Plant Direct最新文献

Phototropic bending of plants towards a light source allows them to position their photosynthetic tissues to optimize light capture. In light-grown (de-etiolated) Arabidopsis seedlings, phototropic bending of the hypocotyl is inhibited by light with a high red:far-red ratio (HRFR) and high levels of blue light (HBL). This occurs via activation of the phytochrome B (phyB) and cryptochrome 1 (cry1) photoreceptor signaling pathways. Both phyB and cry1 act upstream of PHYTOCHROME INTERACTING FACTOR (PIF) transcription factors, which are required for hypocotyl bending in light-grown seedlings. Presently, it is not known whether other pathways are involved in the inhibition of PIF-mediated phototropism in light-grown seedlings. To address this, we conducted a screen to identify mutants with increased phototropic bending relative to wild type in HRFR + HBL conditions. Through this screen, we identified EARLY FLOWERING 3 (ELF3), a member of the Evening Complex (EC), as a key inhibitor of phototropic bending in green seedlings. We show that both ELF3 and LUX, another component of the EC, inhibit phototropic bending upstream of PIF4/PIF5. Furthermore, we show that phototropic bending in Arabidopsis seedlings is subject to circadian regulation in an ELF3-dependent manner. Finally, we provide evidence that ELF3 in the grass Brachypodium distachyon also affects phototropism but in an opposite way than in Arabidopsis.

In apple (Malus domestica), flowering is repressed by the phytohormone gibberellin (GA) and high temperatures (> 27°C), but the molecular mechanisms underlying this repression remain unknown. In Arabidopsis thaliana (Arabidopsis), GA and temperature signaling converge on DELLA protein regulation, with both factors promoting DELLA degradation through independent 26S proteasome-mediated pathways. Here, we tested whether high-temperature-induced DELLA degradation is conserved in apple. Using the heterologous systems Arabidopsis and Nicotiana benthamiana, we characterized the function of the apple DELLA protein DELLA REPRESSOR OF ga1-3 (MdRGL1a) and found that high temperatures promote its degradation via a 26S proteasome-dependent mechanism. Additionally, MdRGL1a interacts with apple orthologs of Arabidopsis CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1) and SUPPRESSOR OF phyA-105 2 (SPA2), components of an E3 ubiquitin ligase complex that mediates protein ubiquitination and degradation. These findings suggest a conserved mechanism of temperature-induced DELLA degradation between apple and Arabidopsis. The degradation of MdRGL1a may underlie flowering suppression in apple under high temperatures, providing molecular insights that could aid in developing strategies to stabilize apple and other crop production in the face of climate change.

Plant diseases caused by pathogenic microorganisms result in significant damage to agriculture. Lactic acid bacteria (LAB), in particular strains of Lactiplantibacillus plantarum (L. plantarum), are used as one of the biocontrol methods against plant pathogenic bacteria due to high antagonistic activity associated with their metabolic potential. We have investigated the influence of nutrient medium components (various carbon and nitrogen sources) and cultivation conditions (temperature, duration, and pH) of L. plantarum strains on the level of their antagonistic activity against the test strains of plant pathogenic bacteria. The antimicrobial activity of LAB supernatants was maximal in the presence of 3% (30 g/L) sucrose as the main carbon source and 1% (10 g/L) tyrosine as the main nitrogen source in the nutrient medium against all investigated test strains of PPB. However, the use of such a carbon source as galactose or arabinose led to a decrease or even absence of antimicrobial properties of LAB against phytopathogenic bacteria. The optimal conditions for cultivation of lactobacilli were determined: cultivation temperature +30 ± 1°C, pH 7.8, and duration 72 h. Strains of L. plantarum 13c and 21c caused zones of inhibition in test pathogens from 298 to 291 mm. Whereas during 24-h cultivation of LAB strains, their antagonistic activity was significantly lower, and the zones of inhibition decreased by 30%. The duration and temperature had a significant effect on increasing the antagonistic activity of L. plantarum strains, in contrast to the pH of the medium (p ≥ 0.05).

Microalgae are promising sources to sustainably meet the global needs for energy and products. Algae grow under different trophic conditions, where nutritional status regulates biosynthetic pathways, energy production, and growth. The green alga Chromochloris zofingiensis has strong economic potential because it co-produces biofuel precursors and the high-value antioxidant astaxanthin while accumulating biomass when grown mixotrophically. As an emerging reference alga for photosynthesis, metabolism, and bioproduction, C. zofingiensis needs a defined, optimized medium to standardize experiments during fast growth for batch cultivation. Because the interplay of glucose treatment (+Glc) and mineral deficiency influences photosynthesis, growth, and the production of lipids and astaxanthin, we designed a replete nutrient medium tailored to the C. zofingiensis cellular ionome. We combined inductively coupled plasma mass spectrometry (ICP-MS) and +Glc growth curves to determine a medium that is nutrient replete for at least 5 days of +Glc logarithmic growth. We found that there are high nutritional needs for phosphorus and sulfur during mixotrophy. Iron was the only element measured for which the cellular concentration correlated with exogenous concentration and was iteratively adjusted until the cellular ionome was consistent through the logarithmic growth phase. This Chromochloris-Optimized Ratio of Elements (CORE) medium supports fast growth and high biomass and lipid accumulation without causing excess nutrient toxicity. This defined, nutrient-replete standard is important for future C. zofingiensis investigations and can be adapted for other species to support high biomass for batch cultivation. The method used to develop CORE medium shows how ionomics informs replicable media design and may be applied in industrial settings to inform cost-effective biofuel production.

Weedy rice, a wild relative of cultivated rice, is highly stress-resistant and proliferates in paddy fields. In this study, 353 weedy rice accessions were analyzed to identify salt-tolerance genes using population evolution analysis, phenotypic screening, genome-wide association studies (GWAS), transcriptome analysis, haplotype characterization, gene knockout experiments, and Na⁺ and K⁺ ion flux assays. Population structure analysis classified the accessions into six distinct groups. Three salt-tolerant accessions-HW131, HW136, and HW119-were identified based on leaf rolling degree (LRD), leaf withering degree (LWD), chlorophyll content (ChlC), and nitrogen content (NC) traits. GWAS and transcriptome data pinpointed LOC_Os06g39270 and LOC_Os06g11860 as candidate salt-tolerance genes. Haplotype analysis and qPCR confirmed two major haplotypes: AHap2 and BHap1. A 2-bp deletion (TC) at position 818 bp in LOC_Os06g11860 was associated with severe salt sensitivity (phenotypic grade 7), whereas the wild-type exhibited strong tolerance (grade1). Knockout mutants exhibited significantly increased Na⁺ and K⁺ flux across mesophyll cell membranes compared to wild-type plants, validating LOC_Os06g11860 (OsERFH1) as a crucial salt-tolerance gene. This study provides novel genetic insights into salt-stress adaptation in weedy rice, paving the way for breeding enhanced salt-tolerant varieties.

Resistance to 2-methyl-4-chloro-phenoxyacetic acid (MCPA) was recently confirmed in a population of green pigweed (Amaranthus powellii) from Dresden, Ontario, Canada, with a resistance factor of 4.4. Resistance to synthetic auxin herbicides in Amaranthus species has previously been linked to non-target site resistance mechanisms with low-level resistance factors (< 10). Based on this information, an investigation into the mechanism of resistance to MCPA was conducted in this population of green pigweed. No significant differences in absorption, translocation, and metabolism of ¹⁴C-MCPA existed between the resistant and a susceptible population of green pigweed. An RNA-Sequencing experiment to identify differentially expressed genes also confirmed this result. Genes that were differentially expressed in the resistant population were linked to target site modifications. A single nucleotide polymorphism (SNP) conferring a leucine to phenylalanine substitution was identified in auxin response factor (ARF) 9. This mutation may be in the Phox and Bem1p (PB1) domain in ARF9, which facilitates the interaction between ARFs and Aux/IAA repressor proteins. The results demonstrate that the mechanism of resistance to MCPA is not a non-target site mechanism and may be linked to a target site modification. Specifically, a SNP in ARF9 could disrupt the interaction between ARF9 and other Aux/IAAs, which could prevent ubiquitination of Aux/IAAs and subsequent lethal action of MCPA.

Amino acid transporters play crucial roles in plant nitrogen metabolism but also in defense responses. AAT_Rhg1, an apparent amino acid transporter encoded by Glyma.18g022400 (Rhg1-GmAAT) at the soybean Rhg1 locus, contributes to resistance to soybean cyst nematode (SCN), although the in planta function of AAT_Rhg1 remains elusive. In this study, we discovered that overexpression of Rhg1-GmAAT in soybean roots enhances the betalain pigment synthesis driven by a RUBY transgene cassette, potentially through its transporter activity affecting tyrosine levels and amino acid homeostasis. Silencing Rhg1-GmAAT also moderately increased betalain accumulation, while co-overexpression of Rhg1-GmAAT and GmRBOHG (encoding an AAT_Rhg1-interacting NADPH oxidase) blocked the betalain phenotype, indicating a complex role of AAT_Rhg1 in regulating cellular metabolism. Soybean AAT_Rhg1 did not show a betalain accumulation phenotype when co-overexpressed with RUBY in Nicotiana benthamiana leaves, suggesting that soybean AAT_Rhg1 functions differently in N. benthamiana. In soybean, expression of AAT_Rhg1 proteins with mutations at conserved residues D122A or Y268L mitigated or enhanced the betalain phenotypes, respectively, suggesting that these residues are important for AAT_Rhg1 function. This study advances our understanding of AAT_Rhg1 while presenting a novel strategy for enhancing betalain biosynthesis by modulating the transport and homeostasis of amino acids.

Gall-inducing insects manipulate host plant development, redirecting cellular fate and physiological processes to form novel structures. This phenomenon is even more intriguing when the host itself is a holoparasitic plant with minimal photosynthetic capacity. In the stem of Cuscuta campestris, the weevil Smicronyx madaranus forms galls that unexpectedly activate photosynthesis, in contrast to the typical suppression of photosynthetic activity observed in leaf-derived galls. This reversal of the usual source-to-sink transition highlights a unique form of insect-induced organogenesis. To elucidate the underlying mechanisms, we performed transcriptomic, histological, and physiological analyses of these galls. RNA-seq across four developmental stages identified differentially expressed genes and associated gene ontology terms. Consistent with histological observations, genes related to cell division and the cell cycle were upregulated in early stage but decreased as the gall matured. Similar to leaf-derived galls, we found high expression of PLETHORA and meristem-related homeobox genes in early gall development, suggesting that induction of cell division is involved in various gall types. Interestingly, the expression of genes related to floral organ development increased through gall development. However, their expression patterns showed a marked temporal shift: Floral organ identity genes were highly expressed at the initial gall stage, whereas floral transition genes were activated later. This suggests that the weevil triggers ectopic activation of the flowering pathway in non-floral tissues, potentially redirecting the typical flowering cascade to drive gall formation. Consistent with previous findings, photosynthesis-related genes were highly expressed in later stage of galls, despite the host being a holoparasitic plant. Shading experiments confirmed that photosynthesis is crucial for both gall and the weevil growth. This study highlights how gall-inducers can co-opt host resources and genetic pathways, offering new insights into the complexity of plant-insect interactions.

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.