ABSTRACT Trunk diseases caused by woody plant pathogens, including Valsa mali and Botryosphaeria dothidea , represent a major threat to global apple production; however, the molecular basis of host resistance remains largely elusive. In this study, we employed TMT‐based quantitative proteomic profiling to compare necrotic and uninfected twig tissues of apple following V. mali inoculation, identifying 904 differentially expressed proteins (DEPs). Among these, the MYB transcription factor, MdMYB1R1, exhibited a pronounced induction in response to pathogen infection. Subcellular localization and transactivation assays revealed that MdMYB1R1 localizes to the nucleus and acts as a transcriptional activator. Transient overexpression of MdMYB1R1 in Nicotiana benthamiana potentiated reactive oxygen species (ROS) accumulation and activated MAPK signaling, correlating with enhanced resistance against Sclerotinia sclerotiorum . Stable overexpression of MdMYB1R1 in apple markedly enhanced resistance to both V. mali and B. dothidea , whereas silencing of MdMYB1R1 impaired disease tolerance. Through DNA affinity purification sequencing (DAP‐seq), yeast one‐hybrid (Y1H), electrophoretic mobility shift assay (EMSA), and dual‐luciferase reporter assays, we demonstrated that MdMYB1R1 binds to the promoter region of MdMAPKKK18 and activates its transcription, a gene encoding a mitogen‐activated protein kinase kinase kinase involved in MAPK signaling. Genetic epistasis analysis further revealed that overexpression of MdMAPKKK18 only partially rescued the compromised resistance in MdMYB1R1 ‐RNAi plants. Collectively, our findings identify MdMYB1R1 as a key positive regulator of apple resistance against trunk fungal diseases, acting at least in part by directly activating the MdMAPKKK18‐mediated MAPK cascade and by regulating additional defense pathways, thus providing a promising candidate for breeding disease‐resistant apple cultivars.
Phosphorus (P) is an essential macronutrient for crop growth, and its deficiency significantly limits wheat productivity, thereby underscoring the importance of improving phosphorus use efficiency (PUE) for global food security. Although proton-pyrophosphatase (Type I H+-pyrophosphatase, VP1, H+-PPases) plays critical roles in plant responses to abiotic stresses, the molecular mechanisms underlying its function in wheat (Triticum aestivum L.) under low-phosphorus (LP) stress remain largely unexplored. Elymus dahuricus, a wild forage grass species, exhibits notable resistance to diverse environmental stresses. In the present study, a VP1-like gene from Elymus dahuricus (EdVP1) was introduced into wild-type (WT) wheat cultivar Shimai366 (SHI366). Two-year field trials conducted under LP conditions demonstrated that overexpression of EdVP1 significantly increased spike number per meter, grain yield, phosphorus harvest index (PHI), and phosphorus use efficiency (PUE). Specifically, transgenic lines OE13 and OE28 exhibited average yield increases of 14.25% and 15.65%, respectively, relative to WT plants over two consecutive years, accompanied by improved photosynthetic rates and chlorophyll content during the grain-filling stage. Additionally, P concentrations in the roots of transgenic lines were significantly elevated compared to SHI366. Subsequent assays under phosphorus-deficient conditions confirmed substantial improvements in both biomass accumulation and root system architecture (RSA) in the transgenic lines. Physiological analyses further demonstrated reduced accumulation of reactive oxygen species (ROS) and enhanced activities of antioxidant enzymes in these lines. Collectively, these findings indicate that the VP1 gene from Elymus dahuricus markedly enhances wheat tolerance to P deficiency. To elucidate the underlying mechanisms of VP1-like genes in wheat, the endogenous plasma membrane (PM) H+-PPases gene TaVP1 (TraesCS7D02G507600), which exhibits the closest evolutionary relationship and highest sequence homology with EdVP1 among grass species, was identified and found to be upregulated in EdVP1 transgenic wheat. TaVP1 expression was predominantly localized in roots and was strongly induced by P-deficient and auxin (IAA) treatment. Notably, auxin levels were significantly increased in the roots of transgenic lines, concomitant with upregulated expression of the auxin influx carrier gene TaAUX1 (TraesCS3B02G401000). Both in vivo and in vitro assays demonstrated a direct interaction between TaVP1 and TaAUX1 at the plasma membrane. Furthermore, factors associated with downstream auxin transport and response, along with the key phosphate starvation transcription factor TaPHR1, exhibit an upregulated expression pattern in the transgenic lines. Taken together, these results reveal a novel mechanism by which H+-PPase enhances tolerance to phosphorus deficiency in wheat through crosstalk with auxin signaling pathways.
In nature, plants are subjected to multiple environmental stress factors simultaneously or sequentially. Recent studies revealed that when three or more stress factors impact a plant simultaneously (termed 'multifactorial stress combination'; MFSC), plant survival declines, even if the intensity of each individual stress involved in the MFSC is low. We previously identified RAP2.3 as a key transcription factor (TF) required for Arabidopsis thaliana survival, specifically under a MFSC of salt+excess light+heat stress (i.e., S + EL + HS). Here we report that RAP2.3 regulates the expression of SIGMA3, a nuclear-encoded factor that directs plastid RNA polymerase to specific plastid promoters, as well as MYB51, a key stress response TF involved in glucosinolate metabolism and oxidative stress responses, specifically during a MFSC of S + EL + HS. Like rap2.3 mutants, myb51 and sig3 mutants display significantly low survival rate specifically under the MFSC of S + EL + HS. Based on MYB51 gene regulatory network analysis and characterisation of jasmonic acid (JA) mutants, we further reveal that suppression of JA signalling could play an important role in promoting plant survival under conditions of S + EL + HS. Our findings uncover an additional layer of the response of plants to MFSC, as well as identify potential targets for breeding crops with enhanced tolerance to climate change.
Plant-herbivore interactions are typically antagonistic, but abiotic stress and compressed life cycles can alter both their intensity and net outcome. Herbivory is generally expected to reduce plant fitness, yet how desert ephemerals respond to low-intensity stem boring remains poorly resolved. We characterised the natural association between the desert ephemeral Strigosella scorpioides and its specialist stem-boring weevil Lixus ochraceus in the Gurbantunggut Desert, northwestern China, combining phenotypic monitoring, tissue nutrient and secondary-metabolite analyses, volatile profiling, behavioural assays and germination trials. Infestation intensity was uniformly low, with each host plant harbouring a single larva. Relative to non-host neighbours, host plants were taller, produced more branches and developed greater leaf area, and attained 2.2-fold greater peak biomass and 2.1-fold greater fruit production, consistent with overcompensation. Host plants contained lower concentrations of three glucosinolates and emitted distinct volatile blends, with a lower proportion of benzyl isothiocyanate and a higher proportion of benzaldehyde; in behavioural assays, females responded to both compounds in a concentration-dependent manner. Seeds from host plants germinated at higher rates under simulated spring snowmelt temperature regimes, although this advantage was temperature-dependent. Together, these results suggest that low-intensity stem boring can coincide with enhanced plant performance and fitness in a highly compressed growing season, and point to plant chemical traits as candidate mediators of plant-herbivore interactions in arid ecosystems. These findings challenge the prevailing assumption that herbivory is invariably antagonistic, suggesting that the sign of such interactions may be more labile than commonly recognised where brief resource windows and close phenological synchrony align.
The timing of the vegetative-to-reproductive transition is critical for plant reproductive success. In Arabidopsis, the B-box transcription factor CONSTANS (CO) is a central regulator of flowering that activates FLOWERING LOCUS T (FT). Although the transcriptional regulation and post-translational stability of CO have been extensively characterised, the mechanisms governing its nuclear accumulation remain poorly defined. Here, we identify IMPORTIN beta 4 (IMB4) as a positive regulator of flowering time. Loss of IMB4 delayed flowering and reduced FT expression without affecting CO transcript abundance. IMB4 interacts with the C-terminal CCT domain of CO, promoted its nuclear accumulation, and thereby enables efficient FT activation. IMB4 and CO show coincident diurnal expression peaks at dusk, suggesting temporal coordination of this transport step. Together, these findings identified IMB4 as a regulator of the CO-FT module and support a role for nucleocytoplasmic partitioning in flowering-time regulation.
