New Phytologist最新文献

Plants lose water by transpiration through stomatal pores. However, it remains a matter of debate whether relative humidity (RH) in the substomatal cavity may fall below saturation and guard cells experience strong differences water potential driven by RH in the cavity. We developed a gas exchange chamber to control RH and CO₂ at the inner epidermal surface. Vicia faba L. stomata remained open with high stomatal conductance (g_s), even when RH inside was reduced substantially below saturation. Concurrent measurements showed no resolvable decline in bulk cell wall water potential, even with 50 %RH inside, provided the wall space was hydrated. Only when the tissue was allowed to dry did the wall water potential fall below -2 MPa, the stomata close, and g_s collapse to values near zero. These findings concurred with OnGuard model predictions showing large decreases in RH in the leaf under water stress. The observations highlight a steady-state flux from liquid in the cell wall to vapour in the substomatal cavity and across the stomatal pore; they implicate cell wall water in shielding the stomata against leaf airspace humidity; and they pose a challenge to consider the kinetics of evaporative flux behind stomatal transpiration.

Although the cell cycle is conserved between plants and other eukaryotes, there are also significant differences, particularly in G2 regulation. In particular, the WEE1/CELL DIVISION CYCLE25 (CDC25) circuit that establishes G2 timing in animals and fungi is absent in plants. In Arabidopsis thaliana, SIAMESE (SIM), a well-known regulator of endoreplication with homologs throughout land plants, is a cyclin-dependent kinase (CDK) inhibitor that restricts progression through mitosis. Mathematical modeling indicated that SIM may modulate the length of G2 during mitotic cycles in addition to its role in endoreplication. This prediction was tested several ways. First, root growth of sim lagged slightly behind that of wild-type (WT) and the root meristem was longer in sim than in WT. Second, two independent methods of monitoring cell cycle phases, long-term live-cell imaging and 5-ethynyl-2-deoxyuridine (EdU) pulse-chase labeling, showed that G2 is shorter in sim root meristem cortex cells than in WT. Finally, fluorescence levels of a CYCB:GFP fusion that responds directly to G2 CDK activity were consistent with sim mutants having greater G2 CDK activity. These results suggest that, in addition to its role in endoreplication, SIM plays a role in determining the length of G2 during mitotic cycles, potentially substituting in part for the functions of WEE1/CDC25.

In Arabidopsis, stomatal patterning is directed by receptor complexes involving the ERECTA-family (ERf) and SOMATIC EMBRYOGENESIS RECEPTOR KINASE (SERK) proteins. The endosomal sorting complex required for transport (ESCRT) facilitates endocytic degradation of membrane proteins, while its specific role in modulating stomatal patterning remains elusive. Here, we show that the ESCRT-III-associated proteins VPS46.1 and VPS46.2 function redundantly to govern stomatal patterning. Loss of VPS46 function leads to excessive, disorganized stomatal lineage divisions and clustering. Genetic analyses position VPS46 downstream of EPF2 and upstream of the YODA-Mitogen-Activated Protein Kinase (MAPK) cascade. VPS46 proteins localized to late endosomes and colocalized with ERf receptors. The VPS46 mutation specifically disrupted the vacuolar degradation of the ERf-SERKs complex, terminally trapping the receptors on the tonoplast and halting their further cycling. By contrast, the trafficking and function of the brassinosteroid receptor BRI1 were unaffected. Our study identifies VPS46 as a critical regulator that determines the postendocytic fate of the ERf-SERKs receptor complex. It reveals a novel substrate-selective mechanism within the ESCRT pathway, whereby VPS46 ensures the precise spatial patterning of stomata by facilitating degradation of the ERf-SERKs complex to fine-tune signaling output.

Nonphotochemical quenching (NPQ) mechanisms fine-tune light utilisation in the photosynthetic antenna, for example, in response to excess light, to prevent photodamage. NPQ comprises distinct mechanisms, all contributing to photoprotection but acting on different time scales. Preferences for individual mechanisms and NPQ composition are proposed to reflect the organism's lifestyle, especially regarding sessile vs motile styles, with the latter enabling photophobic responses. We analysed photoprotection in the nonmotile, unicellular chlorophycean microalga Botryosphaerella sudetica, belonging to a genus known to form high-light-exposed floating aquatic biofilms. Growth, Chl fluorescence, its nuclear genome, and the expression of photoprotective genes were analysed in comparison with the motile chlorophycean microalga Chlamydomonas reinhardtii. These analyses revealed that B. sudetica is, in contrast to C. reinhardtii, equipped with a constitutive energy-dependent quenching (qE) mechanism based on the constitutive accumulation of protein PSBS, the thylakoid lumen pH-sensor, found throughout the green plant lineage. While qE was the predominant NPQ mechanism in B. sudetica and required zeaxanthin formation, state transitions (qT), which largely contributed to NPQ in C. reinhardtii, played a minor role. These data demonstrate that a core set of NPQ mechanisms conserved in the Viridiplantae is shuffled to meet better the adaptive requirements imposed by the habitat.

Rapid environmental change reshapes both abiotic stress and biotic interactions, yet it remains unclear how these combined forces structure plants' genomic adaptation. In particular, the joint influence of temperature and pollinator identity, two ecological axes undergoing simultaneous global shifts, has rarely been quantified at genomic resolution. We resequenced Brassica rapa L. plants after a six-generation evolution experiment, combining two temperature regimes (ambient vs hot) with three pollination treatments (bumblebee, butterfly, and mixed bumblebee-butterfly), and glasshouse control, to assess how these factors shape genomic responses. Using multiple complementary statistics (allele-frequency trajectories, F_ST outliers, Cochran-Mantel-Haenszel tests, and local score analyses), we found that adaptive genomic responses differed sharply among pollinators and temperatures: warming strengthened selection in community-level pollination, yielding the clearest signals in the hot-generalised treatment; bumblebee pollination showed strong but drift-obscured genomic change; and butterfly treatments exhibited minimal genomic response. Our findings demonstrate that pollinator identity and temperature interact nonadditively to produce distinct, highly context-dependent adaptive trajectories. This work highlights the importance of accounting for demographic variation and ecological complexity when predicting evolutionary responses to climate-driven shifts in species interactions.

Generation of competent offspring is vital for the prosperity of flowering plants. The pistil not only functions as a conduit for pollen tubes to grow to the ovary but also provides a selective venue for facilitating the growth of compatible pollen tubes and discouraging invaders and incompatible pollen. This review integrates recent advances in pollen-pistil interactions on dry stigmas of the Brassicaceae in the domains of self-incompatibility (SI) and cross-compatibility. We first outline the initial recognition mechanisms that distinguish self from nonself pollen and then highlight how key stigma responses are differentially regulated during compatible and incompatible responses, including calcium signaling, exocytosis, cytoskeleton dynamics, reactive oxygen species, aquaporin activity, and cell wall permeability. By linking these discrete cellular events to their physiological outcomes, we provide a unified framework for understanding how Brassicaceae stigmas precisely control fertilization. A deeper understanding of these mechanisms also informs new strategies for improving crop breeding in economically important Brassicaceae species, which widely use SI to produce F1 hybrid seeds.

Mycorrhizal symbioses represent one of the most widespread and ecologically significant plant-microbe interactions, shaping plant nutrition, stress resilience, and ecosystem functioning. Beyond their role in nutrient exchange and systemic defense, growing evidence suggests that these symbioses also influence plant plasticity within and across generations through epigenetic regulation. These mechanisms operate throughout the mutualistic interaction, from fungal recognition and root colonization to symbiosis functioning, by regulating gene networks that control signaling, defense suppression, and nutrient exchange. By integrating environmental cues into potentially heritable gene regulatory states, epigenetic regulation fine-tunes within-generation responses and may also contribute to effects across generations, thereby influencing adaptation and resilience. The extent of mycorrhiza-induced epigenetic inheritance likely depends on the host's reproductive strategy and lifespan. Clonal propagation and shorter-lived hosts tend to preserve epigenetic marks, whereas sexual reproduction and longer-lived species show partial resetting. This contrast shapes offspring performance, ecological interactions, and evolutionary trajectories. Here, we synthesize current knowledge on the epigenetic regulation of mycorrhizal symbioses, draw parallels with other plant-microorganism interactions (including plant-pathogens and plant-endophytes), highlight its role in within-generation plasticity and propose a potential role across generations. We outline future research directions to disentangle the stability, ecological relevance, and evolutionary significance of mycorrhiza-mediated epigenetic inheritance.

An extended period of cold exposure enables the process of vernalization in winter cereals and is important for the synchronised timing of the floral transition. The cereal-specific floral repressor VERNALIZATION2 (VRN2) has an integral role in vernalization, yet this locus remains poorly characterised in facultative spring hexaploid wheat, Triticum aestivum. Through the generation of defined germplasm combined with bespoke experimental protocols, which enable a realistic simulation of annual field-based UK growth conditions, we were able to distinguish gene expression and phenotypic differences at the subgenomic level of VRN2 in hexaploid bread wheat. Our research in a facultative wheat suggests that the tandemly duplicated genes comprising the VRN2 locus, ZCCT1 and ZCCT2, have gene expression patterns that respond to multiple environmental factors. These genes also show coregulation, forming a regulatory loop between ZCCT-D1 and ZCCT-D2. The function of these genes beyond the classic vernalization response is explored in a facultative wheat. Here, we identified that VRN-D2 regulates early tiller development, with an accelerated rate of secondary tiller emergence and presence of coleoptile tillers. The findings identify that the VRN2 loci in bread wheat are formed of multiple genes, which have not only overlapping but also unique regulation and function. Selecting these genes individually may offer a route to alter wheat plant architecture without directly impacting vernalization requirement.

Hybridization and polyploidy are major drivers of plant diversification, often accompanied by shifts in gene expression and genome composition. Small RNAs (smRNAs) are thought to influence such genomic changes, particularly through their interactions with transposable elements (TEs). We quantified smRNAs in established sibling allopolyploids Dactylorhiza majalis and D. traunsteineri and their diploid progenitors to assess how independent allopolyploidization events shaped smRNA landscapes. Despite independent origins, the allotetraploids exhibited substantial overlap in smRNA composition, including transgressive accumulation of smRNAs near genes related to transcriptional regulation, cell division, and stress response. Consistently, TE-associated 24 nt smRNAs more closely resembled the paternal and larger genome, while shorter smRNAs typically reflected the maternal and smaller genome. Nevertheless, distinct patterns were also evident: the older D. majalis showed greater accumulation of smRNAs near genes involved in transcriptional and translational regulation, while the younger D. traunsteineri displayed stronger non-additive patterns, suggesting ongoing resolution of post-polyploid meiotic and mitotic instability. Our results reveal both convergence and divergence in smRNA landscapes among independently formed allopolyploids. Our study highlights the central role of smRNAs in resolving genomic conflict, with possible implications for functional divergence and ecological innovation during polyploid evolution.