Table of Contents
EDITORIAL
IN BRIEF
LETTERS TO THE EDITOR
REVIEW ARTICLES
RESEARCH ARTICLES
- Calmodulin7 Plays an Important Role as Transcriptional Regulator in Arabidopsis Seedling Development
Calmodulin (CaM) plays multiple regulatory roles in eukaryotes. This study examines the transcriptional regulatory role of CAM7 in early seedling development in plants and further explores the concerted function of CAM7 and HY5 in the regulation of photomorphogenic growth and light-regulated gene expression.
- Auxin Regulates Arabidopsis Anther Dehiscence, Pollen Maturation, and Filament Elongation
This work shows that auxin regulates late development processes in stamens, coordinating anther dehiscence and pollen maturation and independently triggering filament elongation. In addition, auxin, which is mainly synthesized in the anthers by YUC proteins before the inception of late processes, is perceived by the TIR1 AFB receptors when late processes begin.
- SCREAM/ICE1 and SCREAM2 Specify Three Cell-State Transitional Steps Leading to Arabidopsis Stomatal Differentiation
Stomata are formed through a series of events: initiation, proliferation, and terminal differentiation. This work identifies the upstream regulator of the cold-induced transcriptome as the core component of stomatal differentiation and suggests a model strikingly similar to cell-type differentiation in animals.
- Mutations in SUPPRESSOR OF VARIEGATION1, a Factor Required for Normal Chloroplast Translation, Suppress var2-Mediated Leaf Variegation in Arabidopsis
The Arabidopsis var2 variegation mutant has green-and white-sectored leaves due to lack of VAR2, a chloroplast FtsH metalloprotease. Variegation can be suppressed in var2 by impaired chloroplast translation caused by lesions in SVR1 and SVR2, nuclear genes that encode a chloroplast pseudouridine synthase and the ClpR1 subunit of the chloroplast Clp protease, respectively.
- The EPIP Peptide of INFLORESCENCE DEFICIENT IN ABSCISSION Is Sufficient to Induce Abscission in Arabidopsis through the Receptor-Like Kinases HAESA and HAESA-LIKE2
Cell separation allows plants to shed entire organs. In Arabidopsis, the IDA gene is required for abscission of floral organs (e.g., petals). A peptide present in IDA and related IDA-LIKE (IDL) proteins is sufficient for IDA function. Genetic evidence suggests that IDA and IDL proteins are ligands that act through membrane-bound receptors to control cell separation events during plant development.
- Arabidopsis 10-Formyl Tetrahydrofolate Deformylases Are Essential for Photorespiration
This work demonstrates the importance of mitochondrial 10-formyl tetrahydrofolate (THF) deformylase and bifunctional 5,10-methylene THF dehydrogenase/5,10-methenyl THF cyclohydrolase in photorespiration. A model showing the involvement of these folate interconversion enzymes in photorespiration is proposed.
- Mutation of the Plastidial α-Glucan Phosphorylase Gene in Rice Affects the Synthesis and Structure of Starch in the Endosperm
This study identifies rice plants with mutations in the plastidial phosphorylase (Pho1) gene. The reduced starch content and altered amylopectin structure found in the endosperm of these mutants suggests that Pho1 is a key player in starch biosynthesis in the endosperm of rice.
- Badh2, Encoding Betaine Aldehyde Dehydrogenase, Inhibits the Biosynthesis of 2-Acetyl-1-Pyrroline, a Major Component in Rice Fragrance
2-acetyl-1-pyrroline (2AP) is a potent flavor component that gives fragrant rice varieties a distinctive flavor. This study shows that a functional Badh2 allele present in nonfragrant rice varieties encodes an enzyme that inhibits 2AP synthesis by exhausting its precursor, whereas null badh2 alleles, found in fragrant rice varieties, result in 2AP accumulation due to a lack of active BADH2 enzyme.
- Sphingolipid Long-Chain Base Hydroxylation Is Important for Growth and Regulation of Sphingolipid Content and Composition in Arabidopsis
Sphingolipids are essential components of endomembranes and regulators of programmed cell death. This work shows that loss of the C-4 hydroxyl group of sphingolipid long-chain bases (LCBs) in Arabidopsis severely reduces plant growth and increases the content of sphingolipids, primarily with C16 fatty acids. Thus, LCB hydroxylation is important in mediating growth and sphingolipid metabolism.
- Dolichol Biosynthesis and Its Effects on the Unfolded Protein Response and Abiotic Stress Resistance in Arabidopsis
This work describes the isolation and biochemical characterization of the leaf wilting1 (lew1) gene that is responsible for the biosynthesis of dolichols in Arabidopsis. Genetic, molecular, and physiological analyses of the glycosylation defective lew1 mutant show that drought stress signaling converges with endoplasmic reticulum (ER) signaling to regulate ER/UPR (unfolded protein response) and osmotic stress responses.
- Arabidopsis PUB22 and PUB23 Are Homologous U-Box E3 Ubiquitin Ligases That Play Combinatory Roles in Response to Drought Stress
Arabidopsis PUB22 and PUB23 encode U-box–containing E3 ubiquitin ligases that are coordinately induced by abiotic stress and interact with a proteasomal subunit. Loss-of-function mutants show increased tolerance to drought stress, while overexpression increases drought sensitivity. This indicates that PUB22 and PUB23 act coordinately to negatively regulate a drought stress signaling pathway.
- XopD SUMO Protease Affects Host Transcription, Promotes Pathogen Growth, and Delays Symptom Development in Xanthomonas-Infected Tomato Leaves
This work shows that the XopD T3S effector promotes pathogen multiplication in a susceptible host and suppresses the development of chlorosis and necrosis in diseased tissue. Biochemical analysis reveals that XopD possesses DNA binding and transcriptional repressor activity, in addition to SUMO protease activity, indicating that all three activities are required for XopD virulence.
- RXLR-Mediated Entry of Phytophthora sojae Effector Avr1b into Soybean Cells Does Not Require Pathogen-Encoded Machinery
In this study, the authors show that N-terminal RXLR and dEER motifs, together with flanking sequences, are necessary and sufficient to translocate oomycete effector proteins into host plant cells across the plasma cell membrane. Translocation occurs with purified proteins, indicating that no other pathogen machinery is required.
- The Cladosporium fulvum Virulence Protein Avr2 Inhibits Host Proteases Required for Basal Defense
The fungus Cladosporium fulvum secretes the effector protein Avr2 during infection of tomato. This work shows that Avr2 interacts with several extracellular Cys proteases in tomato and Arabidopsis. Avr2 expression causes enhanced susceptibility towards several pathogens in both plant species, and, with RNAi-mediated gene silencing in C. fulvum, it is shown that Avr2 is a genuine virulence factor.
- Tomato Protein Kinase 1b Mediates Signaling of Plant Responses to Necrotrophic Fungi and Insect Herbivory
Tomato Protein Kinase 1b (TPK1b) regulates ethylene-mediated defense against pathogens and insect pests. TPK1b RNA interference plants show increased susceptibility to Botrytis infection and insect feeding and are impaired in ethylene responses. These impaired responses correlate with reduced expression of proteinase inhibitor II in response to Botrytis and 1-aminocyclopropane-1-carboxylic acid.
- Induced Plant Defenses in the Natural Environment: Nicotiana attenuata WRKY3 and WRKY6 Coordinate Responses to Herbivory
WRKY transcription factors regulate plant responses to stress. This work describes two WRKY genes from Nicotiana attenuata that regulate jasmonate (JA) accumulation in response to wounding and herbivore-specific elicitors and JA-mediated defenses against herbivores in 3 years of fieldwork with plants silenced in WRKY expression in the plant's native habitat in the Great Basin Desert.
