Articles

Cell-type-specific DNA methylation in plants has only been studied for reproductive tissues. Now a study reports cell-type-specific methylomes of the Arabidopsis root meristem, providing insights into the epigenetic diversity between somatic cell types.

Non-photochemical quenching protects the photosynthetic apparatus of plants from damage in high light conditions. High-resolution time-resolved fluorescence measurements now show that the level of this photoprotection is regulated by subtle changes in the number of LHCIIs in a quenched state.

In response to biotic or abiotic stress, plants can regulate cell–cell communication by modulating plasmodesmal permeability. Here the authors show that callose synthases CalS1/8 are involved in this process.

In high light conditions, terrestrial plants dissipate excess energy as heat. However, microalgae such as Chlamydomonas use state transitions, not to dissipate excess light energy, but to efficiently redistribute it between the photosystems.

Signalling events of early phosphate (P_i) stress in plants are not well known. A study combining transcriptome analyses and grafting experiments now reveals tissue-specific transcriptomic responses to early P_i stress, and a major role for the vascular system in this process.

The genetic diversity of wild relatives of domesticated crops can be useful for developing more productive, nutritious and resilient crop varieties. A comparison of the modelled diversity of crop wild relatives with their representation in gene banks suggests that a systematic effort is needed to improve their conservation and availability for use in plant breeding.

The plant growth hormone auxin is involved in hypocotyl elongation in response to shade and high temperatures. The vas3 mutant now shows that local auxin conjugation is as important for controlling hormone homeostasis as biosynthesis and transport.

Photosystem I (PSI) is thought to be protected from photoinhibition by controlling electron flow from photosystem II. This report shows that PSI is sensitive to light stress but, following photodamage, functions in non-photochemical energy quenching.

It is thought that siRNA derived from the transcription of transposable elements (TEs) in pollen nurse cells moves to sperm cells and represses TE activity. A study has now generated solid molecular data supporting this tantalizing but controversial hypothesis.

The sorting of soluble proteins for degradation in the vacuole is of vital importance in plant cells, and relies on the activity of vacuolar sorting receptors (VSRs). Laboratory experiments with tobacco mesophyll protoplasts suggest that VSRs are required for the transport of ligands from the endoplasmic reticulum and Golgi to the trans-Golgi network/early endosome.

The mRNA cap-binding complex (CBC) has now been shown to form multi-protein complexes with the H3K4 and H3K36 methyltransferases. These complexes are functionally interdependent, coupling chromatin modifications and RNA processing during mature mRNA production.

Two rice WRKY45 alleles show enigmatically opposite effects on resistance to Xanthomonas oryzae. A study now finds that an allele-specific transposon-derived small RNA abolishes WRKY45-mediated resistance by repressing the ST1 gene through DNA methylation.

Crosstalk in plant hormone signalling is important for growth and development. The Arabidopsis transcription factor JUB1 is at the core of a gibberellin/brassinosteroid transcriptional network that controls cell elongation and stress tolerance.

Flavodiiron proteins are the main mediator of pseudocyclic electron transport in photosynthetic organisms spanning cyanobacteria to gymnosperms, but are missing in angiosperms. Experiments with Arabidopsis plants expressing moss flavodiiron proteins suggest that flavodiiron-dependent electron transport can help to protect angiosperms under fluctuating light.

In photosynthesis, excess light energy is dissipated as heat by non-photochemical quenching (NPQ). The localization of proteins and their interactions in thylakoid membranes under high and low light conditions suggests that NPQ involves monomerization of the dimeric protein PsbS and interaction of the resulting monomers with components of trimeric light-harvesting complexes of photosystem II.

Control of cell death is crucial for plant life. A comprehensive screen for suppressors of BAK1/SERK4-mediated cell death identified a component of protein glycosylation pathways and ERQC, and its cysteine-rich receptor-like kinase (CRK) targets.

Specific tissues are developed by legumes during symbiosis to host soil bacteria that will fix nitrogen from air. One single t-SNARE gene in Medicago can switch from a housekeeping to a symbiosome-specific function by alternative transcription.

To understand the mechanisms of grain size control, researchers experimentally reveal that the molecular module miR396/GRF4 regulates rice grain size by activating brassinosteroid signalling. Modulating miR396/GRF4 or brassinosteroid responses can thus be used to improve crop yield.

Arsenic contamination of groundwater and soils threatens the health of tens of millions people worldwide. A series of laboratory experiments suggest that in Arabidopsis, inositol transporters are responsible for arsenite loading into the phloem, the key source of arsenic in seeds.

The molecular network controlling seed size remains elusive. Using genetic and functional analyses, researchers found that the transcription factor OsGRF4 (GS2) forms a module with its regulator OsmiR396 and coactivator GIFs to regulate grain size in rice.