Leaf temperature (Tl), the temperature at which leaf-air exchanges of carbon and water occur, varies with ambient air temperature (Ta), regulated by microclimate and species' energy balance traits. Ground and satellite thermal measurements of the Tl-Ta relationship are widely used to infer plants' thermoregulation capacity. On the basis of a global synthesis of observations across diverse climates and biomes, we show that reported thermoregulation patterns vary primarily along temperature gradients. Megathermy (dTl/dTa > 1) is particularly prevalent in warm tropical regions and in sun-exposed canopy-top leaves owing to ineffective dissipation of the often excessively accumulated solar radiation, while limited homeothermy (dTl/dTa < 1) and poikilothermy (dTl/dTa = 1) are reported mostly for cold ecosystems or sub-canopy leaves. Under heat-stressed conditions, some warm-adapted species can abate rapid Tl surge through active stomatal control, unless critical temperature thresholds are exceeded, above which Tl might increase non-linearly as a warning sign of damaging stress. This thermal consideration of stomatal regulation is currently missing in mechanistic models as a source of bias in estimated photosynthetic rates. We highlight the pressing need to develop new stomatal theories that tackle a triple-target optimization between carbon gain, water loss and thermal regulation.

The endoplasmic reticulum (ER) mitigates stress typically through unfolded protein response (UPR) and ER-associated degradation (ERAD) pathways, yet post-transcriptional regulation of ER stress remains poorly defined. N6-methyladenosine (m6A) modification, predominantly enriched near stop codons, can govern mRNA fates via P-bodies or stress granules in stress conditions. m6A also occurs within coding sequences (CDS-m6A), but its role remains unappreciated in plants. Here we demonstrate that m6A ablation sensitizes Arabidopsis ER stress despite normal UPR and ERAD activities. Mechanistically, CDS-m6A co-localizes with ribosome stalling sites and directs co-translational RNA decay (CTRD). Under stress, activation of m6A-triggered CTRD accelerates clearance of ER-engaged transcripts, thereby alleviating translational overload. During geminivirus infection, which increases translational demand on ER, m6A-triggered CTRD also targets viral RNAs, restricting their accumulation, translation and disease progression. Thus, CDS-m6A functions as a pivotal regulator of ER-linked RNA surveillance, establishing an organelle-specific mechanism that integrates RNA stability, protein homeostasis and antiviral defence.

Plants are challenged by multiple biotic (for example, pathogens) and abiotic (for example, heavy metals) stressors. Some transition metals can enhance a plant's defence against pathogens, but the mechanism remains unclear. Here we demonstrate that an Arabidopsis head-to-head gene pair of intracellular nucleotide-binding leucine-rich repeat (NLR) receptors, both expressed in the endodermis of roots, antagonistically control transition metal-enhanced immunity. One NLR, STM2, binds transition metal ions, such as Cd2+, Cu2+ and Zn2+, with its LRR domain to enhance its NAD+ hydrolytic activity and immune responses via the EDS1/PAD4/ADR1 module, triggering enhanced resistance to bacterial wilt Ralstonia solanacearum. The other NLR, STM1, suppresses STM2 to protect plants from transition metal-enhanced immunity and growth inhibition in the presence of excess metals. STM1 also dampens resistance to the pathogen. Our study defines an NLR activated by transition metals and reveals a trade-off between susceptibility to pathogens and sensitivity to transition metals that are pervasive in soil.

Understanding gene regulation is fundamental to plant improvement. However, the lack of plant-specific single-cell assay for transposase-accessible chromatin using sequencing (scATAC-seq) frameworks and cross-species databases has limited insights into cell-type-specific cellular regulation. Here we present 'scPlantReg', an integrated framework and database for plant scATAC-seq data. scPlantReg supports end-to-end analyses from raw data processing to biological interpretation and features 'scATACtor', a supervised machine-learning approach that outperforms existing tools for cell-type annotation. We applied scPlantReg to pearl millet to characterize cell-type-specific chromatin accessibility and identify validated activating and repressing accessible chromatin regions (ACRs), revealing WRKY transcription factors as potential regulators of xylem development. Furthermore, we reanalysed scATAC-seq datasets from 8 plant species, spanning 11 tissues and multiple developmental stages, enabling cross-species comparisons. These analyses uncovered conserved regulatory programmes, including AP2/EREBP-associated ACRs linked to cell wall development and cell-type-conserved TFs across grasses. Collectively, scPlantReg provides a general framework and resource for comparative regulatory analysis in plants.

DNA demethylation is essential for maintaining genome-wide DNA methylation balance. Despite the substantial risk to genome stability, the prevailing paradigm posits that the Arabidopsis demethylase ROS1 prevents genome-wide DNA hypermethylation in vivo mainly through its 5-methylcytosine DNA glycosylase/lyase activity. Here we challenge this paradigm by demonstrating that ROS1, through its occupancy, drives extensive passive demethylation independent of its glycosylase/lyase activity and maintains hypomethylation primarily by preventing de novo DNA methylation. This occupancy-based mechanism eliminates the need for genome-wide base excision for active demethylation, thereby minimizing threats to genomic fidelity and stability. Beyond its role in demethylation, ROS1 also functions as a key marker and regulator of chromatin accessibility. This regulation operates in both DNA methylation-dependent and -independent contexts, with ROS1 acting as either a reserve or active protector of accessible chromatin, depending on the functional state of DNA methylation systems. Our findings redefine the diverse roles of ROS1 in DNA methylation regulation and chromatin accessibility, highlighting their intricate interplay.

Cross-kingdom RNA interference is an emerging concept in plant-pathogen interactions. Here we provide evidence that cross-kingdom RNA interference also occurs in a beneficial plant symbiosis called arbuscular mycorrhiza. The arbuscular mycorrhizal fungus Rhizophagus irregularis transfers small RNAs into plant cells, promoting the colonization of host roots. This finding establishes inter-organismal RNA communication as a new regulatory mechanism of this ancient and widespread symbiosis.

Protein phosphatase 5 (PP5) is a conserved serine/threonine phosphatase regulating growth, stress responses, programmed cell death and immunity across eukaryotes. However, the mechanisms underlying its activation remain poorly understood. Here we demonstrate that the disruption of the plant MEKK1-MKK1/2-MPK4 cascade activates LET7, a plant homologue of PP5, triggering nucleotide-binding leucine-rich repeat (NLR) SUMM2-mediated autoimmunity in Arabidopsis. The binding of LET7 to the co-chaperone protein HOP1 disrupts the autoinhibitory interaction between the tetratricopeptide repeat and phosphatase domains of LET7 in releasing its phosphatase activity. Activated LET7 subsequently dephosphorylates CRCK3, a crucial kinase regulating SUMM2 autoimmunity. Furthermore, HOP1 and LET7 stabilize SUMM2 via their tetratricopeptide repeat domains, highlighting the dual role of the HOP1-LET7 module in dephosphorylating CRCK3 and stabilizing SUMM2 in NLR-mediated immunity. Our studies reveal a conserved mechanism of PP5 activation across plants and animals and elucidate a unique dephosphorylation cascade governing NLR activation.