Table of Contents
IN BRIEF
RESEARCH ARTICLES
- A Genomic Scan for Selection Reveals Candidates for Genes Involved in the Evolution of Cultivated Sunflower (Helianthus annuus)
A genomic scan for genes showing reduced variation and/or increased differentiation results in the identification of candidates for genes involved in the evolution of cultivated sunflower. Interestingly, candidates for selection during both domestication and improvement are shown to be enriched for genes involved in amino acid synthesis and protein catabolism, as has been seen previously in maize.
- Independent Losses of Function in a Polyphenol Oxidase in Rice: Differentiation in Grain Discoloration between Subspecies and the Role of Positive Selection under Domestication
This work identifies a mutation in domesticated rice in which functional loss of an oxidase gene (Phr1) results in the abolition of grain discoloration in some rice cultivars. The loss of function is likely favored by humans even though it could exact a cost in some environments or in the wild.
- Circadian Clock Proteins LHY and CCA1 Regulate SVP Protein Accumulation to Control Flowering in Arabidopsis
The authors show that LHY and CCA1 control flowering time in continuous light in a GIGANTEA-CONSTANS–independent manner. This involves interactions with the clock gene ELF3 and two MADS box proteins, SHORT VEGETATIVE PHASE and FLOWERING LOCUS C, which together act to coordinate the circadian clock and flowering time in Arabidopsis.
- HAB1–SWI3B Interaction Reveals a Link between Abscisic Acid Signaling and Putative SWI/SNF Chromatin-Remodeling Complexes in Arabidopsis
This work provides a link between a key regulator of ABA signaling and a putative component of SWI/SNF chromatin remodeling complexes, which indicates that these complexes are involved in hormonal response to abiotic stress. Additionally, the results uncover a novel positive regulator of ABA signaling and establish a physical link between hormone signaling and chromatin remodeling machinery.
- Arbuscular Mycorrhiza–Specific Signaling in Rice Transcends the Common Symbiosis Signaling Pathway
The arbuscular mycorrhizal (AM) symbiosis facilitates nutrient uptake in many plants. By monitoring the expression of putative rice orthologs of genes known to be involved in the common symbiosis (SYM) pathway of legumes, this study shows that AM signaling in rice involves a complex signaling network consisting of more than one pathway.
- A SNARE Complex Unique to Seed Plants Is Required for Protein Storage Vacuole Biogenesis and Seed Development of Arabidopsis thaliana
Arabidopsis VAMP727 is an R-SNARE, whose homologs are conserved only in seed plants. It is demonstrated here that VAMP727 plays a pivotal role in the vacuolar transport pathway of developing embryos with Q-SNARE partners SYP22 and VTI11, and with SYP51, which is essential for normal seed development.
- Protein Repair l-Isoaspartyl Methyltransferase1 Is Involved in Both Seed Longevity and Germination Vigor in Arabidopsis
This work provides genetic evidence in Arabidopsis that the repair enzyme protein l-isoaspartyl methyltransferase1 (PIMT1) contributes to seed longevity and vigor under stressful conditions by limiting isoAsp-related protein damage in the mature seed and during early stages of seed germination. This PIMT1 repair pathway is important in facilitating successful seedling establishment.
- Maternal Control of Male-Gamete Delivery in Arabidopsis Involves a Putative GPI-Anchored Protein Encoded by the LORELEI Gene
The lorelei Arabidopsis mutant is impaired in sperm cell release during the fertilization process. Identification of the LORELEI gene revealed that it is expressed in synergid cells and encodes a GPI-anchored protein that is localized at the plasma membrane. LORELEI is likely to play a key role in the signaling between the male and female gametophytes during fertilization.
- Arabidopsis Phosphatidylinositol-4-Monophosphate 5-Kinase 4 Regulates Pollen Tube Growth and Polarity by Modulating Membrane Recycling
Phosphoinositide signaling is crucial for germination and growth of pollen tubes. This study shows that an Arabidopsis lipid kinase, phosphatidylinositol-4-monophosphate 5-kinase 4, plays a key role in membrane recycling, cell architecture, and polarity of growing pollen tubes.
- Two Leucine-Rich Repeat Receptor Kinases Mediate Signaling, Linking Cell Wall Biosynthesis and ACC Synthase in Arabidopsis
This study demonstrates a role for two receptor-like kinases in regulating cellulose biosynthesis in Arabidopsis. These FEI kinases define a novel signaling pathway regulating cell wall biosynthesis and cell expansion. This pathway also includes the previously described SOS5 protein and the enzyme ACC synthase, with ACC likely acting as a novel signal.
- Cellulose Binding Protein from the Parasitic Nematode Heterodera schachtii Interacts with Arabidopsis Pectin Methylesterase: Cooperative Cell Wall Modification during Parasitism
This work functionally characterizes a cyst nematode secretory cellulose binding protein (CBP). The authors determined that CBP functions through the interaction with a host plant cell wall–modifying enzyme. This interaction most likely changes the properties of host plant cell walls in a manner conducive to plant parasitism by cyst nematodes.
- Kinesins Are Indispensable for Interdigitation of Phragmoplast Microtubules in the Moss Physcomitrella patens
Cytokinesis in land plants is mediated by the phragmoplast, a structure built primarily from microtubules. Using the moss Physcomitrella patens, the authors identify two microtubule motor proteins that belong to a plant-specific and poorly characterized family of kinesins and function to hold the phragmoplast together along its midplane.
- Arabidopsis bZIP60 Is a Proteolysis-Activated Transcription Factor Involved in the Endoplasmic Reticulum Stress Response
This report provides evidence that the membrane-anchored form of the Arabidopsis transcription factor bZIP60 is activated by proteolytic cleavage in response to ER stress. This allows the N-terminal fragment containing the bZIP domain to translocate into the nucleus, thereby upregulating many ER stress-responsive genes. Further analyses show that this regulation by proteolytic cleavage appears to be unique to plants.
- The Arabidopsis GRAS Protein SCL14 Interacts with Class II TGA Transcription Factors and Is Essential for the Activation of Stress-Inducible Promoters
A protein regulating the induction of genes involved in the detoxification of harmful chemicals was identified. This protein serves as a coactivator of transcription factors that bind to specific sequences within the promoters of the upregulated genes.
- The Transcriptional Activator Pti4 Is Required for the Recruitment of a Repressosome Nucleated by Repressor SEBF at the Potato PR-10a Gene
This work identifies Pti4, a known transcriptional activator, as a required component for the repression of a defense gene. Thus, these data highlight the two-faced life of dual-function transcription factors. In this case, Pti4 is recruited to its target gene through a bridging protein, SEBF, which itself is a transcriptional repressor.
- A Heterocomplex of Iron Superoxide Dismutases Defends Chloroplast Nucleoids against Oxidative Stress and Is Essential for Chloroplast Development in Arabidopsis
Superoxide dismutases protect plants against reactive oxygen species (ROS). This work shows that two iron superoxide dismutases, FSD2 and FSD3, found in the chloroplasts of Arabidopsis plants, form a heterodimeric protein complex with each other that scavenges ROS and maintains early chloroplast development.
- An Inositolphosphorylceramide Synthase Is Involved in Regulation of Plant Programmed Cell Death Associated with Defense in Arabidopsis
How resistance gene–activated hypersensitive response is regulated remains unclear. This work shows that loss of function of a plant inositolphosphorylceramide synthase gene results in upregulation of salicylic acid–dependent defense signaling leading to cell death in Arabidopsis plants expressing the powdery mildew resistance gene RPW8.
