Table of Contents
IN BRIEF
LARGE-SCALE BIOLOGY ARTICLES
Genomic Distribution of Maize Facultative Heterochromatin Marked by Trimethylation of H3K27Chromatin modifications contribute to the regulation of gene expression. The genome-wide distribution of a specific chromatin modification, trimethylation of Lys-27 of histone H3, was profiled in five tissues of maize. There is evidence that this chromatin modification plays an important role in regulating tissue-specific expression for a number of maize genes, including many transcription factors and imprinted genes.
The Potential of Text Mining in Data Integration and Network Biology for Plant Research: A Case Study on ArabidopsisManual evaluation of state-of-the art text mining data reveals promising results for its application in plant network biology. Focusing on Arabidopsis thaliana, an integrated network of text mining and experimental data highlights the complementarity of these resources and the necessity for text mining tools to uncover the latest relevant findings from the literature.
RESEARCH ARTICLES
Maize RNA Polymerase IV Defines trans-Generational Epigenetic VariationIn this study, we show that in maize, RNA polymerase IV defines trans-generational phenotypic variation conditioned by specific haplotypes having promoter-proximal transposon fragments. This assigns a non-Mendelian evolutionary function to these highly conserved plant-specific polymerases.
Interlocking Feedback Loops Govern the Dynamic Behavior of the Floral Transition in ArabidopsisThe floral transition is a key decision in the plant life cycle and under complex regulation. Using modeling and experimental approaches, this work determines a core network of hub activities that accounts for many of the properties of the floral switch. This network exhibits switching behavior and suggests the balance of FT and TFL1 is critical for controlling plant architecture.
BRANCHED1 Promotes Axillary Bud Dormancy in Response to Shade in ArabidopsisArabidopsis BRANCHED1 is required for branch suppression in response to shade. Transcriptional profiling of shade-treated wild-type and brc1 axillary buds revealed a group of ABA response genes and a network of cell cycle– and ribosome-related genes whose mRNA levels are dependent on BRC1 function. These genes may play a key role in the growth-to-dormancy transition in buds.
MAP18 Regulates the Direction of Pollen Tube Growth in Arabidopsis by Modulating F-Actin OrganizationMICROTUBULE-ASSOCIATED PROTEIN18 (MAP18) is known to regulate cortical microtubule organization and polar cell growth in vegetative tissues. This work shows that MAP18 is involved in the regulation of pollen tube morphology and directional growth for accurate micropyle targeting and fertilization by influencing actin organization, rather than microtubule assembly.
Empty Pericarp5 Encodes a Pentatricopeptide Repeat Protein That Is Required for Mitochondrial RNA Editing and Seed Development in MaizeThis work identified a PPR-DYW subgroup protein EMP5 that is required for the C-to-U editing of multiple transcripts in maize mitochondria. The editing at the rpl16-458 site is considered particularly critical to the mitochondrial functions and, hence, to seed development. Interestingly, a deletion of the DYW domain does not abolish the editing, but only reduces the editing efficiency.
Expression of 9-cis-EPOXYCAROTENOID DIOXYGENASE4 Is Essential for Thermoinhibition of Lettuce Seed Germination but Not for Seed Development or Stress ToleranceA gene encoding an enzyme involved in abscisic acid biosynthesis is necessary and sufficient to enable high-temperature inhibition of lettuce seed germination. Introgressed and mutant alleles of NCED4 with reduced expression or enzymatic activity will allow breeding of lettuce cultivars with greater temperature tolerance during germination without compromising tolerance to water stress.
A Major Facilitator Superfamily Transporter Plays a Dual Role in Polar Auxin Transport and Drought Stress Tolerance in ArabidopsisTwo plant isoforms, produced by alternative splicing, of a single membrane transporter from the large Major Facilitator Superfamily possess the same transport activity but distinct tissue and subcellular distribution, thereby allowing this transporter to fulfill two very different physiological functions in drought stress tolerance and root hormonal transport.
DELLA Proteins and Their Interacting RING Finger Proteins Repress Gibberellin Responses by Binding to the Promoters of a Subset of Gibberellin-Responsive Genes in ArabidopsisThis work shows that DELLA proteins physically interact with a member of the BOTRYTIS SUSCEPTIBLE1 INTERACTOR (BOI) protein family and bind to GA-regulated gene promoters to repress GA-induced responses like seed germination, juvenile-to-adult phase transition, and flowering.
FLYING SAUCER1 Is a Transmembrane RING E3 Ubiquitin Ligase That Regulates the Degree of Pectin Methylesterification in Arabidopsis Seed MucilagePectic polysaccharides with a low degree of methylesterification form strong gels and facilitate plant cell adhesion, but their biosynthesis and modification are poorly understood. This study identifies an Arabidopsis transmembrane protein that positively regulates the degree of pectin methylesterification in seed mucilage through a mechanism mediated by ubiquitin.
An RNA Virus-Encoded Zinc-Finger Protein Acts as a Plant Transcription Factor and Induces a Regulator of Cell Size and Proliferation in Two Tobacco SpeciesThis work identifies a mechanism whereby a plant carlavirus subverts the development of its host. It shows that p12 is a virus-encoded transcription factor that is capable of binding and activating promoters of two genes, one of which is involved in activation of leaf cell proliferation.
Allosteric Regulation of Transport Activity by Heterotrimerization of Arabidopsis Ammonium Transporter Complexes in VivoIn plants, AMT-type ammonium transporters are posttranslationally regulated by phosphorylation. This study provides evidence that allosteric regulation is functional in planta and that C-terminal phosphorylation mediates trans-inactivation also in heteromeric AMT complexes containing different AMT isoforms.
Small Interfering RNA–Mediated Translation Repression Alters Ribosome Sensitivity to Inhibition by Cycloheximide in Chlamydomonas reinhardtiiIn the unicellular green alga Chlamydomonas, small RNAs trigger translation repression of target transcripts at a postinitiation step, without or with only minimal mRNA destabilization. The ribosomes associated with small RNA–repressed transcripts display reduced sensitivity to translation inhibition by certain antibiotics such as cycloheximide.
Mapping the Signal Peptide Binding and Oligomer Contact Sites of the Core Subunit of the Pea Twin Arginine Protein TranslocaseThe Tat system uniquely transports fully folded proteins across the thylakoid membrane. Functional domains of the multispanning Tat component cpTatC were dissected with isolated pea chloroplasts onto a three-dimensional model of cpTatC. The results provide insight into folded protein transport and a novel assay for structure-function studies of a membrane protein.
14-3-3 Regulates 1-Aminocyclopropane-1-Carboxylate Synthase Protein Turnover in Arabidopsis14-3-3 proteins function in many cellular processes. Here, we show that 14-3-3s regulate the stability of proteins involved in ethylene biosynthesis. 14-3-3 directly interacts with and regulates the turnover of ACC synthase, a key ethylene biosynthesis enzyme, and the ETO1/EOLs E3 ubiquitin ligases, which regulate ACS protein turnover, thus playing a key role in regulating ethylene biosynthesis.
Regulation of Arabidopsis Leaf Hydraulics Involves Light-Dependent Phosphorylation of Aquaporins in VeinsThe function and regulation of water channel proteins (aquaporins) in plant leaves was dissected by combined genetic, physiological, and proteomic approaches, and their limiting role for water transport in the living cells of veins was established. Phosphorylation of a single aquaporin isoform at two sites was shown to be necessary for enhancement of leaf water permeability in response to darkness.
The Arabidopsis YELLOW STRIPE LIKE4 and 6 Transporters Control Iron Release from the ChloroplastYSL4 and YSL6 are two members of the yellow stripe–like family of metal transporters in Arabidopsis. This study reveals that YSL6 is a protein of the chloroplast envelope, which together with YSL4, is required for the release of iron from the chloroplast. They are active in dedifferentiating chloroplasts of mature embryos and senescent leaves, likely protecting them from free iron toxicity.
Roles of N-Terminal Fatty Acid Acylations in Membrane Compartment Partitioning: Arabidopsis h-Type Thioredoxins as a Case StudyA new understanding of the role of single and double N-terminal fatty acylations in membrane compartment partitioning of plant proteins is achieved using Arabidopsis h-TRXs as a case study.
Modularity of Plant Metabolic Gene Clusters: A Trio of Linked Genes That Are Collectively Required for Acylation of Triterpenes in OatThis study reports on an anthranilate N-methyltransferase, MT1, required for synthesis of antimicrobial triterpenoid defense compounds (avenacins) in oat and, through the characterization of MT1 and the products of other genes within the avenacin metabolic gene cluster, presents a model of the subcellular organization of triterpenoid biosynthesis.
PROTEIN S-ACYL TRANSFERASE10 Is Critical for Development and Salt Tolerance in ArabidopsisS-acylation or palmitoylation, catalyzed by protein S-acyl transferases (PATs), regulates protein targeting and function. This work shows that Arabidopsis PAT10 regulates pleiotropic developmental processes and stress responses. Putative PAT10 substrates include several calcineurin B-like proteins, whose tonoplast association depends on the function of PAT10.
Formation of the Unusual Semivolatile Diterpene Rhizathalene by the Arabidopsis Class I Terpene Synthase TPS08 in the Root Stele Is Involved in Defense against Belowground HerbivoryThis work reports that Arabidopsis roots produce at least four related semivolatile diterpenes named rhizathalenes that have not been previously identified in this or any other plant species. It shows that rhizathalenes act as antifeedants against root-feeding insects.
Phosphorylation of an ERF Transcription Factor by Arabidopsis MPK3/MPK6 Regulates Plant Defense Gene Induction and Fungal ResistancePhosphorylation of Arabidopsis ETHYLENE RESPONSE FACTOR6 (ERF6) by MPK3/MPK6 results in the accumulation of ERF6 protein in vivo, which positively regulates defense gene expression and plant resistance to the necrotrophic fungal pathogen Botrytis cinerea.
BR-SIGNALING KINASE1 Physically Associates with FLAGELLIN SENSING2 and Regulates Plant Innate Immunity in ArabidopsisBR-SIGNALING KINASE1 (BSK1) is a substrate of the brassinosteroid receptor BRI1. This work shows that BSK1 physically associates with FLS2, and a mutation in BSK1 leads to enhanced susceptibility to multiple pathogens as well as defects in the FLS2-mediated reactive oxygen burst, demonstrating that BSK1 plays an important role in plant innate immunity.
Barley MLA Immune Receptors Directly Interfere with Antagonistically Acting Transcription Factors to Initiate Disease Resistance SignalingThe barley immune receptor MLA mediates disease resistance against powdery mildew fungal pathogens. Upon activation, MLA directly interacts with two antagonistically acting transcription factors, MYB6 and WRKY1. MYB6 positively regulates basal and MLA-mediated immune responses, while MYB6 DNA binding is antagonized by direct association with WRKY1 but enhanced by MLA interaction.
RABA Members Act in Distinct Steps of Subcellular Trafficking of the FLAGELLIN SENSING2 ReceptorThis article shows endocytosed FLS2, a flagellin receptor, is initially transported to a hybrid compartment between the trans-Golgi network and multivesicular endosome. It also demonstrates that subgroups of RABA, which is a uniquely expanded RAB group in plants, have distinct roles in the endocytic and exocytic transport of FLS2, indicating functional differentiation among RABA subgroups.
