Plant, Cell & Environment最新文献

Abscisic acid (ABA) is a key phytohormone that orchestrates adaptive responses in plants exposed to abiotic stress. The ABA signaling cascade is triggered by ABA-mediated binding of PYRABACTIN RESISTANCE1-LIKE (PYL) receptors to clade A Type 2 C protein phosphatases (PP2CAs). In Arabidopsis thaliana, several constitutively active variants of ABA receptors have been described, offering valuable tools for improving plant tolerance to environmental stresses. To identify amino acid residues in the rice ABA receptor OsPYL5 that are involved in ABA-independent interactions, we implemented a random mutagenesis strategy followed by yeast two-hybrid (Y2H) screening. We identified residues L-93 and N-102 as key residues that influence the ABA independent interaction of OsPYL5 with OsPP2CA51. Substituting these residues with T or Y significantly enhanced the activity of an ABA-responsive reporter in rice protoplasts, even in the absence of ABA treatment. We therefore engineered a double-point mutant, OsPYL5^{L93W N102Y}, which demonstrated a strong ABA-independent interaction with OsPP2CA51 in Y2H assays, elevated activation of ABA-responsive reporter in rice protoplasts, and suppression of PP2CA phosphatase activity in vitro in the absence of ABA. Transgenic rice lines overexpressing OsPYL5^{L93W N102Y} showed delayed germination and growth retardation in the absence of ABA treatment. They also exhibited increased sensitivity to ABA during germination and in early seedling growth assays compared to an OsPYL5-overexpressing transgenic rice line (OsPYL5-OX). Moreover, compared to OsPYL5-OX, they showed dramatic upregulation of ABA-responsive genes both without ABA and with low concentrations of ABA. These transgenic lines also showed enhanced tolerance to drought and salt stress compared to both the control cultivar and OsPYL5-OX. Taken together, our findings not only identify key residues of OsPYL5 that enable ABA-independent receptor function, but also highlight the feasibility of engineering ABA receptors to improve abiotic stress tolerance.

Allopolyploid species often contain specific genes dedicated to suppressing meiotic homoeologous pairing. In common wheat, TaZIP4-B2 and TaMSH7-3D fulfil this role. Nevertheless, to what extent the loss-of-function of these genes may lead to meiotic breakdown in wheat itself and hence generate karyotypic heterogeneity remains incompletely understood. Here, we show that CRISPR/Cas9-generated loss-of-function mutation of either or both TaZIP4-B2 and TaMSH7-3D leads to disrupted meiosis, triggering widespread karyotypic instability including both numerical and structural chromosomal variations (NCVs and SCVs). NCVs predominantly occurred in the D subgenome, involving preferential gains of 2A/4B/5D and losses of 6A/5B/2D, while frequencies of SCVs among subgenomes followed the order of subgenomes D > A > B, with 6A/5B/2D showing the most rearrangements. Notably, karyotypic variation in Tazip4-B2/Tamsh7-3D double mutants showed initial rapid accumulation followed by gradual stabilization across generations. Karyotypic heterogeneity caused extensive phenotypic diversity, including several key agronomic traits. Notably, Tazip4-B2/Tamsh7-3D double mutant showed more intercalary insertional translocations than the classical ph1b deletion mutant, suggesting its advantage in alien genetic introgression. Moreover, tolerance to strong salinity emerged in progenies of the mutants due to karyotypic variation. Our findings demonstrate that the loss-of-function mutation of TaZIP4-B2/TaMSH7-3D promotes rapid karyotype variability, phenotypic diversity, and environmental adaptability in wheat itself, suggesting a novel possibility for wheat improvement by karyotypic renovation.

Multigenerational stress exposure induces stress memory in plants, influencing resource allocation, defence mechanisms, and productivity. Weed competition imposes both resource-based (abiotic) and allelopathic (biotic) stress, engaging overlapping hormonal pathways. This study examined the hormonal and transcriptomic mechanisms underlying multigenerational stress memory in wheat subjected to inter-specific competition with kochia and Italian ryegrass and intra-specific competition with other wheat plants. Phytohormone analysis revealed increased salicylic acid levels, promoting systemic acquired resistance, whereas jasmonic acid levels declined, indicating suppressed jasmonate-mediated defence. Abscisic acid responses varied, reflecting shifts in water-use efficiency. Cytokinins and auxins exhibited generation- and treatment-specific trends, suggesting adaptive resource acquisition but potential hormonal imbalances. These hormonal shifts corresponded with phenotypic responses, where adaptive benefits peaked at Generation 3 before transitioning to maladaptive responses in later generations. Transcriptomic analysis identified dynamic changes in differentially expressed genes (DEGs) and key pathways. Wheat-only competition peaked in stress-responsive DEGs in Generation 3, while wheat-kochia and wheat-ryegrass exhibited early generation transcriptional reprogramming and long-term adaptations. Intra-specific wheat competition showed early generation transcriptomic surges but persistent growth repression in the current study. These findings provide mechanistic insights into multigenerational stress memory mechanisms and reveal how phytohormonal crosstalk and transcriptional reprogramming shape wheat responses to competition stress across generations.

The bright blue colouration of Centaurea cyanus (cornflower) is attributed to a supramolecular pigment formed via metal ion chelation with accumulated cyanidin (Cy) and co-pigments, yet the underlying genetic regulatory mechanisms remain incompletely understood. Elucidating this mechanism will facilitate the molecular breeding of cyanidin-based blue flowers, thereby enhancing the ornamental value of flowering plants. Initially, in vitro blue pigment reconstruction experiments identified that Fe³⁺ is the primary metal ion enabling the blue transformation of Cy, and the molar ratio of Cy to Fe³⁺ was found to be critical. Genomic analysis identified 11 VIT/VTL genes and four CcFers genes in cornflower. Expression profiling revealed an inverse expression relationship between CcVIT1a and CcFers across various tissues. Notably, CcVIT1a specifically and highly expressed in blue-coloured ray florets. Subcellular localization and yeast mutant complementation assay showed CcVIT1a in tonoplast, whereas the CcFers reside in plastids. This spatial separation suggests their coordinated role in regulating intracellular iron homeostasis. Virus-induced gene silencing of CcVIT1a caused a colour shift from blue to violet, indicating its critical role in blue colouration of cornflower. Concurrently, the expression of the CcFer1a was significantly upregulated, while the other three CcFers were downregulated, further supporting the idea that CcVIT1a and the CcFers collaboratively regulate intracellular iron homeostasis. Transient overexpression of CcVIT1a in chrysanthemum CB (Cy-determined blue flowers) sample 'Dante purple' induced a colour transition from red-purple to violet, accompanied by the downregulation of both CmVIT and CmFer1. These findings imply a similar synergistic mechanism governing iron homeostasis in chrysanthemum. This study elucidates the cooperative roles of VIT1 and Fer in regulating intracellular iron partitioning. We demonstrate that upregulation of CcVIT1a enhances iron sequestration into the vacuole, thereby promoting the cyanidin-based blue colouration. Collectively, our findings provide novel molecular insights and a potential strategy for breeding blue flowers through the manipulation of cyanidin and iron metabolism.

Leaf shape displays remarkable diversity, with its evolution hypothesized to reflect adaptive ecophysiological functions. Theoretical models propose that variation in leaf shape-particularly through modifications in effective leaf width (w_e)-primarily influences thermoregulation and hydraulic efficiency. However, comprehensive empirical tests of these hypotheses are lacking. Oxytropis diversifolia E. Peter (Fabaceae) has natural variation in leaf shape (1 leaflet, 1-3 leaflets, and 3 leaflets) and exhibits clinal variation, making it an ideal candidate to test those functional relationships. Here, we quantified leaf morphometrics across populations, logged in situ leaf temperature and gas exchange, and examined leaf anatomy associated with water balance. We confirmed that the production of more leaflets did reduce w_e. While leaves with reduced w_e could stay cooler during the day, the extent of leaf-to-air temperature difference was typically small (often within 1°C), suggesting a limited biological impact. Crucially, we identified a key anatomical trade-off in water relations: reduced w_e yielded beneficial lower chlorenchyma-to-midrib ratios and higher vein density, but at the cost of smaller vascular dimensions. This trade-off likely underpins the observed, context-dependent superior gas exchange of the intermediate phenotype. We propose that the functional significance of leaf shape lies in water relations over thermoregulation, with balancing selection on the anatomical trade-off providing a plausible mechanism maintaining the polymorphism.

In plants, iron homeostasis and oxygen metabolism are strictly related, indeed several Fe-requiring enzymes catalyze reactions that also involve O₂ as a reagent, product, entry or end point of the pathway. Oxygen sensing itself relies on the Fe-dependent enzymes Plant cysteine oxidases. However, the impact of iron deficiencies on the response to hypoxic stresses has not been investigated so far. PCOs channel the ERFVII ethylene-responsive factors into a proteasomal N-degron pathway that connects hypoxia-inducible responses to the stabilization of the ERFVII transcription factors, which act as master regulators of plant hypoxic transcription. Here, we investigated the interplay between low oxygen and Fe-deficiency stresses in A. thaliana. PCO activity in vivo was inferred from the expression of hypoxia marker genes and from the activity of a genetically encoded reporter of ERFVII protein stability. Our results highlight that Fe deprivation can elicit hypoxia-like responses depending on its severity. Moreover, evidence from the pentuple erfVII mutant indicate that the ERFVIIs take part to the responses to chronic Fe-deficiency and fine-tune nutrient content to the shoot of submerged plants growing on moderately Fe-deficient substrates. This work expands the known functions of the ERFVII factors and provides new information to understand plant responses to combined environmental stresses.

Boreal forests are experiencing rapid global warming, which may amplify the impact of temperature on their carbon sink function. However, the factors influencing the sensitivity of the carbon balance to temperature in boreal forests are still not well understood, especially over short timescales. Leveraging the FLUXNET dataset, we calculated the sensitivities of carbon fluxes to temperature anomalies (T_s) across boreal forest (24 sites) on the seasonal scale. Here, a positive T_s value indicates that the carbon flux increases with temperature anomaly, while a negative value suggests the opposite. Results showed that T_s of NEP in early spring was positive for evergreen needleleaf forests but negative for deciduous broadleaved forests. Although T_s of gross ecosystem production (GEP) remained positive, it tended to decrease with increasing temperature and vapour pressure deficit in spring and summer. Associated with this decrease were relatively small changes in T_s of ecosystem respiration (R_e), so that T_s of NEP decreased with increasing temperature and vapour pressure deficit in spring and summer. Both T_s of GEP and R_e increased with ecosystem productivity (represented by annual GEP) in spring, with T_s of GEP being more sensitive, indicating that carbon sinks in sites with lower productivity tended to negatively respond to higher temperature. Young-aged and low-nutrient forests tended to respond negatively to increasing temperatures. Ecosystem productivity and seasonality played an essential role in regulating T_s of NEP. Our results suggest that significant declines in ecosystem productivity may exacerbate the negative response of NEP to elevated temperatures, further compromising carbon sequestration in boreal forests. This understanding is vital both for improving the predictive accuracy of carbon-climate models and for formulating targeted strategies to bolster resilience in the most vulnerable boreal ecosystems.

Photosynthetic light-harvesting complexes mediate light absorption and energy dissipation. By modulating the photosystems' absorption cross-section, they affect both photosynthetic activity and non-photochemical quenching (NPQ). These processes are often studied by spectrally integrated chlorophyll fluorescence, masking their associated spectral information. We explore in Aspen and Arabidopsis npq mutants how qE affects the development of NPQ spectra under two contrasting conditions: in the absence and the presence of photoinhibition. We introduce a new parameter, the development of new emitting species (NESD), during time- and spectrally resolved NPQ inductions, and develop a pipeline to resolve PSII energy-partitioning heterogeneity. LHCII, PsbS, and zeaxanthin are required for NESD. Combining gas exchange, P700 oxidation, and spectrally resolved kinetics, we show that under photoinhibitory conditions, NES can develop even without PsbS or zeaxanthin, producing sustained quenching independent of photoinhibition of PSII or PSI. Furthermore, the absence of LHCII and CURVATURE THYLAKOID 1 leads to increased photoinhibition, indicating that long-term photoprotection relies on LHCII and thylakoid plasticity, whereas PsbS and zeaxanthin mainly facilitate LHCII-dependent quenching. Finally, we show the limitations of traditional parameters in discriminating between photoinhibition and photoprotective sustained quenching and propose time-resolved monitoring of CO₂ assimilation and Y(II) for their accurate assessment.