Plant Direct最新文献

Plants require cytochrome P450 reductase (CPR) to supply two electrons for cytochrome P450 monooxygenase enzymes (P450) to react with an organic substrate. The transfer of electrons to the P450 active site in the P450 catalytic site relies on a robust and intricate CPR:P450 complex in the endoplasmic reticulum membrane. Transgenic Arabidopsis plants carrying CYP81A12 from Echinochloa phyllopogon, which metabolizes a broad spectrum of herbicides, were crossed with CPR knockout atr1 or atr2 mutant lines. Homozygous gene knockout was confirmed using PCR, and gene copy number of CYP81A12 was determined using ddPCR. Arabidopsis lines expressing CYP81A12 in combination with atr1 or atr2 knockout were used for herbicide dose-response and metabolism studies. Knocking out ATR1 in transgenic Arabidopsis CYP81A12 significantly reduced herbicide resistance. Transgenic mutant plants (CYP81A12 atr1-b) had a 3.6-, 5.6-, 6.8-, and at least 26-fold reduction in resistance to mesotrione; 2,4-D; penoxsulam; and chlorsulfuron, respectively, in the dose-response assay. Knockouts of ATR2 also decreased herbicide resistance but to a lower magnitude than ATR1. These results corroborate ½ MS medium assay, and herbicide resistance reduction was observed for additional herbicides including bensulfuron-methyl, propoxycarbazone-sodium, and bentazon. Our findings highlight the importance of CPRs in metabolic herbicide resistance in plants by identifying that a single CPR knockout can reverse herbicide resistance. The different CPRs found in weeds have potential as target genes to manage metabolic herbicide resistance evolution. We further provide an in-depth exploration of the evolutionary implications in weed management arising from the results.

Cardosins A and B are aspartic proteinases found in cardoon that share high sequence similarity, accumulate in the vacuole, and are responsive to stress conditions. These proteins have a 100 amino acid domain termed Plant Specific Insert (PSI), responsible for their vacuolar targeting. Different PSIs mediate different routes to the vacuole: PSI from cardosin A mediates a Golgi-independent route, while PSI from cardosin B (PSI B) mediates a conventional ER-to-Golgi pathway. It is known that stress can impact protein sorting, shifting it from the conventional pathway to a Golgi-independent route. As such, in this work we investigated the expression and localization of PSI B in Arabidopsis plants overexpressing PSI B-mCherry submitted to different abiotic stress conditions (saline, hydric, oxidative and Zn). The results revealed that the plants expressing PSI B showed increased PSI B accumulation under saline stress but decreased accumulation under hydric stress. PSI B accumulation was detected in the vacuole, but also in Endoplasmic Reticulum-derived vesicles (ER bodies-rod-shaped or spindle-like compartments within the ER that store and transport proteins), indicating a shift from the conventional PSI B-mediated route. Altogether, these findings highlight the role of PSI B in promoting plant fitness and adaptation to abiotic stress by modulating protein trafficking.

Houttuynia cordata is an important medicinal and vegetable crop in Southwest China. Due to the accumulation of heavy metal ions such as lead ions (Pb²⁺) in H. cordata, consumption of this plant carries risks, such as ingestion of lead-contaminated H. cordata, may lead to Pb²⁺ bioaccumulation, which is associated with developmental retardation, endocrine disruption, and impairments to immune and neurological functions. In order to screen H. cordata germplasm for low Pb²⁺ absorption and identify the Pb²⁺ adsorption-related agronomic traits and molecular markers, the genetic diversity of a germplasm resource of H. cordata comprising collected 72 accessions was comprehensively evaluated based on agronomic traits and Pb²⁺ contents in the underground stems of the plant. Further, intersimple sequence repeats (ISSR) markers and generalized linear model (GLM) correlation analyses were performed to identify the ISSR loci related to the Pb²⁺ absorption. Ward clustering analysis grouped the 72 accessions of H. cordata into five major classes through analysis of morphological traits. Combined analysis of the Pb²⁺ contents of underground stems with the phenotypic traits revealed significant changes in members within the five classes, indicating that the Pb²⁺ content significantly affected the results of the evaluation of agronomic traits. Greyscale analysis and subsequent verification revealed that the underground stem thickness was closely related to the Pb²⁺ absorption. Based on ISSR markers and subsequent verification, two loci, namely, Locus 21 and Locus 29, were found to have better screening effects on germplasms with low Pb²⁺ adsorption. The accessions that did not carry these two loci in the genome generally exhibited low lead ion adsorption. This study presents a faster marker-based screening for H. cordata plants that are safer for consumption.

Heat-drought stress during the late development of soybean seeds (Glycine max [L.] Merr.) adversely affects chlorophyll degradation, resulting in green seeds with low physiological quality. This study aimed to relate chlorophyll fluorescence, oxygen consumption rates, and germination characteristics in green and yellow soybean seeds produced under heat-drought stress conditions. Seeds produced under favorable growth conditions were used as controls. Seed chlorophyll fluorescence was measured as well as individual seed respiratory activity by measuring oxygen levels during germination over 90 h at 25°C. Results indicated that green seeds, with the highest chlorophyll fluorescence, exhibited the lowest initial metabolic rates and germination percentages. Additionally, green seeds took longer to consume 50% of the available oxygen, requiring 45.90 h compared to 25.54 h for yellow seeds and 19.63 h for control seeds. Germination rates and embryonic axis lengths were significantly lower for green seeds (11.1% germination and 0.59 cm length) compared to yellow seeds (65.4% and 1.04 cm) and control seeds (83.3% and 1.44 cm). A negative correlation was found between chlorophyll fluorescence and both metabolic rates and embryonic axis length, indicating that heat-drought stress severely impacts chlorophyll degradation, oxygen consumption, metabolic rates, and germination in green soybean seeds.

Arabinokinase (ARA1) is a key player in the recycling pathway of the major cell wall component L-arabinose (L-Ara). The enzyme catalyzes phosphorylation of L-Ara to L-arabinose-1-phosphate, which is then converted into UDP-L-arabinopyranose (UDP-L-Arap) by UDP-sugar pyrophosphorylase (USP) followed by conversion into UDP-L-arabinofuranose (UDP-L-Araf) by UDP-arabinopyranose mutases (UAM) before it is incorporated into cell wall polymers. While this pathway is typically nonessential for plant development, a threefold accumulation of UDP-L-Arap can lead to toxicity. To investigate this, we generated Arabidopsis thaliana lines overexpressing the kinase domain of ARA1 (ARAK1-OE) and examined their response to L-Ara feeding. ARAK1-OE seedlings revealed dose-dependent root growth retardation and cell death. The presence of 3 mM L-Ara resulted in an eightfold increase in UDP-L-Arap levels compared with nonfeeding conditions. Interestingly, wildtype seedlings showed no visible phenotype regardless of available L-Ara and despite the increase in UDP-L-Arap, suggesting a critical threshold for the observed phenotype. Cell walls of ARAK1-OE revealed a stronger attachment of arabinogalactan proteins (AGPs). Gene expression analysis from seedlings grown on 3 mM L-Ara implied that accumulation of UDP-L-Ara in ARAK1-OE triggers cell death resembling pathogen-induced hypersensitive responses. Overall, our findings demonstrate that modest increases in UDP-L-Arap levels can lead to significant phenotypic effects, including programmed cell death. This study highlights the role of arabinokinase in regulating L-Ara flux into nucleotide sugars, preventing arabinose-induced toxicity, and offers novel insights into the regulatory function of arabinokinase in cell wall biosynthesis and plant stress responses.

In angiosperms, such as Arabidopsis, silique removal can reverse developmental arrest and reactivate inflorescence meristems, illustrating that post-fertilization growth cessation is a plastic process rather than terminal differentiation. However, it remains unclear whether a similar growth arrest plasticity occurs in conifers, where mature seed cones typically undergo terminal differentiation as determinate structures. In this study, we analyzed the proliferated seed cones of Larix kaempferi, which exhibited vegetative shoots sprouting from their central axes. We collected and examined both the proliferated and normal seed cones from a second-generation seed orchard. The proliferated seed cones were longer, produced more seeds, had a smaller seed scale spacing, and displayed enhanced secondary growth compared to normal seed cones. Our analysis suggested that the proliferated seed cones underwent a transition from reproductive to vegetative growth after seed production, indicating that proliferative arrest in these cones can be disrupted. Based on structural and developmental comparisons with Arabidopsis thaliana, the proliferated seed cones exhibit unexpected plasticity: their growth arrest is reversible rather than terminal, similar to silique-removal-induced meristem reactivation in Arabidopsis. This suggests that conifer cones retain the ability for delayed differentiation, not only offering new insights into conifer development but also a potential conifer model for studying reproductive-to-vegetative phase transition.

The role of cytokinin among plant hormones in seed development remains largely unknown. The Arabidopsis response regulator 21 (ARR21) is one of the cytokinin response regulators and a Type-B ARR with a nuclear localization signal and a GARP motif similar to the MYB-like DNA-binding domain. ARR21-sGreen fluorescent protein (GFP) signals were localized within the nucleus, and ARR21 showed the highest expression levels in developing seeds. In addition, histochemical analysis revealed ARR21 expression in the silique coats, chalazal seed coat, chalazal endosperm, and throughout the developing seed at 6 days after pollination. Two independent mutants were generated using the CRISPR/Cas9 system: arr21-3 (51 bp in-frame deletion) and arr21-4 (2 bp insertion). The seed size and weight of the arr21 mutants decreased by an average of 10.7% and 37%, respectively, compared to the wild-type (WT). In arr21 mutants, the cotyledon length of embryos and the size of seed coat cells were reduced. Seed-specific overexpression of ARR21 in arr21-4 restored the seed length to WT levels. This study suggests that ARR21 regulates seed size by functioning in the chalazal endosperm and embryo, thereby providing insights into the role of cytokinin in seed development.

Plant roots are the critical interface between plants, soil, and microorganisms, and respond dynamically to changes in water availability. Although anatomical adaptations of roots to water stress (e.g., the formation of root cortical aerenchyma) are well documented, it remains unclear whether these responses manifest along the length of individual roots under both water deficiency and water overabundance. We investigated the anatomical responses of Tripsacum dactyloides L. to both drought and waterlogging stress at high spatial resolution. Nodal roots were segmented into one-centimeter sections from the tip to the base, allowing us to pinpoint regions of maximal anatomical change. Both stressors overall increased the proportion of root cortical aerenchyma, but metaxylem responses differed: waterlogging increased the proportion of the stele that was occupied by metaxylem with fewer but larger vessels. Drought significantly increased root hair formation within two centimeters of the root tip. The most pronounced anatomical changes occurred 3-7 cm from the root tip, where cortical cell density declined as aerenchyma expanded. These findings highlight spatial variation in root anatomical responses to water stress and provide a framework that can inform sampling protocols for various other data types where sampling effort is limiting (e.g., microbiome, transcriptome, proteome).

Current efforts to detect and evaluate crop resistance to insect pests are limited by traditional phenotyping methods, which are time-consuming and highly variable. Sugarcane aphid (SCA; Melanaphis sacchari) is a major pest of sorghum in North America that has emerged over the last decade and negatively impacts plant growth and development. The spectral reflectance data in visible, near infrared and shortwave infrared range (VIS-NIR-SWIR; 400-2500 nm) have been used to measure plant traits related to stress responses, nutrient dynamics, and physiological status. We examined the potential of spectral features (VIS-NIR-SWIR) to improve the current phenotyping methods in monitoring sorghum resistance mechanisms to SCA. We used eight sorghum lines that displayed varied levels of resistance to SCA and collected data from control and aphid-infested plants. Spectral feature data were collected using a leaf spectrometer, while plant physiological and chlorophyll fluorescence parameters were measured with LICOR and MultispeQ devices. The random forest classifier model differentiated the control and aphid-infested plants with a high accuracy of 87.4% with important spectral features in the VIS-NIR spectral range, particularly from 508 to 573 nm and 715 to 728 nm. The spectral indices exhibit significant difference in Greenness Index and Plant Senescence Reflectance Index in aphid-infested susceptible lines (BTx623, SC1345) compared with control plants. In addition, plant physiological parameters, such as stomatal conductance and chlorophyll fluorescence, showed significantly higher value for aphid-infested resistant line (Tx2783) compared with susceptible line (BTx623) in both treatments. Further, a partial least square regression model demonstrated medium predictive capability for plant physiological parameters related to fluorescence. In summary, spectral features at VIS-NIR range demonstrated promising results in differentiating aphid-infested sorghum plants. This is a proof-of-concept study on potential of spectral sensing to develop an effective monitoring and phenotyping plant resistance to aphids.

The apoplastic space surrounding plant cells, encompassing the cell wall matrix, extracellular spaces, and xylem, is one of the least understood compartments within plant tissues due to its lack of limiting membranes and its unavoidable damage upon tissue homogenization. Using a streamlined vacuum-infiltration/centrifugation protocol to enrich for the Arabidopsis apoplastic fluid (APF) combined with in-depth tandem mass spectrometry, we provide an improved view of its proteome that includes over 1500 proteins possibly assigned to this compartment with minimized cytosolic contamination. Included are large and varied collections of polypeptides associated with cell wall metabolism, oxido-reductase reactions, cell-cell signaling, proteolysis, and pathogen protection via basal defense pathways. While numerous apoplast proteins were predicted to house N-terminal signal peptide sequences that direct extracellular secretion, many did not, suggesting widespread use of non-classical export route(s). Among APF constituents are numerous pathogenesis-related proteins, glycosidases, aspartyl and subtilisin-type serine proteases, and the complement of subunits that assemble the core particle of the 26S proteasome. When this APF proteome is compared with those based on two prior isolation methods, a consensus collection of 338 polypeptides emerges that offers a comprehensive view of the core APF proteome that manages the cell wall and interfaces with the environment.