; 10.1105/tpc.106.047688

Light signals induce complex developmental programs in plants. The transcription factor HY5 acts downstream of multiple photoreceptors, but its target genes are not well known. Putative HY5 binding sites were mapped to 3894 genes with diverse developmental functions, including early light-responsive genes. HY5 appears to be an early regulator of the transcriptional cascades for photomorphogenesis.

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

Elaboration of B Gene Function to Include the Identity of Novel Floral Organs in the Lower Eudicot Aquilegia

Elena M. Kramer, Lynn Holappa, Billie Gould, M. Alejandra Jaramillo, Dimitriy Setnikov, and Philip M. Santiago

Plant Cell 2007 19: 750-766. First Published on March 30, 2007; 10.1105/tpc.107.050385

The classical ABC model postulates three functionally overlapping classes of gene activity to establish the identity of four organ types, but some plants, such as Aquilegia, exhibit variation in floral organ identity that suggests a more complex ABC program. Expression and yeast two-hybrid analyses as well as gene silencing reveal that canonical B class function has been elaborated in Aquilegia.

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

TERMINAL FLOWER1 Is a Mobile Signal Controlling Arabidopsis Architecture

Lucio Conti and Desmond Bradley

Plant Cell 2007 19: 767-778. First Published on March 16, 2007; 10.1105/tpc.106.049767

TERMINAL FLOWER1 (TFL1) affects the number and identity of aerial organs. TFL1 mRNA is restricted to the inner cells of the meristem, but this work reveals that the protein is a mobile signal that becomes evenly distributed across the meristem and suggests a model for how floral and shoot meristems establish a feedback loop of expression and protein movement to control inflorescence architecture.

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

Single Gene–Mediated Shift in Pollinator Attraction in Petunia

Maria Elena Hoballah, Thomas Gübitz, Jeroen Stuurman, Larissa Broger, Mario Barone, Therese Mandel, Alexandre Dell'Olivo, Maeva Arnold, and Cris Kuhlemeier

Plant Cell 2007 19: 779-790. First Published on March 2, 2007; 10.1105/tpc.106.048694

Many floral traits appear to be adapted to particular pollinators. AN2 is a well-defined myb-type transcription factor that is a major determinant of flower color variation between two Petunia species. Transformation of one species with AN2 from the other caused a switch in pollinator preference, suggesting that adaptation to a new pollinator may involve a limited number of genes of large effect.

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

Seed Germination of GA-Insensitive sleepy1 Mutants Does Not Require RGL2 Protein Disappearance in Arabidopsis

Tohru Ariizumi and Camille M. Steber

Plant Cell 2007 19: 791-804. First Published on March 23, 2007; 10.1105/tpc.106.048009

Proper regulation of seed dormancy and germination is critical to plant survival. It was thought that disappearance of the negative regulator RGA-LIKE2 (RGL2) protein is required for seed germination. This report finds instead that RGL2 accumulates in germinating sleepy1 (sly1) mutants, suggesting that protein disappearance is not the only mechanism that relieves RGL2 repression of seed germination.

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The Mitogen-Activated Protein Kinase Cascade MKK3–MPK6 Is an Important Part of the Jasmonate Signal Transduction Pathway in Arabidopsis Fuminori Takahashi, Riichiro Yoshida, Kazuya Ichimura, Tsuyoshi Mizoguchi, Shigemi Seo, Masahiro Yonezawa, Kyonoshin Maruyama, Kazuko Yamaguchi-Shinozaki, and Kazuo Shinozaki Plant Cell 2007 19: 805-818. First Published on March 16, 2007; 10.1105/tpc.106.046581 The hormone jasmonic acid (JA) functions in stress responses and plant development. This work identified the mitogen-activated protein kinase cascade, MKK3–MPK6, which is activated by JA, and indicates key roles for this kinase unit in the JA signaling pathway in processes such as root growth and negative regulation of the transcriptional activator ATMYC2. [Abstract] [Full Text] [PDF] [Supplemental Data] OPEN ACCESS ARTICLE

The Antagonist Function of Arabidopsis WRKY53 and ESR/ESP in Leaf Senescence Is Modulated by the Jasmonic and Salicylic Acid Equilibrium

Ying Miao and Ulrike Zentgraf

Plant Cell 2007 19: 819-830. First Published on March 16, 2007; 10.1105/tpc.106.042705

Crosstalk between salicylic acid (SA) and jasmonic acid (JA) in leaf senescence is not well-known. This work shows that the senescence-specific transcription factor WRKY53 is positively regulated by SA and negatively by JA signaling and that the antagonistically regulated EPITHIOSPECIFYING SENESCENCE REGULATOR functions in the cytoplasm in nitrile biosynthesis but in the nucleus as an interaction partner with WRKY53.

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Oxylipins Produced by the 9-Lipoxygenase Pathway in Arabidopsis Regulate Lateral Root Development and Defense Responses through a Specific Signaling Cascade

Tamara Vellosillo, Marta Martínez, Miguel Angel López, Jorge Vicente, Tomas Cascón, Liam Dolan, Mats Hamberg, and Carmen Castresana

Plant Cell 2007 19: 831-846. First Published on March 16, 2007; 10.1105/tpc.106.046052

The importance of oxylipins, such as jasmonic acid, in plant defense and adaptation is well known. This work suggests that other oxylipins, such as 9-hydroxyoctadecatrienoic acid, also function in developmental and defense responses, such as callose and pectin deposition and production of reactive oxygen species. Mutant analyses revealed at least three signaling cascades mediating oxylipin action.

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

Rice UDP-Glucose Pyrophosphorylase1 Is Essential for Pollen Callose Deposition and Its Cosuppression Results in a New Type of Thermosensitive Genic Male Sterility Rongzhi Chen, Xiao Zhao, Zhe Shao, Zhe Wei, Yuanyuan Wang, Lili Zhu, Jie Zhao, Mengxiang Sun, Ruifeng He, and Guangcun He Plant Cell 2007 19: 847-861. First Published on March 30, 2007; 10.1105/tpc.106.044123 UDP-glucose pyrophosphorylase functions in carbohydrate metabolism and cell wall biosynthesis. Silencing of rice Ugp1 affects normal callose deposition during pollen mother cell (PMC) meiosis and leads to the degeneration of PMC at the early meiosis stage. This work demonstrates that rice Ugp1 is essential for PMC meiosis and microspore development. [Abstract] [Full Text] [PDF] [Supplemental Data] OPEN ACCESS ARTICLE

The Mismatch Repair Protein MLH1 Marks a Subset of Strongly Interfering Crossovers in Tomato Franck G.P. Lhuissier, Hildo H. Offenberg, Peter E. Wittich, Norbert O.E. Vischer, and Christa Heyting Plant Cell 2007 19: 862-876. First Published on March 2, 2007; 10.1105/tpc.106.049106 During meiosis, crossovers (COs) occur between homologous chromosomes, and CO positions are marked by protein complexes named late recombination nodules (LNs). This study shows that the mismatch repair protein MLH1 occurs in a specific subset of LNs and maps the chromosomal positions of the MLH1 foci. The maps of MLH1 foci and LNs could be valuable in various applications, including hybrid genetics. [Abstract] [Full Text] [PDF] [Supplemental Data] OPEN ACCESS ARTICLE

Arabidopsis MICROTUBULE-ASSOCIATED PROTEIN18 Functions in Directional Cell Growth by Destabilizing Cortical Microtubules

Xia Wang, Lei Zhu, Baoquan Liu, Che Wang, Lifeng Jin, Qian Zhao, and Ming Yuan

Plant Cell 2007 19: 877-889. First Published on March 2, 2007; 10.1105/tpc.106.048579

Mutations in microtubule-associated proteins (MAPs) result in abnormal plant development and plant cell morphogenesis due to disruption of microtubule (MT) organization. This study identified Arabidopsis MAP18, which binds to microtubules and inhibits tubulin polymerization, destabilizes MTs, and plays an important role in the regulation of MT organization to determine directional plant cell growth.

[Abstract] [Full Text] [PDF]

Impairment of Cellulose Synthases Required for Arabidopsis Secondary Cell Wall Formation Enhances Disease Resistance

Camilo Hernández-Blanco, Dong Xin Feng, Jian Hu, Andrea Sánchez-Vallet, Laurent Deslandes, Francisco Llorente, Marta Berrocal-Lobo, Harald Keller, Xavier Barlet, Clara Sánchez-Rodríguez, Lisa K. Anderson, Shauna Somerville, Yves Marco, and Antonio Molina

Plant Cell 2007 19: 890-903. First Published on March 9, 2007; 10.1105/tpc.106.048058

Mutations in cellulose synthase subunits required for secondary cell wall formation confer resistance to bacterial and fungal pathogens and upregulate ABA-responsive defense genes. Alteration of secondary cell wall integrity by inhibiting cellulose synthesis may lead to activation of novel defense pathways that create antimicrobial-enriched environments hostile to pathogens.

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

A Core Subunit of the RNA-Processing/Degrading Exosome Specifically Influences Cuticular Wax Biosynthesis in Arabidopsis

Tanya S. Hooker, Patricia Lam, Huanquan Zheng, and Ljerka Kunst

Plant Cell 2007 19: 904-913. First Published on March 9, 2007; 10.1105/tpc.106.049304

The cuticle, an extracellular matrix of cutin polyester and waxes, covers and protects plant aerial organs, but little is known about the regulation of cuticular wax deposition. Mutant analysis and gene isolation and characterization demonstrate that wax production is controlled, at least in part, by the mRNA stability of a repressor that is recognized and degraded by the CER7 ribonuclease.

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

The N-Terminal Double-Stranded RNA Binding Domains of Arabidopsis HYPONASTIC LEAVES1 Are Sufficient for Pre-MicroRNA Processing

Feijie Wu, Lin Yu, Wenguang Cao, Yanfei Mao, Zhongyuan Liu, and Yuke He

Plant Cell 2007 19: 914-925. First Published on March 2, 2007; 10.1105/tpc.106.048637

Some double-stranded RNA binding proteins participate in miRNA biogenesis. A series of deletion mutants demonstrated that the N-terminal region of HYPONASTIC LEAVES1 with two double-stranded RNA binding domains is sufficient for miRNA biogenesis and capable of rescuing the hyl1 phenotype. This study also showed that the putative NLS is a true nuclear localization signal.

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

Genome-Wide Analysis of the RNA-DEPENDENT RNA POLYMERASE6/DICER-LIKE4 Pathway in Arabidopsis Reveals Dependency on miRNA- and tasiRNA-Directed Targeting Miya D. Howell, Noah Fahlgren, Elisabeth J. Chapman, Jason S. Cumbie, Christopher M. Sullivan, Scott A. Givan, Kristin D. Kasschau, and James C. Carrington Plant Cell 2007 19: 926-942. First Published on March 30, 2007; 10.1105/tpc.107.050062 Using high-throughput sequencing methods, many transcripts were found to be routed through the RDR6/DCL4-dependent silencing pathway after single or dual targeting events by miRNA or tasiRNA. Several members of a rapidly expanding clade of PPR gene transcripts were targeted, suggesting that this silencing pathway may function to buffer the effects of rapidly expanding gene families. [Abstract] [Full Text] [PDF] OPEN ACCESS ARTICLE

Improperly Terminated, Unpolyadenylated mRNA of Sense Transgenes Is Targeted by RDR6-Mediated RNA Silencing in Arabidopsis

Zhenghua Luo and Zhixiang Chen

Plant Cell 2007 19: 943-958. First Published on March 23, 2007; 10.1105/tpc.106.045724

RNA silencing induced by sense transgenes may protect against excessively expressed genes, but whether all transcripts or just aberrant ones activate genome surveillance is unclear. Constructs with enhanced or reduced production of aberrant RNAs were tested and showed RNA-DEPENDENT RNA POLYMERASE6–mediated silencing induced by aberrant mRNAs, which probably act as templates for the RNA polymerase.

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

Arabidopsis Phage-Type RNA Polymerases: Accurate in Vitro Transcription of Organellar Genes

Kristina Kühn, Alexandra-Viola Bohne, Karsten Liere, Andreas Weihe, and Thomas Börner

Plant Cell 2007 19: 959-971. First Published on March 30, 2007; 10.1105/tpc.106.046839

Three Arabidopsis nuclear-encoded T7 phage-type RNA polymerases (RNAPs) localize to mitochondria, plastids, or both. This study finds that two of them can initiate transcription from both mitochondrial and plastid promoters in vitro without auxiliary factors. The ability for promoter recognition appears to have been conserved over a long period of evolution of organellar RNAPs.

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

T-Loop Phosphorylation of Arabidopsis CDKA;1 Is Required for Its Function and Can Be Partially Substituted by an Aspartate Residue Nico Dissmeyer, Moritz K. Nowack, Stefan Pusch, Hilde Stals, Dirk Inzé, Paul E. Grini, and Arp Schnittger Plant Cell 2007 19: 972-985. First Published on March 16, 2007; 10.1105/tpc.107.050401 To divide or not is one of the most crucial choices made by cells. As in other eukaryotes, progression through the cell cycle in plants is governed by cyclin-dependent kinases (CDKs), and one of the major regulatory inputs to CDK function is phosphorylation. Here, it is shown that Arabidopsis CDKA;1 is phosphorylated in the T-loop region and that phosphorylation is essential for kinase function. [Abstract] [Full Text] [PDF] [Supplemental Data] OPEN ACCESS ARTICLE

PIC1, an Ancient Permease in Arabidopsis Chloroplasts, Mediates Iron Transport

Daniela Duy, Gerhard Wanner, Anderson R. Meda, Nicolaus von Wirén, Jürgen Soll, and Katrin Philippar

Plant Cell 2007 19: 986-1006. First Published on March 2, 2007; 10.1105/tpc.106.047407

Chloroplasts are a major sink for metal ions like iron and copper, which play essential roles in photosynthetic electron transport. However, very little is known about iron uptake by the chloroplast. This study characterized PIC1 from Arabidopsis, which is a transmembrane protein of cyanobacterial origin that most likely functions as a metal ion permease in the chloroplast envelope.

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

Chlorophyllase Is a Rate-Limiting Enzyme in Chlorophyll Catabolism and Is Posttranslationally Regulated

Smadar Harpaz-Saad, Tamar Azoulay, Tzahi Arazi, Eran Ben-Yaakov, Anahit Mett, Yoel M. Shiboleth, Stefan Hörtensteiner, David Gidoni, Amit Gal-On, Eliezer E. Goldschmidt, and Yoram Eyal

Plant Cell 2007 19: 1007-1022. First Published on March 16, 2007; 10.1105/tpc.107.050633

Chlorophyll is a central player in photosynthetic light harvesting, but details of chlorophyll catabolism and regulation are unresolved. Here, two different expression systems in two species were used to study the role and regulation of Chlase in chlorophyll catabolism. The results suggest that Chlase is a rate-limiting enzyme in chlorophyll catabolism controlled via posttranslational regulation.

[Abstract] [Full Text] [PDF]

Integration of Chloroplast Nucleic Acid Metabolism into the Phosphate Deprivation Response in Chlamydomonas reinhardtii Shlomit Yehudai-Resheff, Sara L. Zimmer, Yutaka Komine, and David B. Stern Plant Cell 2007 19: 1023-1038. First Published on March 9, 2007; 10.1105/tpc.106.045427 The role of the chloroplast as a phosphorus (P) reservoir in acclimation to P limitation is not well known. Polynucleotide phosphorylase consumes P through RNA decay, and while P deprivation usually stimulates RNA decay, in Chlamydomonas chloroplasts RNA levels rise but DNA levels fall during acclimation, suggesting that chloroplast polyploidy may be adaptive as a repository for P. [Abstract] [Full Text] [PDF] OPEN ACCESS ARTICLE

The Thylakoid Lumen Protease Deg1 Is Involved in the Repair of Photosystem II from Photoinhibition in Arabidopsis

Einat Kapri-Pardes, Leah Naveh, and Zach Adam

Plant Cell 2007 19: 1039-1047. First Published on March 9, 2007; 10.1105/tpc.106.046573

Photosynthesis is accompanied by accumulation of highly oxidizing species and oxygen radicals that cause photodamage within the photosystem II complex. Removal of damaged copies of the D1 protein is a prerequisite for reassembly of this complex. RNAi mutant and other analyses suggest that the lumenal protease Deg1 is involved in degradation of the D1 protein during PSII repair from photoinhibition.

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

The Arabidopsis aba4-1 Mutant Reveals a Specific Function for Neoxanthin in Protection against Photooxidative Stress

Luca Dall'Osto, Stefano Cazzaniga, Helen North, Annie Marion-Poll, and Roberto Bassi

Plant Cell 2007 19: 1048-1064. First Published on March 9, 2007; 10.1105/tpc.106.049114

Carotenoids help protect the chloroplast from photoxidative stress. The aba4-1 mutant lacks neoxanthin but retains all other xanthophyll species. This research shows that neoxanthin plays a specific role in protection of Lhc proteins, the PSII reaction center, and thylakoids from photooxidative stress and protects against the damaging effects of reactive oxygen species, particularly superoxide anions.

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

Calcium-Dependent Protein Kinases Regulate the Production of Reactive Oxygen Species by Potato NADPH Oxidase Michie Kobayashi, Ikuko Ohura, Kazuhito Kawakita, Naohiko Yokota, Masayuki Fujiwara, Ko Shimamoto, Noriyuki Doke, and Hirofumi Yoshioka Plant Cell 2007 19: 1065-1080. First Published on March 30, 2007; 10.1105/tpc.106.048884 The NADPH oxidase RBOH and calcium-dependent protein kinases (CDPKs) are implicated in rapid production of reactive oxygen species, or oxidative burst, early in plant–pathogen interactions, but the regulatory mechanisms are unknown. The results of this work suggest that Ca2+-dependent phosphorylation of potato RBOHB by CDPK5 plays a central role in oxidative burst during pathogen infection. [Abstract] [Full Text] [PDF] [Supplemental Data] OPEN ACCESS ARTICLE

Death Don't Have No Mercy and Neither Does Calcium: Arabidopsis CYCLIC NUCLEOTIDE GATED CHANNEL2 and Innate Immunity

Rashid Ali, Wei Ma, Fouad Lemtiri-Chlieh, Dimitrios Tsaltas, Qiang Leng, Susannne von Bodman, and Gerald A. Berkowitz

Plant Cell 2007 19: 1081-1095. First Published on March 23, 2007; 10.1105/tpc.106.045096

Plants lacking a Ca²⁺-conducting channel do not undergo hypersensitive response to pathogens and have impaired nitric oxide generation in response to application of a pathogen-associated molecular pattern elicitor. Patch clamp analysis demonstrated elicitor activation of inward cation currents; this work provides insights regarding early steps in pathogen response signaling in plants.

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

Herbivory Rapidly Activates MAPK Signaling in Attacked and Unattacked Leaf Regions but Not between Leaves of Nicotiana attenuata

Jianqiang Wu, Christian Hettenhausen, Stefan Meldau, and Ian T. Baldwin

Plant Cell 2007 19: 1096-1122. First Published on March 30, 2007; 10.1105/tpc.106.049353

Mitogen-activated protein kinase (MAPK) signaling mediates plant responses to herbivore attack, but the transduction of these signals is poorly understood. This work examines how plants deploy defense reactions and demonstrates that herbivore oral secretions (OS) dramatically amplify wound-induced MAPK activity and that fatty acid–amino acid conjugates in herbivore OS are the elicitors.

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

A Mutant of the Arabidopsis Phosphate Transporter PHT1;1 Displays Enhanced Arsenic Accumulation

Pablo Catarecha, M^a Dolores Segura, José Manuel Franco-Zorrilla, Berenice García-Ponce, Mónica Lanza, Roberto Solano, Javier Paz-Ares, and Antonio Leyva

Plant Cell 2007 19: 1123-1133. First Published on March 30, 2007; 10.1105/tpc.106.041871

Arsenate [As(V)], the most abundant chemical form of the toxic element arsenic, is very similar to phosphate (Pi), which enables its uptake from the soil through the high-affinity Pi transport system. This work identifies a Pi transporter mutant with enhanced ability to accumulate arsenic but with a reduced Pi and As(V) uptake rate, suggesting a protective mechanism operating in arsenic-tolerant plants.

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