Volume 23, Issue 1, January 2011

This work analyzes an ancient duplicated chromosome pair from grasses that has experienced very different evolution from all other such paleo-duplicated chromosome pairs. It finds chromosome structural stratification, enrichment of autoimmune response–related genes, and accelerated DNA rearrangement and gene loss that are reminiscent of the sex chromosomes of other taxa.

This work examines changes at the protein level during evolutionary recruitment of an enzyme from primary to secondary metabolism. It shows that the recruitment of an enzyme from Leu biosynthesis to the glucosinolate pathway likely involved the loss of the regulatory domain and several other amino acid exchanges.

This work reveals the functional divergence of the three CUP-SHAPED COTYLEDON genes during Arabidopsis leaf development. In particular, it shows that the functions and expression patterns of CUC1 and CUC2 diverged since the formation of these genes by the duplication of a common ancestor within the Brassicale lineage.

This work shows that the mutation of two cytokinin oxidase/dehydrogenases causes the formation of more and larger flowers and describes a previously undiscovered function of cytokinin in ovule-forming placenta tissue. Its findings support a central function of cytokinin in regulating reproductive meristems and highlight the relevance of sink strength in determining yield.

How pollen tubes respond to female cues and precisely deliver sperm cells to the ovule is largely unknown. This article shows that two members of a cation transporter family are required in pollen tube navigation and in shifting polar tip growth.

This study shows that Arabidopsis PLA₂-γ and -Δ, which are specifically expressed in pollen, localize to the endoplasmic reticulum and/or Golgi and that the suppression of PLA₂s disrupts the endomembrane and induces pollen collapse. The PLA₂ product, 18-1:LPE, was found to be required for pollen tube germination.

This work describes Pollen Semi-Sterility1, a kinesin-1 like protein that is involved in regulating male meiosis in rice; in pss1 mutants, chromosome segregation is perturbed, causing reduced pollen viability and partial sterility.

This work identifies 10 putative Populus orthologs of Arabidopsis genes that encode structurally different 1,3-β-glucanases and shows that they localize at and around plasmodesmata. These enzymes are differently regulated by daylength, temperature, GA₃, and GA₄, providing a mechanistic explanation of how cell communication is modulated during the dormancy cycling in synchrony with the seasons.

The pea flowering gene GIGAS regulates a mobile flowering signal and is essential for flowering under long days but not for the ability to respond to photoperiod. This study characterizes the FLOWERING LOCUS T (FT) gene family in pea, identifies one gene (FTa1) as GIGAS, and associates another gene (FTb2) with a second mobile signal and a broader role in photoperiod responsiveness.

The authors show how modulating levels of malate, an abundant metabolite of the tomato fruit, substantially impacts many aspects of fruit ripening and development. Altering malate content also affects postharvest characteristics, including softening susceptibility and pathogenic infection.

Tap46 is a regulatory subunit of a group of protein phosphatases and plays an essential role in plant cell growth and survival as a downstream signaling component of the TOR pathway, which regulates cell growth in coordination with nutrient and environmental conditions.

This work examines the localization and functions of two protein disulfide isomerase family oxidoreductases in formation of protein storage bodies in rice endosperm, finding that the two have nonoverlapping localizations, activities, and biological functions.

This work demonstrates that two members of the Arabidopsis Na⁺/H⁺ antiporter family, NHX5 and NHX6, are critical for normal plant growth and response to stress. Experiments show that the two proteins localize to trafficking endosomal vesicles and demonstrate that NHX5 and NHX6 are required for endosomal trafficking to the vacuole.

Mineral elements are often preferentially stored in vacuoles of specific leaf cell types, but the mechanism and physiological role for this phenomenon is poorly understood. We use single-cell analysis to reveal the genetic basis underpinning mesophyll-specific calcium storage in Arabidopsis leaves and a variety of physiological assays to uncover its fundamental importance to plant productivity.

Cell-to-cell trafficking of RNAs plays an important role in coordinating gene expression at the whole-plant level as well as in virus/viroid infection and host defense response. This work identifies a three-dimensional RNA structure motif in a viroid that mediates trafficking between the leaf mesophyll tissues, providing mechanistic insights into trafficking regulation.

This work shows that a geminivirus-encoded silencing suppressor C2 interacts with a plant host cellular component SAMDC1 and attenuates its fast turnover mediated by the 26S proteasome. As a result, it interferes with the host plant's DNA methylation-related gene silencing mechanism and facilitates geminivirus infection.

A flowering repressor, FLC, has been extensively studied for its role in epigenetic regulation. However, the mechanism of FLC transcription is largely unknown. The authors show that the FRI protein complex recruits basal transcription factors, chromatin modification complexes, and eventually RNA polymerase II to transcribe the FLC gene. This helps to explain the flowering of winter annual Arabidopsis.

The authors use a transgenic approach to show that a close adjustment of ATP synthase activity to linear electron flux is essential for fine-tuning the proton motive force. If ATP synthase activity is too low, lumen overacidification restricts linear electron flux and initiates photoprotective mechanisms (nonphotochemical quenching) in low light, diminishing the quantum efficiency of CO₂ fixation.

This study shows that ClpT in chloroplasts is essential for plant viability and that ClpT specifically regulates the assembly of the Clp proteolytic core. Such a regulatory mechanism adds a new dimension to the functional importance of the chloroplast Clp protease, which has been considered exclusively as a constitutive housekeeping enzyme.

This work shows that MCA1, required for the expression of cytochrome f, is degraded by proteolysis upon interaction with unassembled cytochrome f. MCA1 proteolysis appears to be critical for the assembly-dependent regulation of cytochrome f synthesis, known as Control by Epistasy of Synthesis, which tightly couples its expression to that of its assembly partners.

This work shows that the H3K4 trimethylase ATX1 regulates gene expression via mechanisms different from those reported for its yeast or mammalian homologs. It finds that ATX1 affects transcription at the promoters of target genes by a mechanism distinct from its ability to trimethylate lysine 4 of histone H3 within genes.

This work demonstrated that conjugation of glutathione with indole-3-acetonitrile is catalyzed by GSTF6 in Arabidopsis. Comprehensive feeding experiments of MKK9^DD/pad2 and pad2 plants suggested that glutathione-indole-3-acetonitrile and its catabolites are intermediates within the camalexin biosynthetic pathway.

Control of energy homeostasis is crucial for plant survival. This study identifies a network of bZIP transcription factors that regulate primary metabolism in response to energy starvation.

This study examines how histone modification confers salt stress in Arabidopsis. The floral initiator SKB1 is found to mediate the plant's response to salt stress by altering the methylation status of histone H4R3 and of the small nuclear ribonucleoprotein Sm-like4 (LSM4), thereby affecting the expression of stress-responsive genes.

Rice plants encounter a sequence of environmental perturbations in the natural progression of a flash flood: submergence, reoxygenation, and dehydration. The master regulator of submergence tolerance, SUB1A, coordinates acclimation to all three stresses, providing enhanced tolerance to oxidative stress and dehydration, as well as submergence.