Measurements of functionally significant xylem variables, such as conduit diameter or vulnerability to embolism, are typically taken from twigs. Ideally, these studies would standardize by distance from the twig tip, given that distance from the terminal end of the conductive stream is the variable that best predicts conduit diameter. To aid efforts to understand the causes of variation in twig conduit diameter, we focus here on the role of leaf length. Longer leaves have wider conduits at the petiole base. It stands to reason that twig tip conduit diameter should closely correlate with petiole base conduit diameter, but this expectation has never been tested. Sampling across 32 orders, 62 families, and 88 species, we show that species with longer leaves have significantly wider conduits at the same distance from the twig tip, as well as lower wood density. Our results underscore the importance of considering both distance from the twig tip and leaf size when comparing functional xylem variables. These findings suggest that selection favoring changes in conduit diameter at the stem tip or base would lead to changes in leaf length and that selection favoring changes in leaf length would involve changes in conduit diameter throughout the shoot xylem.

During photosynthesis, CO 2 uptake is counterbalanced by concurrent CO 2-releasing processes, complicating the interpretation of gas exchange measurements. While photorespiration accounts for a significant portion of this CO 2 release, emerging evidence indicates that there are additional metabolic pathways that release CO 2 during photosynthesis. This metabolism– termed day respiration (often Rd) or respiration in the light ( RL)–is now recognized as an independent and significant source of CO 2 emission during photosynthesis. Here we revisit classical models of photosynthesis and incorporate new insights from isotopic labeling and metabolic flux analysis (MFA) to investigate the biochemical basis of RL. We identified the cytosolic glucose-6-phosphate (G6P) shunt through the oxidative pentose phosphate pathway (OPPP) as the predominant contributor to RL. This shunt explains some long-standing anomalies in Calvin-Benson-Bassham (CBB) cycle labeling. Under non-stressed conditions, RL remains stable across varying CO 2 concentrations and light intensities. Under heat stress, RL shifts toward a plastidial source. Together, these findings resolve longstanding questions about carbon flux during photosynthesis and improve our understanding of RL by explaining its metabolic origin, physiological significance in carbon balance during photosynthesis, and regulation under varying environmental conditions.

Serious allergic reactions are increasing globally. Within this context, fatal anaphylaxis from hazelnut allergies is a critical public health concern. Hazelnuts, which are a common ingredient of many foods, contain many proteins that cause severe allergic reactions. Hazelnuts from all of the major commercial growing locations worldwide contained Spirosoma pollinicola sp proteins. This endotoxin-producing bacterium is linked to the allergenicity of hazelnut pollen. We were unable to remove the contamination by S. pollinicola proteins, showing that that this bacterium is a seed endosymbiont. Comparative proteomics revealed significant variations in the allergenic protein composition of nuts that correlated with patient immune responses. Hazelnuts from provenances 17 and 18 exhibited, lower levels of key antigens, particularly Cor a 9 and Cor a 14, highlighting their potential as candidates for genetic modification to mitigate allergenicity. Moreover, Spirosoma protein persistence may influence hazelnut allergenicity and the patient immune response.

Entomopathogenic nematodes (EPNs) are key biological control agents in agriculture, but their direct effects on plant metabolism and resistance to herbivory remain underexplored. By combining transcriptomic, metabolomic, and herbivore assays, this study aimed at providing a holistic description of maize root responses to EPNs and to assess their potential relevance for plant-herbivore interactions. EPNs triggered a dynamic shift in root metabolism, suggesting a reallocation of primary resources towards chemical defences. After 72 hours, pathways related to ethylene signalling and protein folding, and turnover were downregulated, while pathways for protein export were enriched. Amino acid levels, particularly glutamate and aspartate, decreased, while glucose levels were induced. In parallel, enrichments in alpha-linolenic acid metabolism, glycan biosynthesis, and, albeit not significantly, cutin, suberine, and wax biosynthesis pathways suggested enhanced barrier functions and lipid signalling. Secondary metabolite concentrations, such as benzoxazinoids, were increased. Yet, the overall plant response remained of modest magnitude, as illustrated by a low number of differentially expressed genes exceeding 200 reads. Consistently, EPN exposure did not enhance resistance to subsequent herbivory by the root herbivores Diabrotica balteata or Diabrotica virgifera virgifera. However, the plant responses might influence other belowground interactions, such as those involving plant-microbes or plant-parasitic nematodes, calling for further investigations.

The photorespiratory CO 2 compensation point (Γ*) and the rate of CO 2 release in the light (D L) are critical parameters for understanding the carbon dynamics of C 3 plants. These two parameters can be derived from the widely-used Laisk method as the intercept of linear regression lines fitted to net assimilation rates (A net) versus chloroplast CO 2 partial pressures (C c) obtained at different low-irradiance levels. However, photosynthetic theory indicates curvature in the A net-C c relationship which conflicts with the use of linear relationships for analysis. We, therefore, systematically evaluated the limitations of the use of linear relationships across temperatures from 5 to 40 °C and quantified the sensitivity of errors in Γ* and D L estimates to the selected C c range. We found that wide CO 2 ranges, especially when they exclude the actual Γ*, can introduce substantial biases in parameter estimation with linear regressions, particularly at lower temperatures. It can lead to marked underestimates of Γ*, and biologically unrealistic D L. We propose refining the Laisk method by using a photosynthesis model to analyse data. The model better represents the non-linear A net-C c relationship and yields consistent Γ* and D L estimates, regardless of the CO 2 range used.

Duplicated OsATG9 Genes Antagonize Autophagy to Balance Growth and Drought Tolerance in RiceYiming Li1,†, Yuantai Liu1,†, Mengzhao Shi1,†, Xiaoyun Luo1, Yanshu Huang1, Hao Zeng1, Yunfeng Liu2, Yifeng Huang3, Peng Xu4, Yangwen Qian5, Xixian Li1, Jieying Wang1, Qingjun Xie1,*, Qianying Yang1,*1State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangdong Basic Research Center of Excellence for Precise Breeding of Future Crops, Key Laboratory for Enhancing Resource Use Efficiency of Crops in South China, Ministry of Agriculture and Rural Affairs, Guangdong Provincial Key Laboratory of Plant Molecular Breeding, College of Agriculture, South China Agricultural University, Guangzhou 510642, China.2State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Life Sciences and Technology, Guangxi University, Nanning 530004, China.3Institute of Crop and Nuclear Technology Utilization, Zhejiang Academy of Agricultural Science, Hangzhou, 310001, China.4CAS Key Laboratory of Tropical Plant Resources and Sustainable Use, The Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun, Mengla, Yunnan 666303, China.5WIMI Biotechnology Co. Ltd., Changzhou, 213000, China.*Corresponding author: Dr. Qianying Yang (yangqianying@scau.edu.cn) and Dr. Qingjun Xie (qjxie@scau.edu.cn)†These authors contributed equally to this work.Gene duplication drives functional innovation in evolution, enabling organisms to develop new mechanisms to cope with environmental challenges. One such mechanism is autophagy—a conserved intracellular degradation pathway that not only supports normal development but is also strongly induced by abiotic stresses. Indeed, when plants face drought, autophagy is activated to recycle cellular components (Yagyu et al., 2023). Autophagy initiation involves conserved ATG genes (AuTophaGy related genes), with ATG9 facilitating autophagosome formation (Zhuang et al., 2017). While most plants possess a single ATG9 gene, rice experienced a segmental duplication that yielded two paralogs, OsATG9a and OsATG9b, with positive selection (Ka/Ks >1) (Xia et al., 2011). This raises the question of whether these duplicates have evolved distinct functions, particularly in the context of drought-induced autophagy, which remains poorly understood in rice. In our previous study, we observed that OsATG9b plays a role in determining grain size and quality in rice. Mutations of OsATG9b result in smaller grains and increased chalkiness, whereas its overexpression enhances grain size and quality (Liu et al., 2023). Considering OsATG9b is the duplicated gene from OsATG9a and they experienced positive selection, we hypothesized potential divergent functions of these genes during rice development and in response to environmental stressors.Firstly, we constructed the evolution analysis of ATG9s from 21 species, which revealed that OsATG9a and OsATG9b belong to different clusters (Supporting Information S1: Figure 1). The superfamily domain of ATG9 is highly conserved across different species (Supporting Information S1: Figure 2). Using fluorescent‐tagged constructs, we showed that both OsATG9a and OsATG9b localize to the Golgi apparatus and colocalize with each other, as well as with the core autophagy marker OsATG8b (Supporting Information S1: Figure 3-4). Furthermore, OsATG9a share the similar expression pattern with OsATG9b (Supporting Information S1: Figure 5). To assess their functional roles, we then analyzed two newosatg9a single mutants, two osatg9a osatg9b double mutants, and previous published osatg9b line to confirm that, OsATG9a also positively regulates autophagy and affects rice grain development by degrading TGW6 and other agronomic traits (Supporting Information S1: Figure 6-9), mirroring OsATG9b’s roles in rice development (Liu et al., 2023).Given that OsATG9b originated from a duplication of OsATG9a with a Ka/Ks ratio > 1 (Xia et al. , 2011), it is plausible that OsATG9b has evolved distinct functions compared to OsATG9a under abiotic stress. To explore this hypothesis, we subjected WT, osatg9a-1 ,osatg9a-2 , osatg9b , osatg9a osatg9b-1 andosatg9a osatg9b-2 plants to 20% PEG (simulating drought) and soil-drying conditions. Surprisingly, osatg9a-1 andosatg9a-2 exhibited significantly lower survival rates than WT, whereas osatg9b , osatg9a osatg9b-1 and osatg9a osatg9b-2 mutants displayed higher survival rates than WT (Figure 1A, B, D, E, Supporting Information S1: Figure 10). These results suggested that OsATG9a positively regulates drought stress response, while OsATG9b negatively regulated it, potentially epistatic to OsATG9a. We then assessed the stomatal movement, water-loss rates, drought-related physiological parameters, and transcript levels of drought-resistance marker genes in the leaves after 20% PEG treatment (Supporting Information S1: Figure 11-13). Consistent with survival rate,osatg9a mutants were more drought-sensitive, whereasosatg9b and osatg9a osatg9b mutants were more drought-resistant than WT.We further investigate whether the divergent drought‐resistance functions between OsATG9a and OsATG9b are linked to autophagy. Hence, we firstly checked the autophagy function in response to drought stress. Under 20% PEG treatment, the drought marker gene OsERD1 (Early-Responsive to Dehydration stress ) peaked early and then declined by day 7 under 20% PEG (Supporting Information S1: Figure 14A, B). OsATG9a expression similarly rose and then fell, whereasOsATG9b peaked early but remained unchanged after 24 h (Supporting Information S1: Figure 14C, D). NBR1 (Next to BRCA1 gene 1 protein) is a selective autophagy substrate and it also act as cargo receptors for degradation of other substrates, thus NBR1 can be used as the autophagy markers (Marshall & Vierstra, 2018). In WT plants, OsNBR1 protein levels dropped in 24 h under PEG and soared above baseline after 3 days (Supporting Information S1: Figure 14E-H). AllOsATG genes were upregulated at 6 h post-PEG (Supporting Information S1: Figure 15), suggesting an initial induction of autophagy followed by suppression after one day. By employing the same approaches using previously characterized autophagy mutants and overexpression lines (osatg5 , OsATG5-OE , osatg7 , andOsATG8b-OE ) (Gou et al., 2019), we confirmed that autophagy contributes positively to drought tolerance (Supporting Information S1: Figure 16-18).We further assessed NBR1 protein levels and ATG8-PE levels (phosphatidylethanolamine), which is another stringent criterion for assessing autophagic flux (Marshall & Vierstra, 2018) in osatg9 mutants. The NBR1 PEG:CK ratios of osatg9a-1 and osatg9a-2 were higher than in WT (Figure 1G, H), consistent with the observations in osatg5 and osatg7 (Supporting Information S1: Figure 16E-H), indicating a reduction in autophagy activity in osatg9a in response to drought stress. However, the PEG:CK ratios inosatg9b , osatg9a osatg9b-1 and osatg9a osatg9b-2 were significantly lower than in WT (Figure 1K, L, Supporting Information S1: Figure 19), suggesting a much higher induction of autophagy flux in osatg9b and osatg9a osatg9b compared to WT. Using the ATG8 antibody, our immunoblotting analyses revealed that in osatg9 mutants, reduced ATG8-PE/ATG8 ratios under non-stress conditions indicated compromised basal autophagic flux (Figure 1I, J, M, N). Paradoxically, osatg9b mutants exhibited significantly stronger induction of ATG8-PE conjugation after PEG treatment (Figure 1I, J, M, N), demonstrating enhanced autophagic activation.This functional antagonism was further validated through overexpression studies. The survival rate of OsATG9b-OE was significantly lower than WT under PEG treatment (Figure 1C, F), and soil-drying conditions (Supporting Information S1: Figure 20A, B). Under both normal and PEG conditions, the percentages of completely open stomata and partially open stomata in OsATG9b-OE were higher than in WT, opposite to the trend observed in osatg9b (Supporting Information S1: Figure 20C), which led to higher water loss in OsATG9b-OE compared to WT (Supporting Information S1: Figure 20D). Concordantly, OsATG9b overexpression suppressed drought-induced autophagic flux, as evidenced by attenuated NBR1 degradation (Figure 1K, L). The OsATG8-PE: OsATG8 ratio revealed that under normal conditions, the ratio was higher inOsATG9b-OE line compared to WT (Figure 1M, N), indicating increased autophagic flux in the OsATG9b-OE line under normal condition. However, after PEG treatment, the ratio in theOsATG9b-OE line did not significantly differ from that in WT, but was lower than under normal condition (Figure 1M, N), suggesting a suppression of autophagic flux in the OsATG9b-OE line following drought stress. The reciprocal regulation patterns establish that OsATG9a promotes drought resilience through autophagy potentiation like canonical ATG5/7/8b components, while OsATG9b acts as a novel negative regulator by constraining autophagic flux during stress adaptation.Gene duplicates typically undergo three evolutionary trajectories: non-functionalization, neofunctionalization/subfunctionalization (retained for functional innovation) (Lynch and Conery, 2000). Evolutionarily significant duplicates often develop specialized roles, as exemplified by legume CHI1B ’s exclusive nodulation control versus nonfunctional CHI1A (Liu et al., 2024b). Such divergence enables biological systems to expand adaptive capacity while maintaining regulatory equilibrium.Abscisic acid (ABA) is a key phytohormone that regulates plant drought resistance and response (Haverroth et al., 2023; Liu et al., 2024a). Hence, the ABA-mediated drought responses were investigated to determine functional links between OsATG9a/9b and ABA signaling. The expression levels of ABA pathway components, including OsDREB2A (AP2/EREBP transcription factor ), OsLEA3 (late embryogenesis abundant 3 ), OsbZIP23 (bZIP transcription factor ), MYB2 (MYB Domain Protein 2 ) and OsPYL7 (Pyrabactin Resistance-like Abscisic Acid Receptor ) showed PEG-induced upregulation in WT, osatg9a , and osatg9b mutants. Strikingly, osatg9a exhibited attenuated induction of these genes, while osatg9b displayed amplified responses (Figure 1O), demonstrating divergent ABA pathway regulation. In plants, ABA and autophagy form a feedback loop via ATG8‐interacting proteins, transcriptional regulation, and TOR‐mediated phosphorylation to balance stress responses and growth (Gou et al., 2019). OsATG9b may affect the ABA pathway under drought conditions; it is possible that a key factor in this pathway, in turn, regulates autophagic activity or that OsATG9b’s suppression of autophagy leads to the accumulation of undegraded proteins, thereby disrupting the ABA pathway and compromising drought resistance. We further proposed that OsATG9b has evolved as a critical regulator of autophagy that balances growth and drought tolerance in concert with OsATG9a (Figure 1P).

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Since this is a commentary paper, it does not have an abstract.

To cope with changing external conditions, plants undergo dynamic acclimation processes that remodel their photosynthetic machinery, optimizing energy use while minimizing damage to photosystems (PS). Key photoprotective mechanisms include non-photochemical quenching (NPQ), which dissipates excess excitation energy, and alternative electron transport (AET) pathways, which prevent over-reduction of the photosynthetic electron transport chain. This study provides a comprehensive analysis of how various photoprotective mechanisms contribute to long-term acclimation to high and fluctuating light in Physcomitrium patens, a moss that exhibits well-conserved photoprotective responses bridging algae and vascular plants. Our results demonstrate that modulation of photoprotection around PSII and PSI is critical for maintaining photosynthetic efficiency and enable acclimation to variable light conditions. P. patens mutants deficient in NPQ or AET exposed to high or fluctuating light displayed growth defects, reduced photosynthetic efficiency and unbalanced PSI and PSII activity compared to WT plants. These findings indicate that photosynthetic response under varying light conditions depends on the complementary action of multiple protective strategies, rather than a single dominant photoprotective mechanism.

To mitigate the adverse effects of climate change, development of stress-resilient crops has assumed widespread significance. Though, the dehydration-responsive element binding protein (DREB) transcription factors have been demonstrated to be crucial for stress tolerance in model plants, their role in economically important crops largely remain unclear. In the present study, the role of MusaDREB1G in overcoming drought or cold tolerance was investigated in banana, a plant that is vital for global agriculture and food security. Stress profiling revealed transcription of MusaDREB1G to alter in response to with drought, cold, salinity, or ABA exposures, which was corroborated with stress-induced activation of Pro MusaDREB1G-GUS. Pro MusaDREB1G, which harbors various-stress-associated cis-elements, was primarily active in vascular tissues under control growth conditions. Interestingly, in response to drought, salinity, or cold, the Pro MusaDREB1G was also activated in non-vascular tissues. Overexpression of MusaDREB1G led to a dwarf phenotype, but surprisingly these banana lines showed improved drought or cold tolerance. The overexpression line was characterized in detail to obtain mechanistic insights into this phenomenon. Results showed a distinct elevation in abscisic acid (ABA) and jasmonic acid (JA) content, which correlated well with enhanced expression of stress-related genes in transgenic lines. These findings unveil a novel MusaDREB1G-driven common mechanism for cold/drought tolerance and paves the way for engineering stress-resistant banana crops using MusaDREB1G.

The use of physical models to predict patterns of organismal growth has long interested biologists. Models based on hydraulic or biomechanical principles have been invoked to predict the scaling of tree branching networks, but most assume self-similarity throughout the branching networks and do not consider more than a single physics-based constraint. A more recent model, however, predicts that the allometry of terminal tree branches will differ from the bole and more basal branches. In this model, terminal branch allometry will center around values derived from hydraulic considerations, and differ from the expectations of biomechanical models. Here we evaluate the predictions of this model for the growth of the terminal stems of woody plants using data from 52 species sampled across the seed plant phylogeny and spanning over four orders of magnitude in stem size. We find that the slopes describing terminal stem allometry across seed plants are strongly conserved, despite nearly 400 million years of divergent evolution across the examined lineages. Phylogenetic analysis reveals a strong “pull” towards optimal values, largely consistent with the hydraulic model’s predictions. Our results suggest that the ontogeny of terminal stems in seed plants follow similar allometric scaling rules which operate across evolutionary and ecological scales.

Article type: Brief communication

Trees in temperate and boreal latitudes synchronize their growth-dormancy cycles with seasonal environmental variations to ensure their survival over the years. Dormancy control is crucial during winter when plants cease growth and establish buds to protect their apical meristems from cold temperatures. To overcome endormancy, initiate bud break, and restore growth, plants must be exposed to a specific duration of chilling, referred to as the chilling requirement, which is species- and ecotype-dependent. In this work, we study the novel roles of two TEMPRANILLO-like genes ( TEML1 and TEML2) in the annual cycle of poplar. We demonstrated that Populus TEML genes are regulated by photoperiod, cold temperatures and the circadian clock, and they play a role in the control of endodormancy. Notably, their function diverges from the role of its Arabidopsis ortholog AtTEM, which regulates FLOWERING LOCUS T (FT) transcription and the photoperiodic flowering transcription. Transcriptomic analysis of endodormant buds during winter revealed that the activation of TEML1 and TEML2 promotes endodormancy release by modulating the expression of endodormancy regulators and growth-promoting genes.

Plant water use efficiency (WUE) links physiological processes to ecosystem-scale carbon and water cycles, making it a crucial parameter for climate change adaptation modelling. Climate and stratospheric ozone dynamics expose plants to varying intensity of ultraviolet‐B radiation (UV-B), which affects stomatal function and transpiration. This meta-analysis evaluates UV-B effects on WUE using gas exchange and isotopic proxies. While UV-B radiation reduces stomatal conductance and transpiration, it also suppresses photosynthesis, particularly under non-saturating light. As a result, WUE remains unchanged or declines in UV-B exposed plants, depending on the measurement method. Instantaneous gas exchange-based WUE proxies indicate a decrease, whereas isotope-based proxies, integrating long-term fluxes, show no significant UV-B effect. Notably, UV-B suppresses photosynthesis only in studies using supplemental UV radiation, while UV exclusion in field settings has no significant impact on WUE. Some field studies even report improved WUE under ambient UV-B, suggesting potential adaptive benefits. These findings challenge the assumption that UV-B-induced decreases in transpiration enhance WUE. Instead, they highlight a complex interplay between UV radiation, photosynthesis, and stomatal regulation, emphasizing the need to reconsider UV-B’s role in plant water relations under future climate conditions.

The reproductive cycle of plants features a crucial transition between diploid sporophytic and haploid gametophytic generations. In garlic ( Allium sativum L .), a lack of gametophyte fertility poses significant challenges for breeding. This study conducted a comprehensive comparative transcriptomic analysis across three developmental stages of garlic floral buds from three genotypes with varied fertility profiles to unravel the genetic underpinnings of gametophyte development. Through differential expression analysis and weighted gene co-expression network analysis (WGCNA), we identified key pathways and genes influencing gametophyte fertility. Our analysis revealed significant enrichment in pathways related to lipid metabolism, amino acid biosynthesis, nucleic acid metabolism, and ribosome biogenesis, which are pivotal for gametophyte vitality and development. Furthermore, we identified the AsAMS gene as a key regulator of gametophyte fertility, that may orchestrat tapetal development and microspore formation by modulating the expression of genes involved in lipid biosynthesis and transport, thereby playing a crucial role in pollen viability. The first functional validation using virus-induced gene silencing (VIGS) in garlic further substantiated the role of AsAMS, which demonstrated its critical impact on pollen viability and morphological integrity of reproductive structures. Taken together, these findings not only deepen our understanding of the genetic mechanisms underlying gametophyte development in garlic but also shed light on potential genetic interventions to overcome fertility barriers. By delineating the pathways and key regulators such as AsAMS, this study opens new avenues for enhancing reproductive efficiency in garlic.

Xylem conduit morphology is shaped by the dual challenges of minimizing hydraulic resistance and preventing conduit wall collapse during vertical sap transport. While hydraulic theories predict that conduits widen from tip to base to minimize resistance, theory has not addressed how collapse prevention influences vertical variation in conduit morphology. Additionally, scaling relationships in roots remain largely unexplored. Here, we evaluate existing theories for conduit diameter scaling and derive new theory for vertical variation in thickness-to-span ratios. We test these theories using a novel bootstrapping approach to minimize sampling biases and analyze a dataset of nearly seven million observations spanning above- and belowground organs from five conifer species. As predicted, conduits widened with distance from the stem tip, with scaling exponents closely aligning with theoretical predictions. Conduits also widened from fine roots to coarse roots, mirroring aboveground patterns. Thickness-to-span ratios increased from base to tip and consistently exceeded the predicted critical collapse limit. These findings reveal how the physics of sap transport shape xylem morphology to balance hydraulic efficiency and structural stability. By combining novel theory, robust statistical methods, and comprehensive data, this study refines scaling predictions and advances understanding of mechanisms shaping xylem anatomy across plant organs.

Plants have a wide range of adaptive and protective mechanisms to cope with dehydration. Central in these processes are the Late Embryogenesis Abundant (LEA) proteins, whose levels notably increase in response to dehydration during seed development and vegetative tissues. Understanding the function of LEA proteins is essential for gaining insights into plant development and their adaptive responses to environmental stress. This study focuses on group 6 LEA proteins (LEA6) from Arabidopsis thaliana: AtLEA6-2.1, AtLEA6-2.2, and AtLEA6-2.3. Phylogenetic analysis reveals that LEA6 family emerged with seed plants, pointing to a unique role in seed viability. Functional characterization using T-DNA insertion mutants demonstrated that AtLEA6-2.1, but not AtLEA6-2.2, is essential for tolerance to high-osmolarity and salinity during germination and post-germination growth. AtLEA6-2.1 deficiency also altered root architecture under salinity, increasing primary root length while reducing lateral root number and length, suggesting a role in root development not described before for a LEA protein. Furthermore, AtLEA6-2.1 is critical for seed longevity, as mutants lacking this protein showed reduced germination after natural and accelerated aging. These mutants exhibited increased glass-former fragility, indicating that AtLEA6-2.1 deficiency reduces cellular viscosity, which we found correlates with reduced longevity. Our investigation extends to protective protein assays under dehydration, revealing that the acidic nature of this protein family requires specific conditions for its in vitro protective activity. Overall, this study underscores the essential role of AtLEA6-2.1 in the plant response to low-water availability, seed longevity, and glassy state properties, making it a potential target for enhancing plant resilience to environmental challenges.

Phenotypic switching in bacteria is an evolutionary adaptation that enhances fitness under changing environmental conditions. Here, we report phenotypic switching in Enterobacter sp. SA187 during the transition from its free-living state in soil to its endophytic state in plant root colonization. SA187 phenotypic switching is not host-restricted but occurs during colonization of various host plants. Genome re-sequencing of switcher colonies revealed consistent mutations in the rpoS gene compared to the ancestral strain. Loss-of-function mutations in the rpoS gene were both necessary and sufficient to trigger the phenotypic change, leading to widespread alterations in gene regulation that affected motility, biofilm formation, metabolism and growth. Metabolic analysis further revealed that SA187 switchers have enhanced capacity to thrive in media mimicking the acidic, sucrose-rich apoplastic compartment of plants. Phenotypic switching can be induced in media mimicking plant cell conditions but can be partially reverted on standard bacterial growth media. Overall, our study unravels the genetic mechanism and pivotal role of phenotypic switching in the evolutionary adaptation of a bacterial symbiont to different environments.