Table of Contents
LETTER TO THE EDITOR
PERSPECTIVE
RESEARCH ARTICLES
- Genome-Wide Distribution of Transposed Dissociation Elements in Maize
Inherited transpositions of the endogenous Ds create stable insertion lines, a resource for targeting gene knockouts and examining mechanisms of transposition. Ds preferentially inserts into genes, at target sites within 16-bpair segments of DNA with specific structural properties. These results suggest approaches to predict insertion sites in transposon mutagenesis experiments.
- Megabase Level Sequencing Reveals Contrasted Organization and Evolution Patterns of the Wheat Gene and Transposable Element Spaces
This article describes the molecular analysis of large contiguous sequences produced from the bread wheat genome. It provides novel insights into the number, distribution, and density of genes along chromosome 3B and reveals an unexpectedly high amount of noncollinear genes compared to model grass genomes.
- VERDANDI Is a Direct Target of the MADS Domain Ovule Identity Complex and Affects Embryo Sac Differentiation in Arabidopsis
This work identifies the putative transcription factor gene VDD as a direct target of MADS box proteins that regulate ovule development. It finds that antipodal and synergid cell identity and/or differentiation are affected in vdd mutant female gametophytes, providing insights into the pathways regulated by the ovule identity factors.
- DWA1 and DWA2, Two Arabidopsis DWD Protein Components of CUL4-Based E3 Ligases, Act Together as Negative Regulators in ABA Signal Transduction
This article reports that DWA1 and DWA2 may be the substrate receptors for a CULLIN E3 ligase and that they interact with themselves and each other. Heterodimeric cooperation between DWAs is a previously unknown regulatory mechanism for the action of CULLIN E3 ligases.
- MOTHER OF FT AND TFL1 Regulates Seed Germination through a Negative Feedback Loop Modulating ABA Signaling in Arabidopsis
This work examines the interactions among MOTHER OF FT AND TFL1 (MFT) and the genes of the abscisic acid (ABA) signaling pathways in the initiation of germination, finding that MFT expression is regulated by key ABA- and gibberellin-responsive factors and MFT in turn also regulates ABA signaling, providing a feedback loop.
- Arabidopsis ROOT UVB SENSITIVE2/WEAK AUXIN RESPONSE1 Is Required for Polar Auxin Transport
This study describes a newly isolated altered auxin response mutant. It finds that the mutant exhibits a reduction in polar auxin transport caused by a decrease in the levels of members of the PIN family of auxin efflux proteins.
- Gravitropism of Arabidopsis thaliana Roots Requires the Polarization of PIN2 toward the Root Tip in Meristematic Cortical Cells
Gravitropism of roots depends on a flow of auxin from the root cap to the zone of elongation via the auxin efflux carrier PIN2. While PIN2 in epidermis and lateral root cap is positioned appropriately, PIN2 in the cortex has the opposite polarity. We report that, despite this, PIN2 functions in the root cortex for optimal gravitropism, apparently by limiting the auxin flow.
- RAV-Like1 Maintains Brassinosteroid Homeostasis via the Coordinated Activation of BRI1 and Biosynthetic Genes in Rice
Brassinosteroid (BR) homeostasis is established by the regulatory circuit between receptor BRI1-mediated signaling and BR synthesis. RAVL1 modulates the strength of the circuit by activating expression of both BRI1 and synthetic genes and is necessary for feedback responses to BR levels.
- Arabidopsis RETINOBLASTOMA-RELATED Is Required for Stem Cell Maintenance, Cell Differentiation, and Lateral Organ Production
Plant development depends on the balance of stem cell renewal and differentiation in several stem cell niches that is achieved by yet unknown regulatory mechanisms. Using inducible RNA interference-mediated downregulation, Arabidopsis RETINOBLASTOMA-RELATED protein is shown to regulate the proliferation, maintenance, and differentiation of stem cells and organ production from stem cell niches.
- Phospholipase A2 Is Required for PIN-FORMED Protein Trafficking to the Plasma Membrane in the Arabidopsis Root
Pharmacological and genetic impairments of phospholipase A2 (PLA2) caused anatomical alterations of the trans-Golgi side and defects in trafficking of auxin-transporting PIN proteins to the plasma membrane in Arabidopsis root epidermal cells. The results implicate PLA2-mediated lipid hydrolysis in PIN trafficking.
- The Deubiquitinating Enzyme AMSH3 Is Required for Intracellular Trafficking and Vacuole Biogenesis in Arabidopsis thaliana
This study identifies AMSH3 as a major deubiquitinating enzyme in Arabidopsis that hydrolyzes ubiquitin chains in vitro and in vivo. It finds that AMSH3 is essential for proper vacuole biogenesis, trafficking from the Golgi to the vacuole, and the vacuolar trafficking of endocytosed cargo.
- Protection of Telomeres 1 Is Required for Telomere Integrity in the Moss Physcomitrella patens
In yeast and vertebrates, the essential telomere binding protein POT1 protects chromosome ends, but in Arabidopsis, POT1 proteins have evolved to bind telomerase instead. This study examines the function of POT1 in the moss Physcomitrella patens. The findings show that moss POT1 functions in a manner similar to yeast and vertebrate POT1. Thus, POT1 proteins are evolving very rapidly in plants.
- Crystal Structures of DNA-Whirly Complexes and Their Role in Arabidopsis Organelle Genome Repair
This work examines the repair of DNA double-strand breaks in the mitochondria and plastids of Arabidopsis. The crystal structures of a Whirly protein bound to single-stranded DNA suggest a role for these proteins in DNA damage tolerance in the organelles.
- Myosin XI Is Essential for Tip Growth in Physcomitrella patens
Class XI myosins are unique to plants and known to function in cytoplasmic streaming. This study demonstrates that the two myosin XI genes present in the moss Physcomitrella patens are functionally redundant, localize to the apical region of actively growing protonemal cells, and play a key role in tip growth.
- Class XI Myosins Are Required for Development, Cell Expansion, and F-Actin Organization in Arabidopsis
The molecular motors termed myosins are involved in transport of subcellular particles in diverse organisms from fungi to animals to plants. Here, we show that myosin-dependent transport is critical for the growth of plant cells and entire plants as well as for proper organization of the cell interior.
- The TOR Pathway Modulates the Structure of Cell Walls in Arabidopsis
The target of rapamycin (TOR) pathway, which is known to regulate cell growth in eukaryotes, is shown to affect cell wall structure in plants. ROL5 (REPRESSOR of LRX1) is identified as a possible mitochondrial component of the TOR pathway.
- The Mg-Chelatase H Subunit of Arabidopsis Antagonizes a Group of WRKY Transcription Repressors to Relieve ABA-Responsive Genes of Inhibition
This work identifies a group of WRKY transcription factors that function as negative abscisic acid (ABA) signaling regulators acting as transcription repressors directly downstream of a previously identified ABA receptor ABAR, describing an ABA signaling pathway from primary events to downstream gene expression.
- The Conserved Splicing Factor SUA Controls Alternative Splicing of the Developmental Regulator ABI3 in Arabidopsis
The Arabidopsisgene ABI3 shows developmentally regulated alternative splicing. ABI3-α and ABI3-β splice variants encode full-length and truncated ABI3 proteins, respectively. The conserved splicing factor SUA reduces splicing of a cryptic ABI3 intron, which leads to the accumulation of ABI3-α. Mutations in sua suppress the frameshift mutant abi3-5 by restoring its reading frame.
- The Molecular Basis for Distinct Pathways for Protein Import into Arabidopsis Chloroplasts
This work investigates the structural determinants for receptor and pathway specificity in chloroplast protein targeting. It provides evidence that the A-domains of the Toc159 family of import receptors are major determinants of distinct pathways for protein import into plastids.
- EOBII, a Gene Encoding a Flower-Specific Regulator of Phenylpropanoid Volatiles' Biosynthesis in Petunia
Floral scent and color play major roles in the plant's life cycle. Using petunia as a model system, a MYB-like factor was identified that transcriptionally regulates floral scent but not pigmentation. The multilayered regulation allows efficient control of metabolic flux in the phenylpropanoid pathway.
- An Orange Ripening Mutant Links Plastid NAD(P)H Dehydrogenase Complex Activity to Central and Specialized Metabolism during Tomato Fruit Maturation
In this study, the characterization of OrrDs, a dominant transposon-tagged tomato mutant deficient in the NDH-M subunit, provided evidence that the plastid NAD(P)H dehydrogenase (NDH) complex is essential for the fruit ripening process and related metabolism.
- Arabidopsis Small Ubiquitin-Like Modifier Paralogs Have Distinct Functions in Development and Defense
This report describes the effect that protein modifications by isoforms of the small ubiquitin-like modifier (SUMO) have on plant development and innate immunity. SUM1 and SUM2 were found to be essential for suppressing defense responses in noninfected plants by preventing accumulation of the defense hormone salicylic acid, whereas SUM3 enhances these defense responses in infected plants.
- Internalization of Flax Rust Avirulence Proteins into Flax and Tobacco Cells Can Occur in the Absence of the Pathogen
This work examines translocation of the flax rust effector protein AvrM, showing that it accumulates in the haustorial wall and extracellular matrix and is delivered into the host cytoplasm. Protein fusions expressed in the plant showed that AvrM can be secreted by the plant and subsequently internalized in the absence of pathogen.
- A Pseudomonas syringae ADP-Ribosyltransferase Inhibits Arabidopsis Mitogen-Activated Protein Kinase Kinases
This study demonstrates that the HopF2 effector of Pseudomonas syringae can interact with MAP KINASE KINASE5 to weaken pathogen-associated molecular pattern–triggered immunity in Arabidopsis and identifies key residues required for this interaction.
- A Vacuolar Arsenite Transporter Necessary for Arsenic Tolerance in the Arsenic Hyperaccumulating Fern Pteris vittata Is Missing in Flowering Plants
Gametophytes of the fern Pteris vittata can accumulate and tolerate more than 1% of their dry weight as arsenic. The authors provide evidence that the ACR3 arsenic transporter protein plays an important role in tolerance to high levels of arsenic by transporting arsenic into the vacuole.
- RNA-Seq Analysis of Sulfur-Deprived Chlamydomonas Cells Reveals Aspects of Acclimation Critical for Cell Survival
Sulfur deprivation of the unicellular alga Chlamydomonas reinhardtii triggers massive changes in the levels of transcripts associated with sulfate assimilation, the synthesis and turnover of sulfur-containing metabolites, and the remodeling of the photosynthetic apparatus and cell wall. These responses are critical for survival of the organism under sulfur deprivation conditions.
- Sho1 and Msb2-Related Proteins Regulate Appressorium Development in the Smut Fungus Ustilago maydis
A crucial step for diseases caused by phytopathogenic fungi is the penetration of the plant cuticle. Here, we highlight that two conserved plasma membrane proteins are required for plant surface sensing and regulate the penetration process via MAP kinase signaling.
