Volume 26, Issue 1, January 2014

This work identifies direct targets of the MADS box transcription factors FUL1 and FUL2, key regulators of tomato fruit ripening, finding that FUL1 and FUL2 act in the transcriptional regulation of many aspects of ripening, including ripening-related ethylene production and lycopene accumulation, cooperatively with or independently of the MADS box ripening regulators RIN and TAGL1.

This work uses tiling microarrays to map S/MARs on Arabidopsis chromosome 4. S/MARs were found to be spaced more closely than in the large plant and animal genomes studied to date and preferentially enriched in poly(dA:dT) tracts, sequences that resist nucleosome formation. Most S/MARs occur near gene transcription start sites, and these genes show an increased probability of expression.

Transcriptome sequencing of diverse maize inbreds provided insights into the nature of the maize pan-genome, including identification of 8681 loci absent in the B73 reference sequence. Genome-wide association studies using single nucleotide polymorphisms and transcript abundance variants in the maize pan-genome identified loci associated with traits important for fitness and adaptation.

This work shows that translational regulation of gene expression in a recently formed allopolyploid is widespread, reduces transcriptional differences between the polyploid and its diploid progenitors, and correlates with the retention of genes from an older polyploidy event. These findings suggest that translational regulation is significant in both early and long-term responses to polyploidy.

The ability to precisely modify DNA in cells offers great opportunities for basic and applied research, yet it remains difficult to achieve for most plant species. This work explores the use of geminiviruses for genome engineering. Properties of geminiviruses, including extrachromosomal replication and pleiotropic activity of virus proteins, enabled highly efficient editing of the tobacco genome.

This work reports that sro1 (for allelic variation of a wheat SRO gene SRO1) showed higher poly(ADP ribose) polymerase activity than SRO1 due to two residue substitutions and that this protein is involved in both seedling vigor and tolerance to abiotic stress by modulating redox homoeostasis and maintaining genome stability.

This work uses genomic sequencing and microscopy to examine the differences in meiotic stability and fertility between synthetic and natural allopolyploids of Arabidopsis thaliana and A. arenosa. The authors find that the natural allopolyploid A. suecica and its parents have very similar genomic architecture and identify a single locus from A. suecica associated with increased meiotic stability.

Immature pollen of many species can be reprogrammed to form haploid embryos in vitro in response to a stress treatment. This work, in Brassica napus and Arabidopsis thaliana, showed that this stress-induced switch in developmental pathways relies on the inhibition of histone deacetylase activity.

The transcriptional coactivator ANGUSTIFOLIA3 (AN3) stimulates cell division during Arabidopsis leaf development. It is shown that AN3 associates with SWI/SNF chromatin remodeling complexes to regulate the expression of important downstream transcription factors and that the module SWI/SNF-AN3 is a major player in the transition from cell division to cell expansion in developing leaves.

This work demonstrates that WRKY57 functions in the crosstalk between jasmonic acid (JA)– and auxin-mediated signaling during JA-induced leaf senescence. The findings provide a mechanistic insight into how JA-induced leaf senescence is antagonized by auxin via WRKY57.

This work examined the function of the GARP family transcription factor KANADI1 (KAN1), finding that KAN1 binds a GNATA(A/T) cis-motif to repress transcription of target genes involved in auxin biosynthesis, auxin transport, and the auxin response. KAN1 affects auxin responses in opposition to the HD-ZIPIII transcription factor REVOLUTA.

The authors reveal a mechanism underlying jasmonate (JA) and ethylene (ET) antagonism: Interaction between the JA-activated transcription factor MYC2 and the ET-stabilized transcription factor EIN3, reciprocally repressing their transcriptional activity, modulates the antagonistic actions of JA and ET in regulating apical hook curvature, wound-responsive gene expression, and defense against insect attack.

This work examines the consequences of inactivation of the auxin receptor AUXIN BINDING PROTEIN1 and identifies alterations in the transcriptome, cell expansion, cell wall remodeling, and xyloglucan structure. It also reveals the importance of modifications of xyloglucan structure in the cell wall for cell expansion.

Reactive oxygen species (ROS) cause DNA damage. In this work, two SIAMESE/SIAMESE-RELATED (SIM/SMR) genes that encode cyclin-dependent kinase inhibitors are described as being part of a signaling pathway that arrests cell proliferation in response to ROS, revealing a novel cell cycle checkpoint-signaling cascade.

This work identified two ABC transporters important for normal pollen coat deposition and, thus, critical for pollen fitness. The transporters are probably involved in the transfer of pollen coat material from maternal tissues to the pollen surface.

This study elucidates a mechanism whereby calcium enhances the actin filament–severing activity of MICROTUBULE-DESTABILIZING PROTEIN25 (MDP25) in the subapical region of pollen tubes, thereby modulating pollen tube growth in Arabidopsis.

Disruption of the host-cell actin cytoskeleton promotes the susceptibility of plants to diverse microbes. However, the signaling cascades and regulatory proteins linking the perception of microbes to cytoskeletal remodeling remain largely uncharacterized. This study implicates a key actin binding protein, ACTIN DEPOLYMERIZING FACTOR4, in plant innate immune signaling.

During nitrogen starvation under mixotrophic conditions, thylakoids undergo extensive remodeling, leading to photosynthesis inactivation and increased chlororespiration. Degradation of specific photosynthetic protein complexes is triggered by the intracellular production of NO that originates from the rerouting of intracellular nitrite.

FtsH is a ubiquitous protease that mediates the degradation of membrane proteins. The chloroplast FtsH is known for its involvement in repairing photosystem II damaged by light. This work reports the characterization of an ftsh mutant in Chlamydomonas and demonstrates the wider role of FtsH in thylakoid membrane protein maintenance under light as well as nutrient stresses.

This work reveals aspects of the properties and function of the phospholipid cardiolipin (CL). In Arabidopsis, CL mediates mitochondrial fission at least in part by stabilizing the higher order protein complexes of dynamin-related protein DRP3, a major organelle division factor. CL also protects plants from stresses that induce programmed cell death.

Dense vesicles (DVs) are known to be key carriers for sorting of storage proteins to protein storage vacuoles (PSVs) in seed plants. This work characterizes the kelch-repeat protein GLUTELIN PRECURSOR ACCUMULATION3, which forms a functional protein complex with the small GTPase Rab5a via its guanine exchange factor, VPS9a, to regulate directional trafficking of DVs to PSVs in rice endosperm.

This work reveals key structure-function relationships in the photoprotective orange carotenoid protein. The N-terminal domain is shown to be the effector of energy dissipation; it binds to the phycobilisome and quenches fluorescence without prior photochemical activation. The C-terminal domain dynamically regulates the photoprotective activity of the N-terminal domain in response to light.

This study employed forward genetic analysis to uncover an important function of a protein phosphatase, RCF2, and its interacting transcription factor, NAC019, in the activation of HSFs and HSPs and thermotolerance.

Elucidating the mechanism of a plant's responses to phosphate deficiency will help to breed plants that can utilize environmental phosphate more efficiently. Here, we show that the level of the phosphate transporter PT2 is regulated by NITROGEN LIMITATION ADAPTATION and PHOSPHATE2 in a phosphate-responsive manner.

This article demonstrates roles for three subunits of the Plant Mediator complex in recruiting Mediator and RNA polymerase II to specific cold-upregulated genes, facilitating their expression and the subsequent gain of freezing tolerance by the plant. Not all Mediator subunits regulate the same genes, with dark-inducible expression using different subunits than cold-inducible expression.

The Arabidopsis thaliana E4 ligase MUSE3 facilitates the polyubiquitination of immune receptor resistance proteins, including SNC1 and RPS2, leading to more efficient degradation of the target substrates. This E4 activity seems to function downstream of the E3 ligase SCF^CPR1.

This work identifies and characterizes a rice disease resistance gene, XA10, which encodes an inducible, intrinsic terminator protein that triggers programmed cell death in plant and animal cells. This cell death involves disruption of the endoplasmic reticulum and cellular Ca²⁺ homeostasis.