Table of Contents
IN BRIEF
REVIEW ARTICLES
RESEARCH ARTICLES
- Phylogenomic Analysis Demonstrates a Pattern of Rare and Ancient Horizontal Gene Transfer between Plants and Fungi
This work reports the use of large-scale genome sequence data analysis to study the incidence of plant-fungi horizontal gene transfer. The authors conclude that HGT between fungi and plants is both rare and ancient, but it has occurred and may have provided gene functions advantageous to habitat spread in plant and fungal species.
- Comparative Analysis between Homoeologous Genome Segments of Brassica napus and Its Progenitor Species Reveals Extensive Sequence-Level Divergence
The genome of Brassica napus is considered to comprise those of its progenitor species, B. rapa and B. oleracea. However, the results show that the genome of the B. napus studied, an oilseed rape (canola) variety, differs considerably at the sequence level from those of representative lines of the progenitor species and has most likely been derived from numerous progenitor lines.
- Reactivation of an Inactive Centromere Reveals Epigenetic and Structural Components for Centromere Specification in Maize
This work shows that one of two centromeres in a dicentric chromosome can become inactivated, losing the molecular markers of centromere identity. Moreover, this dormant centromere can become reactivated, indicating the importance of both epigenetic and structural components of centromere specification.
- Arabidopsis DUO POLLEN3 Is a Key Regulator of Male Germline Development and Embryogenesis
Sperm cell development and double fertilization in angiosperms depend on the coordinated control of germ cell division and gamete differentiation involving the MYB transcription factor DUO1. The authors identify DUO3, a regulatory protein that has a distinct but overlapping role with DUO1 in male germ cell division and specification, and show that DUO3 is conserved in land plants and has a wider regulatory role in embryogenesis.
- Partitioning the Apical Domain of the Arabidopsis Embryo Requires the BOBBER1 NudC Domain Protein
The bobber1 mutant, which has an expanded shoot apical meristem domain and lacks a cotyledon domain, is identified, cloned, and characterized, revealing that BOBBER1 plays a key role in establishing normal patterning in the apical domain of Arabidopsis embryos.
- Two Seven-Transmembrane Domain MILDEW RESISTANCE LOCUS O Proteins Cofunction in Arabidopsis Root Thigmomorphogenesis
This work demonstrates that mutants deficient in the plant-specific integral membrane proteins MILDEW RESISTANCE LOCUS O4 (MLO4) or MLO11 exhibit touch-induced root curling on artificial substrates. The formation of aberrant mlo4-conditioned root coils requires intact transport of the phytohormone auxin.
- The Arabidopsis PLEIOTROPIC DRUG RESISTANCE8/ABCG36 ATP Binding Cassette Transporter Modulates Sensitivity to the Auxin Precursor Indole-3-Butyric Acid
This study shows that a plasma membrane–localized ABC transporter modulates responses to the auxin precursor indole-3-butyric acid (IBA), perhaps by mediating IBA efflux from root cells. The phenotypes of mutations in this transporter implicate IBA-derived IAA in lateral root formation, root hair elongation, and cotyledon expansion.
- The Histidine Kinases CYTOKININ-INDEPENDENT1 and ARABIDOPSIS HISTIDINE KINASE2 and 3 Regulate Vascular Tissue Development in Arabidopsis Shoots
This work demonstrates the essential physiological roles of three plant histidine kinases (CYTOKININ-INDEPENDENT1 and ARABIDOPSIS HISTIDINE KINASE2 and 3) in maintenance of procambial cells in the inflorescence stem.
- The Maize Transcription Factor Myb-Related Protein-1 Is a Key Regulator of the Differentiation of Transfer Cells
Plant nutrient exchange surfaces develop on cells specialized for transport of metabolites. These cells frequently develop intricate cell wall ingrowths that greatly increase the cytoplasm membrane surface and are then termed transfer cells. This study shows that the transfer cell-specific transcription factor MRP-1 is part of the regulatory pathway directing transfer cell differentiation.
- A Structural Basis for the pH-Dependent Xanthophyll Cycle in Arabidopsis thaliana
Zeaxanthin is a carotenoid with a prominent role in protecting plants from excess illumination. This work describes structural data on violaxanthin deepoxidase, the enzyme responsible for zeaxanthin synthesis, and shows how a conformational change triggered by the decrease of the lumenal pH in high light conditions is responsible for activating the enzyme and zeaxanthin biosynthesis.
- Aberrant mRNA Transcripts and the Nonsense-Mediated Decay Proteins UPF2 and UPF3 Are Enriched in the Arabidopsis Nucleolus
This work shows the unexpected presence of mRNAs in the plant nucleolus and enhanced levels of aberrantly spliced mRNAs in the nucleolus. The results suggest that the plant nucleolus has a novel function in quality control of mRNAs.
- Arabidopsis tRNA Adenosine Deaminase Arginine Edits the Wobble Nucleotide of Chloroplast tRNAArg(ACG) and Is Essential for Efficient Chloroplast Translation
Arabidopsis tRNA adenosine deaminase arginine (TADA) specifically edits the wobble nucleotide of chloroplast tRNAArg(ACG) by adenine-to-inosine deamination. The plant TADA is unusually large, but its C-terminal domain is sufficient for its activity both in vitro and in vivo. A mutation in TADA impairs chloroplast translation but is viable, suggesting that exceptions to wobble rules, namely two out of three, occur in plastids.
- Posttranslational Elevation of Cell Wall Invertase Activity by Silencing Its Inhibitor in Tomato Delays Leaf Senescence and Increases Seed Weight and Fruit Hexose Level
This research identified a major regulatory protein, INVINH1, which controls sugar allocation in tomato by limiting the activity of invertase, a key enzyme in the sucrose degradation process. Releasing extra invertase activity by suppressing INVINH1 expression increases leaf longevity, seed weight, and fruit sugar level.
- Helical Growth of the Arabidopsis Mutant tortifolia2 Does Not Depend on Cell Division Patterns but Involves Handed Twisting of Isolated Cells
The results presented show that helical growth in tortifolia2 arises independently of cell division. Instead, handed twisting occurs in trichomes and in cell suspensions derived from the mutant. In young trichomes of tortifolia2, cortical microtubules faithfully predict the direction of cell twisting. The tortifolia2 mutation interrupts hydrogen bonds normally formed between α- and β-tubulin.
- Endocytosis and Endosomal Regulation of the S-Receptor Kinase during the Self-Incompatibility Response in Brassica oleracea
This article reports that the S-receptor kinase involved in self-incompatibility has an unusual subcellular distribution; it localizes predominantly to intracellular compartments and only to discrete domains of the plasma membrane. The receptor–ligand interaction, however, takes place at the plasma membrane and is followed by internalization of the complex into sorting endosomes.
- Sieve Element Ca2+ Channels as Relay Stations between Remote Stimuli and Sieve Tube Occlusion in Vicia faba
The Ca2+ resting level and Ca2+ dynamics during passage of electropotential waves triggered by distant damage was examined in sieve elements. This study infers that subcellular localization of Ca2+ stores in combination with concerted action of Ca2+ channels generate Ca2+ hot spots in the sieve element mictoplasm leading to sieve tube occlusion in Vicia faba.
- Identification and Characterization of Maize and Barley Lsi2-Like Silicon Efflux Transporters Reveals a Distinct Silicon Uptake System from That in Rice
Silicon is a beneficial element in many plants, as it confers protective effects against, multiple stresses. This work identifies a Si efflux transporter from maize and barley. Comparison with rice Si transporters reveals that the uptake system for Si differs between rice and maize/barley.
- The High Light Response in Arabidopsis Involves ABA Signaling between Vascular and Bundle Sheath Cells
The plant hormone abscisic acid (ABA) has been shown to play a key role in the physiological adjustment of Arabidopsis leaves to high light exposure. ABA synthesized in leaf veins coordinates with redox and reactive oxygen signals from chloroplasts of different leaf tissues to activate signaling pathways that regulate the expression of genes important in the leaf's response to high light.
- Shoot Na+ Exclusion and Increased Salinity Tolerance Engineered by Cell Type–Specific Alteration of Na+ Transport in Arabidopsis
Elevated soil salinity has a negative impact on plant growth. This study shows that overexpressing a Na+ transporter specifically in the root stele of Arabidopsis increases the retrieval of Na+ from the transpiration stream, which reduces the amount of Na+ accumulating in the shoot and thereby renders the plant more tolerant to salinity.
- Downy Mildew Resistance in Arabidopsis by Mutation of HOMOSERINE KINASE
A novel form of plant immunity is triggered by the amino acid homoserine, which accumulates in Arabidopsis downy mildew resistant1 plants as a result of mutation in the metabolic gene encoding homoserine kinase.
