
Cover image

On the Cover: Cellulose is the major structural component of plant cell walls and has great potential as a renewable source of energy. The plant cellulose synthesis complex (CSC), also called a ‘rosette’ because of its hexameric appearance in transmission electron microscope (TEM) images, is a large multi-subunit transmembrane protein complex responsible for synthesis of cellulose chains and their assembly into microfibrils. Despite the importance of cellulose, fundamental properties of the CSC remain unclear. The number of cellulose synthase (CESA) proteins in the CSC and the number of cellulose chains in a microfibril have been debated for years. Vandavasi et al report a solution structure of the catalytic domain of CESA1 from Arabidopsis thaliana determined by small-angle scattering that provides experimental evidence for the self-assembly of CESA into a stable trimer. This study strongly supports the ‘hexamer of trimers’ model for the rosette CSC that synthesizes an 18-chain cellulose microfibril as its primary product. The cover shows ab initio structures of CESA trimers calculated from small-angle scattering data represented by semi-transparent grey surface envelopes, superposed with the computational atomic models in orange. The trimer models are arranged in a hexameric configuration consistent with the rosette shape observed in TEM images. The view is from the cytosolic side of the membrane. Cellulose microfibrils are visible in the apoplastic space. Cover image credits: Thomas Splettstoesser, scistyle.com, Berlin, Germany.
Volume 170, Issue 1, January 2016
THANK YOU TO REVIEWERS
Thank You to Reviewers and Monitoring Editors
ON THE INSIDE
On the Inside
FOUNDERS REVIEW
The Cytoskeleton and Its Regulation by Calcium and Protons
Calcium and protons exert control over the formation and activity of the cytoskeleton, usually by modulating an associated motor protein or one that affects the structural organization of the polymer.
SCIENTIFIC CORRESPONDENCE
Inhibition of Cell Expansion by Rapid ABP1-Mediated Auxin Effect on Microtubules? A Critical Comment
Critical analysis of a recent article raises questions regarding the inhibition of cell expansion by rapid ABP1-mediated auxin effect on microtubules.
RESEARCH REPORTS
Rj4, a Gene Controlling Nodulation Specificity in Soybeans, Encodes a Thaumatin-Like Protein But Not the One Previously Reported
A thaumatin-like protein regulates gene-for-gene interaction with specific rhizobial strains and controls nodulation specificity in soybeans.
An Optimal Frequency in Ca2+ Oscillations for Stomatal Closure Is an Emergent Property of Ion Transport in Guard Cells
Rapid closure of stomata occurs at an optimum frequency in Ca2+ and voltage oscillations, but this optimum emerges in simulations as a by-product of the transport that drives closure rather than as a signal that regulates it.
BIOCHEMISTRY AND METABOLISM
Regulation of Primary Metabolism in Response to Low Oxygen Availability as Revealed by Carbon and Nitrogen Isotope Redistribution
During low-oxygen stress, activation of Ala and GABA metabolism and bifurcation of the tricarboxylic acid cycle explains the down-regulation of respiratory oxygen consumption.
C4 Photosynthesis in the Rice Paddy: Insights from the Noxious Weed Echinochloa glabrescens
Transcriptomic profiling of the paddy weed Echinochloa glabrescens identifies its C4 molecular signature and genes important for paddy growth.
Redox-Dependent Modulation of Anthocyanin Biosynthesis by the TCP Transcription Factor TCP15 during Exposure to High Light Intensity Conditions in Arabidopsis
The transcription factor TCP15 represses anthocyanin biosynthesis in a redox-dependent manner during high-light intensity conditions.
Enhanced Photosynthesis and Growth in atquac1 Knockout Mutants Are Due to Altered Organic Acid Accumulation and an Increase in Both Stomatal and Mesophyll Conductance
Impaired stomatal closure in a anion channel mutant is accompanied by increased mesophyll conductance, photosynthesis, and leaf area, ultimately enhancing biomass accumulation under controlled conditions.
Reversible Burst of Transcriptional Changes during Induction of Crassulacean Acid Metabolism in Talinum triangulare
Rapid, reversible induction of Crassulacean acid metabolism (CAM) in conjunction with pronounced reconfiguration of carbon metabolism enables Talinum to survive cycles of severe drought.
A Structural Study of CESA1 Catalytic Domain of Arabidopsis Cellulose Synthesis Complex: Evidence for CESA Trimers
Assembly into stable trimers provides strong evidence for 18 protein subunits to assemble in a cellulose synthesis complex that synthesizes an 18-chain cellulose microfibril.
Combining Quantitative Genetics Approaches with Regulatory Network Analysis to Dissect the Complex Metabolism of the Maize Kernel
A metabolic quantitative trait loci study combined with a regulatory network unraveled the genetic architecture of the natural variation of 155 metabolites in mature maize kernels.
Functional Analysis of the Hsp93/ClpC Chaperone at the Chloroplast Envelope
Chloroplast chaperone Hsp93 associates with the inner envelope membrane via interaction with the Tic110 translocon and likely functions in quality control but not in import propulsion of translocating preproteins.
Identification of Arabidopsis GPAT9 (At5g60620) as an Essential Gene Involved in Triacylglycerol Biosynthesis
Arabidopsis GPAT9 is a highly conserved, single-copy, and essential glycerol-3-phosphate acyltransferase involved in seed oil biosynthesis.
The Arabidopsis ABHD11 Mutant Accumulates Polar Lipids in Leaves as a Consequence of Absent Acylhydrolase Activity
Disruption of the ABHD11 hydrolase causes polar lipids accumulation, thereby enhancing plant growth.
The bHLH Transcription Factors TSAR1 and TSAR2 Regulate Triterpene Saponin Biosynthesis in Medicago truncatula
Basic helix-loop-helix family transcription factors from subclade IVa specifically regulate the biosynthesis of the triterpene saponins in a model legume.
CELL BIOLOGY
The Adaptor Complex AP-4 Regulates Vacuolar Protein Sorting at the trans-Golgi Network by Interacting with VACUOLAR SORTING RECEPTOR1
The Arabidopsis AP-4 adaptor complex functions in vacuolar sorting at a subdomain of the TGN by directly recognizing a Tyr-based motif of the receptor.
Profilin-Dependent Nucleation and Assembly of Actin Filaments Controls Cell Elongation in Arabidopsis
Analysis of single actin filament dynamics reveals a novel role for profilin and formins in the generation of branched filament networks in living epidermal cells.
Xyloglucan Deficiency Disrupts Microtubule Stability and Cellulose Biosynthesis in Arabidopsis, Altering Cell Growth and Morphogenesis
A mutant lacking xyloglucan in its cell walls has bundled, aligned cellulose and unstable microtubules that uncover new links between cell wall and cytoskeletal integrity.
Roles of Arabidopsis PARC6 in Coordination of the Chloroplast Division Complex and Negative Regulation of FtsZ Assembly
A plant-specific chloroplast division protein has multiple functions in coordinating and influencing the assembly of internal and external contractile rings across the two envelope membranes.
In Vivo Quantification of Peroxisome Tethering to Chloroplasts in Tobacco Epidermal Cells Using Optical Tweezers
Optical tweezers show that peroxisomes are strongly tethered to chloroplasts and more weakly to other structures.
ECOPHYSIOLOGY AND SUSTAINABILITY
Noninvasive Measurement of Vulnerability to Drought-Induced Embolism by X-Ray Microtomography
X-ray computed microtomography provides a high-resolution, noninvasive method to evaluate vulnerability to drought-induced embolism in living, intact plants.
GENES, DEVELOPMENT AND EVOLUTION
AINTEGUMENTA and AINTEGUMENTA-LIKE6/PLETHORA3 Induce LEAFY Expression in Response to Auxin to Promote the Onset of Flower Formation in Arabidopsis
Two parallel pathways confer floral identity on developing lateral primordia downstream of auxin.
RNA Recognition Motif-Containing Protein ORRM4 Broadly Affects Mitochondrial RNA Editing and Impacts Plant Development and Flowering
Growth and development of Arabidopsis is affected by mutation of a member of the RNA recognition motif gene family that is required for RNA editing of more than 40% of the mitochondrial C targets in Arabidopsis.
Targets of the StBEL5 Transcription Factor Include the FT Ortholog StSP6A
Among the targets of a BEL1-like homeodomain transcription factor are genes involved in growth and hormone metabolism as well as two key tuberization signals.
CONSTANS Controls Floral Repression by Up-Regulating VERNALIZATION2 (VRN-H2) in Barley
The functional characterization of homologs of a flowering-time transcription factor provides new insights into the control of floral repression before vernalization in barley.
Novel Vein Patterns in Arabidopsis Induced by Small Molecules
Numerous compounds inducing leaf vein pattern defects target auxin biology.
The MTL1 Pentatricopeptide Repeat Protein Is Required for Both Translation and Splicing of the Mitochondrial NADH DEHYDROGENASE SUBUNIT7 mRNA in Arabidopsis
A mitochondria-targeted pentatricopeptide repeat protein specifically facilitates the translation of a respiratory chain transcript without inducing any cleavage in its upstream noncoding region.
MEMBRANES, TRANSPORT AND BIOENERGETICS
Revisiting Plant Plasma Membrane Lipids in Tobacco: A Focus on Sphingolipids
Glycosyl-Inositol-Phosphoryl-Ceramides are major lipids of the plasma membrane and form rafts in the outer leaflet, yet extend into the inner leaflet of the membrane through very long-chain fatty acids to interdigitate across the membrane.
The EXS Domain of PHO1 Participates in the Response of Shoots to Phosphate Deficiency via a Root-to-Shoot Signal
A key hydrophobic domain of the PHO1 phosphate exporter plays an important role in the response of shoots to phosphate deficiency.
Constitutive and Companion Cell-Specific Overexpression of AVP1, Encoding a Proton-Pumping Pyrophosphatase, Enhances Biomass Accumulation, Phloem Loading, and Long-Distance Transport
H+-pumping pyrophosphatases appear to function in companion cells to increase phloem loading and long-distance transport, leading to more robust plants with enhanced growth.
SIGNALING AND RESPONSE
Protein S-Acyltransferase 14: A Specific Role for Palmitoylation in Leaf Senescence in Arabidopsis
A protein S-acyltransferase is involved in leaf senescence via modulating salicylic acid metabolism and perception.
The RING Finger Ubiquitin E3 Ligase OsHTAS Enhances Heat Tolerance by Promoting H2O2-Induced Stomatal Closure in Rice
A RING finger ubiquitin ligase functions enhances heat tolerance through the modulation of H2O2-induced stomatal closure.
The Synthetic Elicitor 2-(5-Bromo-2-Hydroxy-Phenyl)-Thiazolidine-4-Carboxylic Acid Links Plant Immunity to Hormesis
Immunity triggered by high doses a and hormetic growth enhancement triggered by low doses of a synthetic elicitor doses are associated with distinct transcriptional profiles.
Phytochrome A and B Function Antagonistically to Regulate Cold Tolerance via Abscisic Acid-Dependent Jasmonate Signaling
Low red/far-red light ratios increase cold tolerance in tomato via the activation of phytochrome A and ABA-dependent JA signaling.
Genetic Variation for Thermotolerance in Lettuce Seed Germination Is Associated with Temperature-Sensitive Regulation of ETHYLENE RESPONSE FACTOR1 (ERF1)
An allele of a gene encoding a transcription factor involved in the ethylene response pathway is associated with the ability of lettuce seeds to germinate at warm temperatures.
Profiling of the Early Nitrogen Stress Response in the Diatom Phaeodactylum tricornutum Reveals a Novel Family of RING-Domain Transcription Factors
A new family of RING-domain transcription factors associated with nitrogen stress is conserved in diatoms.
Arabidopsis PHL2 and PHR1 Act Redundantly as the Key Components of the Central Regulatory System Controlling Transcriptional Responses to Phosphate Starvation
Two transcription factors act redundantly to regulate the transcriptional responses to phosphate starvation at genomic level.
Differential Roles of Two Homologous Cyclin-Dependent Kinase Inhibitor Genes in Regulating Cell Cycle and Innate Immunity in Arabidopsis
Two homologous kinase inhibitor proteins play differential roles in regulating plant cell cycle and defense.
A G-Box-Like Motif Is Necessary for Transcriptional Regulation by Circadian Pseudo-Response Regulators in Arabidopsis
Pseudo-response regulators associate with overlapping sets of putative target genes and require G-box-like cis-regulatory elements for transcriptional activity.
ZINC FINGER OF ARABIDOPSIS THALIANA12 (ZAT12) Interacts with FER-LIKE IRON DEFICIENCY-INDUCED TRANSCRIPTION FACTOR (FIT) Linking Iron Deficiency and Oxidative Stress Responses
Two transcription factors interact and negatively regulate the plant response to prolonged iron deficiency.
Putrescine Alleviates Iron Deficiency via NO-Dependent Reutilization of Root Cell-Wall Fe in Arabidopsis
Putrescine enhances Fe deficiency-induced accumulation of nitric oxide which ultimately leads to the reutilization of cell wall Fe under Fe-deficient conditions.
SYSTEMS AND SYNTHETIC BIOLOGY
A Systems Genetics Approach Identifies Gene Regulatory Networks Associated with Fatty Acid Composition in Brassica rapa Seed
A systems genetics approach identifies gene regulatory networks associated with fatty acid composition in Brassica rapa seed.
Genome-Wide Analysis of Alternative Splicing during Development and Drought Stress in Maize
Alternative splicing is common during development and drought, with a high degree of tissue specificity even among related tissue types.