EDITORIAL:

New Features for a New Year

Rich Jorgensen

Plant Cell 2007 19: 1. First Published on January 12, 2007; 10.1105/tpc.107.190180

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IN THIS ISSUE:

Gibberellins Are Modified by Methylation in Planta

Nancy A. Eckardt

Plant Cell 2007 19: 3-6.

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IN BRIEF:

A Complete MAPK Signaling Cascade That Functions in Stomatal Development and Patterning in Arabidopsis

Nancy A. Eckardt

Plant Cell 2007 19: 7.

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Arabidopsis WEE1 Kinase Controls Cell Cycle Arrest in Response to DNA Damage

Nancy A. Eckardt

Plant Cell 2007 19: 7.

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RESEARCH ARTICLES:

SDG714, a Histone H3K9 Methyltransferase, Is Involved in Tos17 DNA Methylation and Transposition in Rice

Yong Ding, Xia Wang, Lei Su, JiXian Zhai, ShouYun Cao, DongFen Zhang, ChunYan Liu, YuPing Bi, Qian Qian, ZhuKuan Cheng, ChengCai Chu, and XiaoFeng Cao

Plant Cell 2007 19: 9-22. First Published on January 26, 2007; 10.1105/tpc.106.048124

Rice SDG714 encodes a histone H3K9 methyltransferase associated with heterochromatin. SDG714 is involved in macro trichome development and in DNA methylation, transposition of transposable elements, and genome stability in rice.

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

Regulation of Telomerase in Arabidopsis by BT2, an Apparent Target of TELOMERASE ACTIVATOR1 Shuxin Ren, Kranthi K. Mandadi, Amy L. Boedeker, Keerti S. Rathore, and Thomas D. McKnight Plant Cell 2007 19: 23-31. First Published on January 12, 2007; 10.1105/tpc.106.044321 Telomerase is developmentally regulated in plants. The Arabidopsis transcription factor TELOMERASE ACTIVATOR1 (TAC1) potentiates some responses to auxin, including induction of telomerase activity in leaves. The authors report that BT2 is an essential component of the TAC1-mediated telomerase activation pathway and acts downstream of TAC1 to regulate telomerase activity in mature vegetative organs. [Abstract] [Full Text] [PDF] OPEN ACCESS ARTICLE

Methylation of Gibberellins by Arabidopsis GAMT1 and GAMT2

Marina Varbanova, Shinjiro Yamaguchi, Yue Yang, Katherine McKelvey, Atsushi Hanada, Roy Borochov, Fei Yu, Yusuke Jikumaru, Jeannine Ross, Diego Cortes, Choong Je Ma, Joseph P. Noel, Lew Mander, Vladimir Shulaev, Yuji Kamiya, Steve Rodermel, David Weiss, and Eran Pichersky

Plant Cell 2007 19: 32-45. First Published on January 12, 2007; 10.1105/tpc.106.044602

Two Arabidopsis genes expressed during seed development are shown to encode enzymes that methylate various gibberellins to produce the respective methylesters, rendering them inactive and possibly targeting them for degradation. Gibberellins thus join jasmonic acid, salicylic acid, and auxin as plant signaling molecules known to be modified by methylation under some circumstances.

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The indeterminate gametophyte1 Gene of Maize Encodes a LOB Domain Protein Required for Embryo Sac and Leaf Development

Matthew M.S. Evans

Plant Cell 2007 19: 46-62. First Published on January 5, 2007; 10.1105/tpc.106.047506

The cloning of the maize ig1 gene and the phenotype of ig1 mutant leaves is reported here. ig1 leaves have disrupted polarity and ectopically express meristem-specific genes. The ig1 leaf phenotype suggests that early defects in embryo sac polarity lead to the abnormal morphology of ig1 embryo sacs and that common mechanisms promote differentiation in angiosperm leaves and embryo sacs.

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Stomatal Development and Patterning Are Regulated by Environmentally Responsive Mitogen-Activated Protein Kinases in Arabidopsis

Huachun Wang, Njabulo Ngwenyama, Yidong Liu, John C. Walker, and Shuqun Zhang

Plant Cell 2007 19: 63-73. First Published on January 26, 2007; 10.1105/tpc.106.048298

This study identifies MPK3/MPK6 and MKK4/MKK5 as key regulators of stomatal development and patterning that function downstream of MAPKKK YODA to coordinate cell fate specification.

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Repression of Flowering in Arabidopsis Requires Activation of FLOWERING LOCUS C Expression by the Histone Variant H2A.Z Roger B. Deal, Christopher N. Topp, Elizabeth C. McKinney, and Richard B. Meagher Plant Cell 2007 19: 74-83. First Published on January 12, 2007; 10.1105/tpc.106.048447 The two Arabidopsis proteins ARP6 and PIE1 are shown to be required for the deposition of histone H2A.Z into chromatin. Mutations in ARP6 and PIE1 cause early flowering due to reduced expression of the floral repressor gene FLC, indicating that the H2A.Z variant is required for high-level FLC expression. [Abstract] [Full Text] [PDF] [Supplemental Data] OPEN ACCESS ARTICLE

CRYPTOCHROME2 in Vascular Bundles Regulates Flowering in Arabidopsis

Motomu Endo, Nobuyoshi Mochizuki, Tomomi Suzuki, and Akira Nagatani

Plant Cell 2007 19: 84-93. First Published on January 26, 2007; 10.1105/tpc.106.048157

The phtotreceptors cry2 and phyB function in different tissues to regulate flowering. In contrast with phyB, which regulates flowering in the mesophyll by suppressing the expression of a flowering regulator, FLOWERING LOCUS T, cry2 functions in vascular bundles to promote expression of FT. The physical segregation of these photoreceptors may be a function of the availability of the appropriate light signals to these tissues.

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S Locus Genes and the Evolution of Self-Fertility in Arabidopsis thaliana

Sue Sherman-Broyles, Nathan Boggs, Agnes Farkas, Pei Liu, Julia Vrebalov, Mikhail E. Nasrallah, and June B. Nasrallah

Plant Cell 2007 19: 94-106. First Published on January 19, 2007; 10.1105/tpc.106.048199

Loss of self-incompatibility (SI) in A. thaliana was accompanied by inactivation of SRK and SCR, coadapted genes that comprise the SI specificity–determining S haplotype. Analysis of the C24 and Col-0 S haplotypes, and of S locus polymorphisms in 70 accessions, shows that the A. thaliana S locus has undergone extensive structural remodeling and argues against the occurrence of a selective sweep at SCR as previously suggested.

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Characterization of the SP11/SCR High-Affinity Binding Site Involved in Self/Nonself Recognition in Brassica Self-Incompatibility

Hiroko Shimosato, Naohiko Yokota, Hiroshi Shiba, Megumi Iwano, Tetsuyuki Entani, Fang-Sik Che, Masao Watanabe, Akira Isogai, and Seiji Takayama

Plant Cell 2007 19: 107-117. First Published on January 12, 2007; 10.1105/tpc.105.038869

Self-incompatibility in Brassica is initiated by haplotype-specific interactions between the pollen-borne ligand (SP11/SCR) and its stigmatic receptor kinase (SRK). This study shows that plasma membrane localization and subsequent homodimerization are essential for SRK to exhibit high-affinity binding to SP11/SCR.

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ARF7 and ARF19 Regulate Lateral Root Formation via Direct Activation of LBD/ASL Genes in Arabidopsis

Yoko Okushima, Hidehiro Fukaki, Makoto Onoda, Athanasios Theologis, and Masao Tasaka

Plant Cell 2007 19: 118-130. First Published on January 26, 2007; 10.1105/tpc.106.047761

Auxin-inducible LOB domain/AS2-like genes LBD16/ASL18 and LBD29/ASL16 were identified as direct targets of ARF7 and ARF19 transcription activators that regulate Arabidopsis lateral root formation. It is further shown that LBD16 functions positively in lateral root formation as a transcriptional regulator downstream of ARF7- and ARF19-dependent auxin signaling.

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Interactions among PIN-FORMED and P-Glycoprotein Auxin Transporters in Arabidopsis

Joshua J. Blakeslee, Anindita Bandyopadhyay, Ok Ran Lee, Jozef Mravec, Boosaree Titapiwatanakun, Michael Sauer, Srinivas N. Makam, Yan Cheng, Rodolphe Bouchard, Jirí Adamec, Markus Geisler, Akitomo Nagashima, Tatsuya Sakai, Enrico Martinoia, Jirí Friml, Wendy Ann Peer, and Angus S. Murphy

Plant Cell 2007 19: 131-147. First Published on January 19, 2007; 10.1105/tpc.106.040782

PINs and PGPs function in coordinated, independent auxin transport mechanisms, but also act synergistically in a tissue-specific manner, as specific PIN-PGP pairings influence polar auxin movement by enhancing substrate specificity and modulating rates of cellular auxin movement. Positional and functional information about each PIN and PGP is used to construct a dynamic model of auxin transport.

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Flavonoid Accumulation in Arabidopsis Repressed in Lignin Synthesis Affects Auxin Transport and Plant Growth

Sébastien Besseau, Laurent Hoffmann, Pierrette Geoffroy, Catherine Lapierre, Brigitte Pollet, and Michel Legrand

Plant Cell 2007 19: 148-162. First Published on January 19, 2007; 10.1105/tpc.106.044495

The authors show that silencing of the lignin biosynthetic enzyme HCT results in a redirection of the metabolic flux towards flavonoid synthesis and that the reduced size of HCT-silenced plants is due to flavonoid accumulation rather than the alteration in lignin biosynthesis.

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PIP5K9, an Arabidopsis Phosphatidylinositol Monophosphate Kinase, Interacts with a Cytosolic Invertase to Negatively Regulate Sugar-Mediated Root Growth

Ying Lou, Jin-Ying Gou, and Hong-Wei Xue

Plant Cell 2007 19: 163-181. First Published on January 12, 2007; 10.1105/tpc.106.045658

This study explores the physiological function of PIP5K9 through genetic and biochemical analyses. PIP5K9 interacts with cytosolic invertase 1, and genome-wide expression analysis revealed that genes involved in sugar metabolism and multiple developmental processes were altered in pip5k9 and invertase1 mutants, and the altered sugar metabolism in these mutants was confirmed by metabolite profiling.

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A Novel Transcriptional Cascade Regulating Expression of Heat Stress Proteins during Seed Development of Arabidopsis

Sachin Kotak, Elizabeth Vierling, Helmut Bäumlein, and Pascal von Koskull-Döring

Plant Cell 2007 19: 182-195. First Published on January 12, 2007; 10.1105/tpc.106.048165

Arabidopsis HsfA9 encodes a heat stress transcription factor (Hsf) and is expressed exclusively in the late stages of seed development. This study shows that the expression of HsfA9 is regulated by the seed-specific transcription factor ABI3, and HsfA9 in turn functions as a specialized Hsf that influences the developmental expression of heat stress proteins in seeds.

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empty pericarp4 Encodes a Mitochondrion-Targeted Pentatricopeptide Repeat Protein Necessary for Seed Development and Plant Growth in Maize

José F. Gutiérrez-Marcos, Mauro Dal Prà, Anna Giulini, Liliana M. Costa, Giuseppe Gavazzi, Sylvain Cordelier, Olivier Sellam, Christophe Tatout, Wyatt Paul, Pascual Perez, Hugh G. Dickinson, and Gabriella Consonni

Plant Cell 2007 19: 196-210. First Published on January 26, 2007; 10.1105/tpc.105.039594

This work provides insight into the nuclear control of mitochondrial function in plants. It is shown that EMP4, a nuclear-encoded pentatricopeptide protein, regulates the expression of a small group of mitochondrial transcripts in the endosperm.

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Arabidopsis WEE1 Kinase Controls Cell Cycle Arrest in Response to Activation of the DNA Integrity Checkpoint Kristof De Schutter, Jérôme Joubès, Toon Cools, Aurine Verkest, Florence Corellou, Elena Babiychuk, Els Van Der Schueren, Tom Beeckman, Sergeï Kushnir, Dirk Inzé, and Lieven De Veylder Plant Cell 2007 19: 211-225. First Published on January 5, 2007; 10.1105/tpc.106.045047 The cell cycle inhibitory WEE1 gene is identified as a critical target of the DNA replication and DNA damage checkpoints. By arresting the cell cycle, WEE1 couples the onset of mitosis with the completion of DNA repair in cells that suffered DNA damage. [Abstract] [Full Text] [PDF] [Supplemental Data] OPEN ACCESS ARTICLE

The Kinesin ATK5 Functions in Early Spindle Assembly in Arabidopsis

J. Christian Ambrose and Richard Cyr

Plant Cell 2007 19: 226-236. First Published on January 12, 2007; 10.1105/tpc.106.047613

The authors show that plants lacking the kinesin ATK5 exhibit defects in mitotic spindle formation. The localization of ATK5 to early spindle midzones and its ability to coalign microtubules into linear bundles in vitro are consistent with a role in organizing midzone microtubules during spindle formation, thereby fostering spindle organization and integrity.

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

The Arabidopsis irregular xylem8 Mutant Is Deficient in Glucuronoxylan and Homogalacturonan, Which Are Essential for Secondary Cell Wall Integrity

Staffan Persson, Kerry Hosmer Caffall, Glenn Freshour, Matthew T. Hilley, Stefan Bauer, Patricia Poindexter, Michael G. Hahn, Debra Mohnen, and Chris Somerville

Plant Cell 2007 19: 237-255. First Published on January 19, 2007; 10.1105/tpc.106.047720

Mutations in IRX8 cause deficiencies in glucuronoxylan and in a subfraction of homogalacturonan in the secondary cell wall. IRX8 is the third putative glycosyltransferase implicated in xylan synthesis. The data show that IRX8 is required for secondary wall integrity and support the hypothesis that xylan is part of a complex interacting matrix.

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

Chlamydomonas reinhardtii Has Multiple Prolyl 4-Hydroxylases, One of Which Is Essential for Proper Cell Wall Assembly

Katriina Keskiaho, Reija Hieta, Raija Sormunen, and Johanna Myllyharju

Plant Cell 2007 19: 256-269. First Published on January 12, 2007; 10.1105/tpc.106.042739

C. reinhardtii contains 10 genes encoding prolyl 4-hydroxylase-like polypeptides. RNAi suppression of one of them, named Cr-P4H-1, led to inability of the treated cells to regenerate their walls. In addition, the nine other Chlamydomonas P4H-like polypeptides could not fully compensate for lack of Cr-P4H-1 activity and therefore are likely to have different substrate specificities and functions.

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NAC Transcription Factors, NST1 and NST3, Are Key Regulators of the Formation of Secondary Walls in Woody Tissues of Arabidopsis Nobutaka Mitsuda, Akira Iwase, Hiroyuki Yamamoto, Masato Yoshida, Motoaki Seki, Kazuo Shinozaki, and Masaru Ohme-Takagi Plant Cell 2007 19: 270-280. First Published on January 19, 2007; 10.1105/tpc.106.047043 This work shows that NAC domain transcription factors NST1 and NST3 function redundantly and are essential in the formation of secondary walls in woody tissues of Arabidopsis. Putative orthologs of NST1 and NST3 present in the poplar genome suggest that they might be key regulators of secondary wall formation in woody plants and could be used as a tool for the genetic engineering of wood and its derivatives. [Abstract] [Full Text] [PDF] [Supplemental Data] OPEN ACCESS ARTICLE

Arabidopsis PLD2 Regulates Vesicle Trafficking and Is Required for Auxin Response

Gang Li and Hong-Wei Xue

Plant Cell 2007 19: 281-295. First Published on January 26, 2007; 10.1105/tpc.106.041426

This study reports the functional characterization of Arabidopsis PLD2, which is expressed in various tissues and is enhanced by auxin. The results show that this gene product is required for normal cycling of PIN2-containing vesicles and positively mediates auxin responses, including root gravitropism and hypocotyl elongation under high temperature.

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Rice SCAMP1 Defines Clathrin-Coated, trans-Golgi–Located Tubular-Vesicular Structures as an Early Endosome in Tobacco BY-2 Cells Sheung Kwan Lam, Ching Lung Siu, Stefan Hillmer, Seonghoe Jang, Gynheung An, David G. Robinson, and Liwen Jiang Plant Cell 2007 19: 296-319. First Published on January 5, 2007; 10.1105/tpc.106.045708 Rice Secretory Carrier Membrane Protein1 (SCAMP1) was used to study endocytosis in tobacco BY-2 cells. SCAMP1-marked early endosomal compartments resemble previously described partially coated reticulum and trans-Golgi network compartments in plant cells. Treatment with the endocytosis inhibitor wortmannin induced redistribution of SCAMPs from the early endosome to the prevacuolar compartment, possibly as a result of fusion between these compartments. [Abstract] [Full Text] [PDF] [Supplemental Data] OPEN ACCESS ARTICLE

Arabidopsis KAM2/GRV2 Is Required for Proper Endosome Formation and Functions in Vacuolar Sorting and Determination of the Embryo Growth Axis Kentaro Tamura, Hideyuki Takahashi, Tadashi Kunieda, Kentaro Fuji, Tomoo Shimada, and Ikuko Hara-Nishimura Plant Cell 2007 19: 320-332. First Published on January 26, 2007; 10.1105/tpc.106.046631 This study identifies the DnaJ-containing protein KAM2/GRV2 as a key component of the endocytotic pathway. The gene is expressed at the early to middle stages of seed maturation, and the protein is peripherally associated with the membrane surface of uncharacterized compartments. Mutant analysis suggested that KAM2/GRV2 functions in protein trafficking to the vacuoles and in determination of the embryo growth axis. [Abstract] [Full Text] [PDF] [Supplemental Data] OPEN ACCESS ARTICLE

The PEROXIN11 Protein Family Controls Peroxisome Proliferation in Arabidopsis

Travis Orth, Sigrun Reumann, Xinchun Zhang, Jilian Fan, Dirk Wenzel, Sheng Quan, and Jianping Hu

Plant Cell 2007 19: 333-350. First Published on January 12, 2007; 10.1105/tpc.106.045831

The authors show that all five Arabidopsis PEX11 proteins target to peroxisomes and are able to promote peroxisome elongation and proliferation. It is further shown that individual family members play partially redundant and distinct roles and that function is conserved between some Arabidopsis PEX11 proteins and the yeast Pex11p protein.

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

The Acyltransferase GPAT5 Is Required for the Synthesis of Suberin in Seed Coat and Root of Arabidopsis Fred Beisson, Yonghua Li, Gustavo Bonaventure, Mike Pollard, and John B. Ohlrogge Plant Cell 2007 19: 351-368. First Published on January 26, 2007; 10.1105/tpc.106.048033 The authors report the characterization of two mutants of GPAT5, encoding a protein with acyltransferase activity. The results provide evidence for a critical role of GPAT5 in suberin polyester biogenesis in seed coats and roots and the importance of lipid polymer structures for normal function of these organs. [Abstract] [Full Text] [PDF] [Supplemental Data] OPEN ACCESS ARTICLE

In Vivo Participation of Red Chlorophyll Catabolite Reductase in Chlorophyll Breakdown

Adriana Pruzinská, Iwona Anders, Sylvain Aubry, Nicole Schenk, Esther Tapernoux-Lüthi, Thomas Müller, Bernhard Kräutler, and Stefan Hörtensteiner

Plant Cell 2007 19: 369-387. First Published on January 19, 2007; 10.1105/tpc.106.044404

Mutants of red chlorophyll catabolite reductase (RCCR), such as acd2-2, are shown to accumulate red chlorophyll catabolites that trigger cell death. Complementation of acd2-2 with RCCRs exhibiting different stereospecificities causes the formation of respective isomeric chlorophyll catabolites during senescence and provides in vivo demonstration of RCCR function in chlorophyll breakdown.

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

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