Journal of Experimental Botany最新文献

Fusarium verticillioides is a widespread pathogen in cereals that reduces crop yields and poses a threat to food safety by producing the secondary metabolites fumonisins. Maize lipoxygenase genes (LOXs) are involved in the biosynthesis of oxylipins that function as signals in regulating defense. Previously, we showed that mutation of LOX4 is associated with susceptibility to Fusarium verticillioides in kernels, seedlings, and ears via alterations in both transcript profiles and LOX enzymatic activity. In this current study, we show that LOX4 overexpression results in enhanced resistance to pathogen infection and fumonisin contamination, substantiating its role in defense. Transcriptomic and lipidomic analyses revealed that LOX4 overexpression up-regulated expression of 9-LOX genes, thereby increasing the production of 9-oxylipin under fungal infection. The increased expression of jasmonic acid-related genes observed in infected plants was enhanced when LOX4 was overexpressed, correlating with wider accumulation of jasmonic acid-related metabolites. Our results indicate that LOX4 is a good target gene for future engineering of cultivars with increased resistance to F. verticillioides.

Cold stress is a major factor limiting the growth, distribution, and yield of tea (Camellia sinensis). Under low temperatures, tea plants accumulate soluble sugars as osmoprotectants, a process facilitated by transporters such as CsSWEET17. However, upstream regulatory mechanisms controlling CsSWEET17 have been unclear until now. Using a yeast one-hybrid screen, Peng et al. (2025) identified CsDREB28, a cold-inducible DREB transcription factor with an EAR repression motif, as a direct repressor of CsSWEET17 and CsSWEET15. CsDREB28 expression rapidly increased under cold stress. Silencing CsDREB28 in tea plants enhanced CsSWEET17 expression in leaves, increased sugar content, and improved freezing tolerance. In contrast, overexpression in Arabidopsis caused cold sensitivity, early senescence, growth inhibition, and reduced seed yield. The study uncovers a regulatory module in which CsDREB28 negatively controls SWEET sugar transporters, which, besides sugar allocation and cold tolerance, also seem to function in plant development. Thereby, it deepens our understanding of sugar transport regulation in response to abiotic stress in plants.

Parasitic plants of the Orobanchaceae family, particularly Striga hermonthica, rank among the world's most devastating agricultural weeds (Jamil et al., 2021). They inflict massive yield losses on staple cereal crops across Africa, including sorghum, millet, and rice, as well as globally on other essential crops such as maize, rapeseed, tomato, and legumes (Parker et al., 2009; Bouwmeester, 2018). These root parasites have evolved a specialized organ called the 'haustorium' that connects to the vascular system of the host to siphon water, minerals, and nutrients (Yang et al., 2015). A critical component of this strategy is maintaining a lower water potential (LWP) than the host to drive a bulk flow of xylem sap into the parasite (Smith and Stewart, 1990; Katagiri et al., 2025).

Post-transcriptional RNA editing and retrograde signaling in chloroplasts are crucial for coordinating gene expression between the chloroplasts and the nucleus in flowering plants, and yet the molecular link between them remains poorly understood. This study reveals that the Arabidopsis isoprenoid biosynthesis enzyme 1-hydroxy-2-methyl-2-(E)-butenyl-4-diphosphate synthase (HDS), a known regulator of retrograde signaling, is also involved in chloroplast RNA editing. We found that the loss of HDS function significantly altered RNA editing efficiency at multiple specific sites in chloroplast transcripts. HDS mutants exhibited a pale phenotype and early seedling lethality, with severely impaired chloroplast development and photosynthetic apparatus assembly. Moreover, we demonstrated that HDS physically interacts with the chloroplast multiple-site RNA-editing factors MORF2 and MORF9 and participates in RNA editing by modulating their dimerization. Taken together, our results indicate that the important retrograde signaling regulator HDS also plays a novel role in chloroplast RNA editing, providing insights into the connection between organelle-to-nucleus communication and RNA metabolism in chloroplasts.

Wheat rapidly induces complex metabolic reactions in response to cold stress, yet the physiological mechanisms governing its natural recovery process remain poorly understood. In a 2 year pot experiment, we examined recovery dynamics of the wheat cultivar Zhengmai 366 during the booting stage under control (CK, 10/10 °C), chilling (CS, 10/2 °C), and freezing (FS, 10/-2 °C) treatments. Following stress relief, we performed comprehensive analyses on spikelet morphology, physiology, transcriptome, and metabolome. Spikelet development was consistently delayed in both post-cold recovery scenarios, with irreversible damage due to cellular breakdown during FS recovery. Physiological investigations demonstrated that antioxidant enzyme activities and sucrose, hexose, and proline concentration were restored to normal levels after CS recovery but remained suppressed after FS recovery. Furthermore, a progressive increase in indole-3-acetic acid (IAA) levels and a progressive decline in abscisic acid (ABA) levels coincided during the CS recovery, which may facilitate the resumption of spikelet development. Machine learning highlighted sucrose content and the IAA/ABA ratio as primary predictors of grain number. Multi-omics integration further confirmed that the recovery is determined by the sucrose-hexose conversion efficiency and hormonal balance. Collectively, this study revealed that wheat recovery from cold is mediated by coordinated carbon metabolism and hormonal homeostasis. This provided valuable insights toward improving cold tolerance in wheat production.

Soybean mosaic virus (SMV) is a widespread disease that significantly affects the yield and quality of soybean (Glycine max), but our understanding of the molecular mechanisms of resistance to SMV remains limited. In this study, we characterized 27 soybean matrix metalloproteinase (MMP) family members and we report the function and regulatory mechanisms of GmMMP9 in resistance. Soybean plants overexpressing MMP9 exhibited enhanced resistance to SMV, while CRISPR/Cas9-mediated MMP9 homozygous mutants were more susceptible. Staining with DAB and Trypan Blue revealed that MMP9 conferred SMV resistance through production of reactive oxygen species (ROS) and programmed cell death triggered by the hypersensitive response. Furthermore, we determined that MMP9 was involved in endoplasmic reticulum stress induced by SMV via its interaction with the SMV protein 6K1 (SMV-6K1). This interaction was abolished only when all four 6K1-interacting residues in MMP9 were mutated, suggesting that it inhibited SMV-6K1 function via a structural envelopment mechanism. RNA-sequencing analysis of MMP9-overexpressing, knockout, and wild type plants infected with SMV revealed the presence of several differentially expressed genes that were involved in photosynthesis-related processes. In addition, we found that a PSI reaction center subunit N, PsaN, interacted with MMP9. Silencing PsaN in MMP9-overexpressing lines, knockout lines, and wild type plants led to reductions in chlorophyll content, superoxide dismutase activity, H2O2 levels, and the transcriptional expression of ROS-signaling genes, demonstrating that the MMP9-PsaN interaction affected PSI activity and thereby triggered a ROS response. Our findings show that MMP9 is a novel regulator of soybean resistance to SMV, and suggest its potential use for soybean molecular breeding.

Members of the common lichen photobiont genus Trebouxia occur from the arctic to tropical terrestrial habitats however, the mechanisms of environmental stress tolerance in Trebouxia are little understood. Here we studied six species, which belong to the S-clade and A-clade, and were isolated from the lichen-forming fungi Umbilicaria pustulata and U. phaea. These species have demonstrated extensive genomic divergence, particularly in genome regions associated with photosynthesis. Therefore, we hypothesized that they will exhibit differential performance under varying light conditions. We assessed their physiological and transcriptomic responses to short and prolonged exposure to high light (HL). Average levels of Fv/Fm and NPQ showed significant reduction following HL exposure, but this varied among species. Further, only a few differentially expressed genes (DEGs) were found for specific species following exposure to 1 h of HL. On the other hand, there are more DEGs found for those exposed to prolonged HL, particularly photoprotection-associated genes related to NPQ, photosystem II repair, oxygen evolving assembly and biosynthesis of photoprotective pigments. Overall, our findings show that in Trebouxia, the capacity to withstand high light conditions is highly species-specific, and not driven by phylogenetic relatedness or climatic niche preference.

Stomatal conductance (gs) is indicative of plant carbon dioxide uptake via photosynthesis and water loss via transpiration, making it a crucial plant biophysical trait. Direct measurement of gs is labor-intensive and usually not scalable to large fields. Using manual measurements to estimate parameters of gs models is even more labor-intensive and prone to sampling errors. This study aimed to develop an automated pipeline for gs measurement and model calibration using thermal imagery data, which not only disentangles the impacts of genotype-specific stomatal traits and environmental conditions but also enables the prediction of gs in new environments. The methodology involved using simulated thermal imagery data generated from a 3D biophysical model to train a machine learning model that could be applied to real thermal images to predict stomatal model parameters and gs itself. The method was evaluated by comparing predictions against manual gs measurements, all of which were not part of the model training process, as the model was trained against only simulated images. When compared against manual gs measurements using a porometer, the prediction R2 was 0.7, which is likely comparable to the accuracy of the manual porometer-based gs measurements (relative to a leaf gas exchange system). The developed pipeline enables high-throughput gs model parameter calibration and gs estimation.

Proline is a multifaceted amino acid in plants involved in both stress responses and development. Recent studies have shown that knock-out mutants lacking Pyrroline-5-carboxylate dehydrogenase (P5CDH), the enzyme responsible for the second step of proline catabolism, impaired nitrogen remobilisation and carbon allocation to seeds. Here, we demonstrate that seed development is also significantly impaired in p5cdh mutants, particularly from the transition between embryogenesis and maturation. Specifically, the p5cdh mutation leads to an arrest in embryo elongation and a reprogramming of seed metabolism during maturation, resulting in reduced accumulation of storage compounds and compromised acquisition of dehydration tolerance. These effects are further exacerbated under high nitrate conditions. Together, our findings highlight a crucial role for proline catabolism in supporting the ability of maturing embryos to utilize glutamine as a nitrogen source, particularly in response to nitrogen availability.