Journal of Experimental Botany最新文献

The species Alternanthera philoxeroides is a flood-tolerant plant that has to cope with the hypoxic stress under submergence. However, the pith cavity in stems of this species is interrupted and partitioned by low-porosity diaphragms at the nodes. To date little knowledge is available about whether discontinuous pith cavities are functional for internal gas transport in plants. To disclose the role of stem discontinuous pith cavities in internal gas transport, the diffusive transport capacity of O2, the tissue O2 status of intact plants, and the influence of restricting longitudinal O2 supply on whole-plant growth during partial submergence were assessed. We found that stem pith cavities were the main pathway for diffusional supply of molecular O2; blocking only one internode significantly decreased the O2 flux to lower internodes, and the reduced O2 flux translated into reduced growth in partially submerged plants. A major output component of the study is a model that uses normalized tissue dimensions and concentration gradients to establish a fair foundation for comparison of contrasting species under different experimental conditions. We therefore predict that future studies will use this approach to further broaden the scope and value of resistance and flux measurement in target species.

Root system architecture affects water and mineral uptake and is important for plant adaptation to fluctuating nutrient availability. Small signaling peptides and their receptors influence root traits associated with macronutrient uptake. In this study, genome-wide association analyses were performed using 2D images of agar plate-grown Medicago truncatula accessions to understand the impact of GOLVEN10 peptide (GLV10) treatment on three root traits: root tortuosity, lateral root (LR) branch angle, and the gravity setpoint angle (GSA). Upon GLV10 treatment, roots of wild-type M. truncatula Jemalong A17 and R108 accessions showed increased primary root coiling (or tortuosity), increased LR branch angle, and reduced GSA. We identified 88 significant single nucleotide polymorphisms (SNPs) associated with these traits in GLV10-treated plants, distinct from the 163 SNPs in untreated plants. Importantly, the ethylene regulatory pathway was implicated in root tortuosity and LR emergence relative to the primary root. Application of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid reduced root sensitivity to GLV10, while the ethylene signaling mutant sickle was hypersensitive, indicating that GLV10 and ethylene pathways act antagonistically to control root tortuosity. These findings have implications for root gravitropic responses, and the ability of roots to penetrate deeper soil layers for nutrients and water.

Downy mildew, caused by Plasmopara viticola, is one of the most serious grapevine diseases. Resistant grapevines are a well-known tool for mitigating pathogen-caused damage. We evaluated 29 global grapevine cultivars from seven species for sensitivity to P. viticola. Chardonnay, belonging to the sensitive species Vitis vinifera, and Qingdahean, belonging to the well-known resistant species V. riparia, were chosen for further investigation into the resistance mechanism against downy mildew. Unlike Chardonnay, Qingdahean exerted an inhibitory effect on stomatal targeting, suppression of stomatal closure, stomatal penetration of P. viticola, and the development of primary hyphae and haustoria during the early phase of infection, and contained higher levels of malondialdehyde. Malondialdehyde was significantly increased by P. viticola infection, was toxic to the pathogen, and had an interfering effect on stomatal targeting. Furthermore, Qingdahean resisted pathogen invasion through the rapid induction of guard cell death and hypersensitive responses of other cell types. These findings suggest that resistance to P. viticola in V. riparia consists of layered stomatal immunity in addition to the well-known hypersensitive response, which is overcome by the pathogen in V. vinifera.

Plant callus cells possess a great capacity to regenerate organs or even whole plants. The mechanisms by which these cells maintain a proliferative state while retaining their pluripotent identity are poorly understood. By taking a multi-omics approach integrating epigenetic regulation (via chromatin immunoprecipitation and sequencing) with transcriptional output, we identify two complementary strategies that support callus cell pluripotency. First, callus cells prevent differentiation by promoting proliferation through activating cell cycle genes, and concurrently repress differentiation-promoting factors via H3K27me3. Second, callus cells exhibit a unique transcriptional profile enriched in diverse developmental regulators, thereby maintaining a primed pluripotent state that enables a rapid regenerative response. This strategy relies on a mechanism to silence the pluripotency network in response to regenerative stimuli, allowing a single developmental pathway to predominate. To test whether the Polycomb Repressive Complex 2 (PRC2), which mediates H3K27me3 silencing, is essential for maintaining callus identity and regenerative capacity, we analyzed the transcriptional state of Arabidopsis thaliana wild-type and PRC2 mutant emf2 calli. In emf2 mutants, many differentiation-associated transcription factors were up-regulated, and regenerative capacity was severely impaired. Our findings provide new insight into how pluripotency is regulated. We propose a novel model in which PRC2 governs callus identity and regenerative potential.

Abscisic acid (ABA), a phytohormone that affects key biological processes, is best known for causing stomata closure to protect plants against environmental stresses. The prevailing mechanism for ABA perception is through the PYL/PYR/RCAR family of proteins but reports of other ABA-interacting proteins such as the guard cell outward rectifying K+ channel (GORK), have encouraged the search for more ABA-sensitive proteins. Here, we identified a similar ABA-interacting site as GORK, in an Arabidopsis thaliana ANTHRANILATE SYNTHASE (ASA2). We found that asa2 mutant plants have obvious aberration in ABA-dependent stomata closing. Leaf transcriptomics revealed significantly fewer ABA-induced DEGs in asa2-1 as compared to Col-0. ABA- and other hormone-related terms were also under-represented, indicating an overall reduced genomic sensitivity to ABA. Computational analysis hinted plausible ABA interaction at the predicted site and both indirect and direct in vitro interaction studies showed that ASA2 could interact with ABA in a specific and ligand dependent manner. Importantly, single amino acid substitutions at the ABA site resulted in various degrees of reduced ABA affinities. Further examination of how ABA interaction affects the enzymatic activity of ASA2 and the flow of information in the chloroplast could reveal molecular targets for agrochemical design that will improve plant resilience.

Cotton fiber derived from the ovule epidermis provides a natural source for the textile industry. Transcriptional features of the ovule epidermis contribute critical signals and guide fiber development. This study applied 10× Genomics Visium spatial transcriptome platform to cotton ovules at one day post-anthesis, generating high-resolution, tissue-specific gene expression profiles during early ovule development. Following data normalization, dimensionality reduction, and clustering with Seurat, ovule cross-sections were segmented into seven distinct tissue groups based on anatomical features: nucellus/embryo sac, inner integument micropylar end, inner integument chalaza, outer integument chalazal end, outer integument chalaza, outer integument micropylar end, and funicle. These clusters reveal unique transcriptional signatures that closely correspond with the developmental functions of each tissue region. The cotton fiber condensation region on outer integument chalazal end is characterized by primary cell biosynthesis while the outer integument micropylar end is enriched with lipid transportation associated with fiber yield. The resulting 1-DPA cotton ovule spatial transcriptome atlas (1-COSTA) captures key gene expression patterns linked to fiber and lint yield regulation. To facilitate data exploration, the 1-COSTA database was established with a user-friendly web interface built on R Shiny Server, enabling researchers to access core Seurat visualization and analysis tools including 3D expression visualization of genes in a code-free manner. This resource offers an invaluable reference for understanding spatial gene regulation in cotton fiber development and seed yield.

Genetics studies based on end-of-season measurements focus only on the outcome of a complex and dynamic process. Uncovering the genetic basis underlying the temporal dynamics of plant height will enhance our understanding of the genotype-to-phenotype relationship. Here, we conducted functional mapping to investigate the temporal dynamics of plant height using the time-series data extracted from UAV-based RGB imagery from two sorghum populations. Significant correlations were found between the UAV-derived measurements and manual measurements. We modeled the growth trajectory using a logistic function. Among QTLs identified by mapping with the growth curve parameters as derived traits, several were co-localized with known genes controlling plant height. To further visualize the temporal patterns of genetic effects, we used the logistic function to estimate each genotype's height at a five-day interval. Genome scans of the model-estimated heights detected QTLs with dynamic effect changes across development. Persistent QTLs, co-localizing with Dw1, Dw2, Dw3, and qHT7.1, were detectable starting from 40 days after planting, whereas several transient QTLs were only detectable within specific shorter periods or at some growing seasons. These findings enabled us to generate a conceptual figure to depict six potential dynamic patterns of persistent and transient QTLs underlying growth trajectories.

Root-exuded organic acids are crucial in mitigating iron (Fe) and phosphorus (P) deficiencies. Their biosynthesis and secretion require significant metabolic investment. Recent studies have shown that roots can also uptake exudates. We hypothesized that citric acid uptake increases under Fe and P deficiencies, declines over time, and contributes to primary metabolism. We investigated citric acid uptake, translocation, and metabolization in Fe- and P-deficient in hydroponically-grown tomato plants. We applied 13C-labeled citric acid analysed through bulk stable isotope and compound-specific stable isotope analysis. Physiological parameters, root morphology, and elemental composition were also assessed. Deficient plants showed reduced P and Fe content, reduced photosynthesis, altered root morphology and an altered citric acid uptake, which could not be attributed to morphological differences. Iron deficiency reduced citric acid uptake, indicating its role in rhizospheric Fe mobilization, while P deficiency increased the uptake emphasizing resource use efficiency. Unexpectedly, citric acid uptake increased with plant development. In Fe deficiency, citric acid-derived carbon is allocated to secondary metabolites, while in P deficiency, it supports the TCA and GS-GOGAT cycles. This study is the first to demonstrate citric acid uptake as a multifunctional process, underscoring its critical role in plant responses to nutrient starvation, especially under P deficiency.

Isoprenoids (also called terpenoids) are a large group of natural chemical compounds. Some isoprenoids are specialized metabolites that give smell and taste to plants and provide protection against herbivores and pathogens. Production of these particular substances is specific to certain species and plant families and hence is classified as secondary metabolism. In addition, numerous isoprenoids perform essential cellular functions for example chloroplast isoprenoids give rise to photosynthetic pigments, electron transporters, and membrane modifiers in the thylakoid membrane to adjust the correct level of photosynthetic performance and prevent oxidative damage in the chloroplasts. Similarly, some cytoplasmic isoprenoids serve a key role in the primary cell metabolism of all eukaryotic cells, forming membrane microdomains (sterols), serving as lipid anchors for prenylated proteins (geranylgeranyl and farnesyl groups), and co-factors of protein glycosylation (dolichols). The non-steroid isoprenoids (prenyl groups of proteins and ubiquinone, dolichols) and their role in the plants are far less described than sterols. In this review, we present a summary of the knowledge on protein prenylation but also farnesol and geranylgeraniol turnover in cytoplasm in the context of membrane structure, biochemistry, plant physiology, and development in Arabidopsis model plant and other species.