Waterlogging stress significantly compromises crop growth and yield. In cucumber (Cucumis sativus L.), the formation of adventitious roots (ARs) is a critical morphological adaptation for survival. While ethylene is know...Waterlogging stress significantly compromises crop growth and yield. In cucumber (Cucumis sativus L.), the formation of adventitious roots (ARs) is a critical morphological adaptation for survival. While ethylene is known to promote AR formation under waterlogging, the interplay between ethylene and abscisic acid (ABA) signaling remains complex. In this study, we modulated ethylene levels using the precursor 1-aminocyclopropane-1-carboxylic acid (ACC) and the inhibitor aminoethoxyvinylglycine (AOA) to investigate the underlying transcriptional networks. RNA-seq analysis of hypocotyls under waterlogging (WL), WL+ACC, and WL+AOA conditions identified a set of ethylene-responsive genes, including the transcription factor CsWRKY41. Functional characterization revealed that CRISPR/Cas9-mediated mutation of CsWRKY41 significantly impaired AR formation, whereas its overexpression enhanced it. Mechanistically, CsWRKY41 directly binds to W-box elements within the promoters of the ABA receptor gene CsPYL4 and the phosphatase gene CsPP2C24, acting as a transcriptional activator of CsPYL4 and a repressor of CsPP2C24. Furthermore, CsPYL4 physically interacts with CsPP2C24 to modulate ABA signaling. Overexpression of CsPYL4 was found to upregulate the peroxidase gene CsPrx2 and increase H2O2 accumulation, thereby facilitating AR development. Collectively, our findings elucidate a novel molecular mechanism wherein ethylene orchestrates AR formation via the CsWRKY41-CsPYL4-CsPP2C24 module to mitigate waterlogging stress.
Cleistogamy, or self-fertilization of a closed flower, can limit unintended gene flow and may contribute to varietal purity in rice (Oryza sativa), with potential value for transgene containment. We previously identified...Cleistogamy, or self-fertilization of a closed flower, can limit unintended gene flow and may contribute to varietal purity in rice (Oryza sativa), with potential value for transgene containment. We previously identified the natural cleistogamous mutant lodiculeless spikelet (ld). Here, using map-based cloning, we show that ld carries a 4.6-kb deletion encompassing the entire MICRORNA806a (MIR806a) precursor and the upstream region of the MIR172b locus. CRISPR/Cas9-mediated editing of the MIR806a or MIR172b locus demonstrated that the loss of accumulation of miR172b, but not miR806a, is responsible for the cleistogamy phenotype of ld plants. Small RNA sequencing confirmed that miR172b is nearly absent in ld mutants. Among the five APETALA 2 (AP2)-like genes harboring miR172b target sites, only SUPERNUMERARY BRACT (SNB) transcripts accumulated to significantly higher levels in young ld panicles than the wild type. Prime editing of the miR172-binding site in SNB generated a miR172-resistant SNB transcript isoform that reproduced the vestigial lodicule phenotype, indicating that the derepression of SNB transcript accumulation is sufficient to alter lodicule development. Histological analysis of rice harboring the GUS reporter gene driven by the MIR172b or SNB promoter revealed a strong overlap between the MIR172b and SNB expression domains in developing lodicules, supporting their regulatory relationship. Together, these results identify the miR172b-mediated repression of SNB transcript abundance as an important regulatory module for lodicule development and cleistogamy in rice. The agronomically neutral ld alleles represent valuable genetic resources for developing cleistogamous rice cultivars.
As essential components of eukaryotic genomes, transposable elements (TEs) play crucial roles in shaping genome architecture and driving evolution. To explore TE adaptation across diverse plant genera and understand thei...As essential components of eukaryotic genomes, transposable elements (TEs) play crucial roles in shaping genome architecture and driving evolution. To explore TE adaptation across diverse plant genera and understand their impact on genome diversity, we conducted a comparative mobilome, methylome and sRNAome using the Solanaceae family as a model. Our research indicates that TEs exhibit limited long-term conservation of individual families during diversification within Solanaceae, coupled with pronounced copy-number inequality among TE families. TEs contribute to the expansion of host genome size independently of whole-genome duplication. While under the repression of host gene silencing strategies, such as copy number- and context-specific DNA methylation, TEs coevolve with and adapt to the host genomes. Notably, TEs acquire silencing-related gene fragments from their hosts, thereby enhancing their adaptive capabilities. Furthermore, specific TE sub-families trigger heterochromatin formation, while repeated insertions of TEs within centromeres result in the erosion of repetitive centromeric sequences. In summary, our phylo-mobilome analysis sheds light on TE dynamics and the intricate coevolution between TEs and their host genomes within the Solanaceae family.
Phosphoenolpyruvate carboxylase (PEPC) catalyzes the first irreversible reaction of the CO2 concentrating mechanism (CCM) in C4 photosynthesis. Engineering C4 photosynthesis into the C3 plant rice (Oryza sativa) to incre...Phosphoenolpyruvate carboxylase (PEPC) catalyzes the first irreversible reaction of the CO2 concentrating mechanism (CCM) in C4 photosynthesis. Engineering C4 photosynthesis into the C3 plant rice (Oryza sativa) to increase photosynthetic efficiency requires sufficient activity and proper regulation of PEPC. In previous studies, in vivo PEPC activity remains low despite substantial in vitro activity. Here, we tested the activity and regulation of PEPC expressed in rice using either the coding (cDNA) or genomic (gDNA) sequences of the C4 photosynthetic isoform of PEPC from maize (Zea mays) driven by the ZmPEPC promoter, termed cDNAlines and gDNAlines, respectively. We quantified PEPC enzyme characteristics in vitro, estimated in planta PEPC activity using 13CO2 labeling, and assessed diel phosphorylation status. Both cDNAlines and gDNAlines showed higher PEPC activities than wild-type rice, but in planta activity was <2.1% of in vitro activity. PEPC from gDNAlines had similar affinity to HCO3- but decreased affinity to phosphoenolpyruvate (PEP) in the absence of the positive effector glucose-6-phosphate. In contrast to maize, PEPC in rice lines was primarily phosphorylated in the dark. Estimated PEP concentrations in rice were higher than those required for half-maximal activity of maize PEPC, suggesting that PEP availability was not limiting. The estimated malate pool was higher than required to inhibit phosphorylated and especially dephosphorylated maize PEPC, consistent with malate inhibiting activity in vivo and compounded by a mismatch in light activation. These results indicate that relieving inhibitory and regulatory constraints, rather than further increasing extractable PEPC capacity, is likely required to increase PEPC-dependent CO2 capture in engineered rice.
Soybean yields are increasingly curtailed by drought; however, the native transcription factor pairs that translate water-deficit signals into a robust antioxidant response have not been fully characterized. Here, we sho...Soybean yields are increasingly curtailed by drought; however, the native transcription factor pairs that translate water-deficit signals into a robust antioxidant response have not been fully characterized. Here, we show that CRISPR/Cas9-mediated knockout of GmWRKY20 reduces antioxidant-enzyme activities and decreases drought tolerance, confirming its essential role in soybean drought tolerance. The bZIP factor GmbZIP9, isolated as a GmWRKY20 interactor, is nuclear-localized and rapidly induced upon dehydration. Overexpression of GmbZIP9 alone elevated reactive oxygen species (ROS) scavenging capacity and enhanced drought tolerance. Critically, co-expression of GmWRKY20 and GmbZIP9 in both yeast and soybean hairy-root assays demonstrated a powerful synergistic effect, conferring superior osmotic-stress tolerance and survival under drought compared with either gene alone. We further identified GmANKTM21, encoding a plasma-membrane ankyrin-repeat protein, as the direct downstream target of this complex. The GmWRKY20-GmbZIP9 heterodimer binds directly to the GmANKTM21 promoter and synergistically drives its transcription, leading to enhanced antioxidant defense. Our findings unveil a key transcriptional regulatory module and provide a rational strategy for pyramiding GmWRKY20 and GmbZIP9 to breed drought-resilient soybean cultivars.
Stress-associated proteins (SAPs), a class of zinc-finger proteins, play crucial roles in plant responses to abiotic stresses, including high temperature; however, their underlying mechanism is largely unknown. Here, we...Stress-associated proteins (SAPs), a class of zinc-finger proteins, play crucial roles in plant responses to abiotic stresses, including high temperature; however, their underlying mechanism is largely unknown. Here, we report that a heat-induced E3 ubiquitin ligase OsSAP3 negatively regulates thermotolerance in rice (Oryza sativa) by specifically interacting with the small heat shock protein OsHSP16. Knockout of OsSAP3 improves seedling survival and maintains grain-setting rates under heat stress. OsSAP3 ubiquitinates the lysine residues K128 and K145 in OsHSP16 to regulate its stability. Unlike OsSAP3, OsHSP16 functions as a positive regulator of thermotolerance in rice, and this enhanced heat resistance correlates with increased antioxidant enzyme activity, reduced reactive oxygen species (ROS) accumulation, decreased relative electrolyte leakage, and upregulation of heat stress defense genes. Genetic interaction analysis supports that OsSAP3 and OsHSP16 operate in the same pathway to modulate heat stress responses, albeit with opposing roles. Furthermore, OsHSP16 binds to and promotes the degradation of putatively misfolded or damaged OsAPX2 (Ascorbate Peroxidase 2) proteins, which may contribute to its role in enhancing thermotolerance in rice. Collectively, our findings reveal a key molecular framework controlling rice heat tolerance and provide a potential gene-editing-based strategy to enhance crop heat resilience.
Stomata are pores in the leaf epidermis that regulate the trade-off between CO2 uptake for photosynthesis and water vapor loss to the atmosphere. Stomatal patterning therefore influences water use efficiency and is a tar...Stomata are pores in the leaf epidermis that regulate the trade-off between CO2 uptake for photosynthesis and water vapor loss to the atmosphere. Stomatal patterning therefore influences water use efficiency and is a target for engineering to avoid drought stress. However, there is limited understanding of how internal leaf anatomy is coordinated with stomatal development, in part due to the technical challenges of assessing three-dimensional anatomy with sufficient resolution. C4 grasses are understudied, and this is a significant knowledge gap given their file-like stomatal distribution and unique mesophyll organization. In this study, wild-type sorghum and a low-stomatal density transgenic line expressing a synthetic Epidermal Patterning Factor (EPFsyn) were studied. High-resolution microCT was paired with machine learning to characterize three-dimensional traits of mesophyll, epidermis, and airspace, which together determine airspace CO2 conductance (gias). Sorghum internal leaf airspace is an arrangement of large sub-stomatal airspaces with thin air passageways. Adaxial and abaxial surfaces differed in stomatal patterning relative to mesophyll structures, sub-stomatal crypts and gias. Adaxial stomata were located above rather than between vascular bundles. Unexpectedly, gias was not significantly different in wild-type versus EPFsyn. EPFsyn plants had larger crypts and shifts in internal leaf anatomy, indicating a potential compensation mechanism for predicted impacts of reduced stomatal density on gias. These findings provide a new understanding of the interplay between leaf surface specific anatomy and internal structural patterning of the mesophyll in a C4 species, and provides knowledge relevant to engineering water use efficiency in crop species.
Axillary bud dormancy is tightly regulated to control shoot branching through an intricate gene regulatory network (GRN). While epigenetic regulation of gene expression plays a key role in modulating GRNs underlying nume...Axillary bud dormancy is tightly regulated to control shoot branching through an intricate gene regulatory network (GRN). While epigenetic regulation of gene expression plays a key role in modulating GRNs underlying numerous developmental and physiological processes, its contribution to axillary bud dormancy remains largely unexplored. Here, we investigate the role of the plant Polycomb Repressive Complex 1 (PRC1) component LIKE HETEROCHROMATIN PROTEIN 1 (LHP1) in lateral shoot branching. Arabidopsis thaliana lhp1 mutants exhibited increased axillary branching, whereas plants overexpressing LHP1 displayed reduced branching compared to wild-type plants. Consistently, the analysis of a transcriptional reporter revealed promoter activity within axillary bud tissues, further indicating that LHP1 plays a role in branch outgrowth repression. Notably, we found that LHP1 directly controls the TCP INTERACTOR CONTAINING EAR MOTIF PROTEIN 1 (TIE1) locus on axillary buds. TIE1 promotes axillary branch development by inhibiting the activity of the master regulator of bud dormancy BRANCHED1 (BRC1). Constitutive expression of TIE1 rescued the reduced-branching phenotype of 35S::LHP1-GFP plants. Moreover, BRC1-direct target loci are induced when LHP1 is overexpressed and severely repressed when TIE1 is artificially expressed avoiding LHP1 control, further indicating that LHP1 acts upstream of TIE1 to induce bud dormancy. Altogether, these results reveal an epigenetic mechanism by which PRC1-mediated repression limits axillary branch development in Arabidopsis.
Kalil A, Tiwari M, Han L
… +13 more, Nagalla S, Li W, Irving T, Binder A, Venkateshwaran M, Maeda J, Delaux PM, Mysore KS, Wen J, Parniske M, Imaizumi-Anraku H, Otegui MS, Ané JM
The nuclear pore complex controls the movement of proteins into and out of the nucleus, allowing cells to regulate protein localization and abundance. This process influences how organisms respond to environmental stimul...The nuclear pore complex controls the movement of proteins into and out of the nucleus, allowing cells to regulate protein localization and abundance. This process influences how organisms respond to environmental stimuli. Components of the nuclear pore complex, including the NUP107-160 sub-complex, NUP133, NUP85, and NENA, are required for root nodulation and arbuscular mycorrhization in Lotus japonicus. However, the specific role of these nucleoporins in symbiotic signaling was poorly understood. Through reverse genetics, we discovered that NUP133 is also required for symbiosis in Medicago truncatula, although the mutant phenotypes were less pronounced than in Lotus. Overexpression of the symbiotic ion channels Medicago DMI1 and Lotus Castor and Pollux in the Lotus Ljnup133, Ljnup85, and Ljnena mutants partially alleviated the nodulation defects. Notably, in NUP107-160 sub-complex mutants of Lotus and Medicago, the accumulation of GFP-labeled Pollux and DMI1 on the inner nuclear membrane was reduced, indicating the NUP107-160 sub-complex plays a key role in regulating the distribution of DMI1 and Pollux on the nuclear envelope. This highlights the extreme sensitivity of nodulation in Lotus to changes in the abundance of Pollux on the inner nuclear membrane. In contrast, Medicago appears to exhibit greater tolerance to alterations in the distribution of DMI1 on the nuclear envelope.
Obligate biotrophic powdery mildew (PM) fungi strictly require living hosts to survive. To search for host factors or processes essential for PM pathogenesis, we conducted a tailored forward genetic screen with the immun...Obligate biotrophic powdery mildew (PM) fungi strictly require living hosts to survive. To search for host factors or processes essential for PM pathogenesis, we conducted a tailored forward genetic screen with the immuno-compromised eds1-2/pad4-1/sid2-2 (eps) triple Arabidopsis mutant. This led to the identification of five allelic disruptive mutations in Mildew Locus O 2 (MLO2) that are responsible for the compromised-immunity-yet-poor infection (cipi) mutant phenotype upon challenge with an adapted PM isolate. Moreover, the eds1/pad4/sid2/mlo2/mlo6/mlo12 (eps3m) sextuple and the eds1/pad4/sid2/pen1/pen2/pen3/mlo2/mlo6/mlo12 (eps3p3m) nonuple mutants displayed near-complete immunity to adapted and non-adapted PM fungi without signs of defense activation, further strengthening the inference that these three clade V MLOs in Arabidopsis may be bona fide host susceptibility factors of PM fungi. Confocal imaging revealed focal accumulation of MLO2-GFP in the peri-penetration peg membranous space, which occurs before and may be required for haustorium differentiation. Ectopic leaf expression analyses of eight other MLOs belonging to different clades showed that only MLO7 can complement the loss of MLO2, MLO6, and MLO12. Results from domain-swapping analyses between MLO1 and MLO2 suggest a bipartite functional configuration for MLO2: its cytoplasmic C-terminus determines where and when MLO2 functions, while its N-terminal seven transmembrane domain-containing region executes the cellular function that is critical for PM pathogenesis. Genetic studies further demonstrated that, unlike MLO7 in synergids, focal accumulation of MLO2 does not depend on FERONIA (FER) and its five paralogs. Together, these findings define clade V MLOs as host factors co-opted by obligate biotrophic PM fungi for successful host colonization.
Soybean serves as a primary global source of high-quality protein and oil, and improving its yield and quality is critical for global food security. Despite advances in gene editing and molecular breeding, the regulatory...Soybean serves as a primary global source of high-quality protein and oil, and improving its yield and quality is critical for global food security. Despite advances in gene editing and molecular breeding, the regulatory mechanisms underlying leaf senescence remain poorly understood, limiting yield gains in soybean. Building on our previous identification of SNAP1/2/3/4-a cluster of NAC transcription factors regulating nodule senescence-we reported their pivotal role in modulating aboveground agronomic traits. The knockout mutants of SNAP1/2/3/4 exhibited delayed leaf senescence and prolonged maturation period. These changes led to concurrent improvements in grain yield, seed size, and oil content. Our study reveals a dual regulatory function of SNAP1/2/3/4 in both nodule and leaf senescence and uncovers a molecular target to coordinately enhance soybean yield and quality by fine-tuning of developmental timing.
Drought stress severely constrains tomato growth and agricultural productivity. Although the core role of the abscisic acid (ABA) signaling pathway in drought response is well-established, the downstream molecular mechan...Drought stress severely constrains tomato growth and agricultural productivity. Although the core role of the abscisic acid (ABA) signaling pathway in drought response is well-established, the downstream molecular mechanisms that directly protect chloroplasts and maintain redox homeostasis remain unclear. This study identifies a chloroplast-localized glutathione peroxidase, SlGPX2, which plays a key role in tomato drought tolerance. SlGPX2-overexpression lines exhibited enhanced drought resistance, reduced stomatal aperture, and lower levels of oxidative damage, whereas knockout lines were more sensitive to drought. Mechanistically, we found that the transcription factor SlAREB directly binds to the SlGPX2 promoter, activating its transcription and thereby linking ABA signaling to downstream antioxidant defense. Furthermore, using multiple experimental approaches, we confirmed that SlGPX2 directly interacts with red chlorophyll catabolite reductase (SlRCCR), a key enzyme in the chlorophyll degradation pathway, forming a functional complex. This interaction is crucial for synergistically maintaining chloroplast structural integrity and reactive oxygen species (ROS) balance under drought stress. Collectively, our findings reveal a SlAREB-SlGPX2-SlRCCR regulatory module that systemically enhances tomato drought tolerance by coordinating stomatal movement with chloroplast antioxidant defense. These results provide a theoretical basis and molecular targets for crop stress-resistance breeding.
MYB transcription factors play crucial roles in orchestrating plant immunity against various pathogens. However, their regulation during virus infection and how viruses counteract these defenses remain poorly understood....MYB transcription factors play crucial roles in orchestrating plant immunity against various pathogens. However, their regulation during virus infection and how viruses counteract these defenses remain poorly understood. In this study, we demonstrated that turnip mosaic virus (TuMV) viral genome-linked protein (VPg) interacts with Nicotiana benthamiana MYB330 (NbMYB330), an R2R3-MYB transcription factor, in the nucleus. NbMYB330 expression was activated at the early stage of TuMV infection, and NbMYB330 positively regulated host antiviral defense. NbMYB330 directly bound to the promoter region of N. benthamiana Catalase1 (NbCAT1), a key gene involved in hydrogen peroxide (H2O2) scavenging, and suppressed its expression to enhance H2O2 accumulation. TuMV VPg targeted NbMYB330 and interfered with its transcriptional repression activity, thus promoting NbCAT1 expression and H2O2 scavenging to enhance virus accumulation. Furthermore, we revealed that potato virus Y (PVY; genus Potyvirus) VPg also targets NbMYB330 to attenuate the H2O2-induced antiviral response. Collectively, our study reveals a previously uncharacterized regulatory module in the plant-potyvirus arms race.
Haploid embryo seed production has been applied to accelerate plant breeding efficiency. Several genes, including DUF679 domain membrane protein (DMP) and phospholipase D3 (PLD3), are involved in maternal haploid inducti...Haploid embryo seed production has been applied to accelerate plant breeding efficiency. Several genes, including DUF679 domain membrane protein (DMP) and phospholipase D3 (PLD3), are involved in maternal haploid induction in maize (Zea mays L.) and other plant species. However, how these gene variants trigger haploid induction and how they functionally interact remain largely unknown. Here, we generated CRISPR-induced DMP-knockout and examined the effects of DMP loss on the lipid composition of pollen and sperm cells in maize. Disruption of DMP led to a pronounced increase in phosphatidic acid (PA) accompanied by a decrease in phosphatidylcholine in sperm cells, with similar but weaker effects in pollen. Consistently, dmp mutants exhibited elevated transcript and protein levels of ZmPLDs, enzymes that hydrolyze phospholipids to produce PA, in both pollen and sperm cells. Immunoblot and PLD activity assays using isolated sperm cell proteins demonstrated the presence of active PLD enzymes in sperm cells and that DMP suppresses PLD activity. Manipulating sperm cell lipid composition further showed that increased PA levels, as well as the addition of DMP, enhance membrane fusogenicity. Structurally, DMP contains an N-terminal intrinsically disordered region and C-terminal transmembrane domains, and the full-length protein is required to suppress PLD activity and to promote membrane fusion. Together, these results indicate that DMP and PA have additive and compensatory effects on membrane fusion, while DMP suppresses PLD expression and PA production. These findings reveal a previously unrecognized role of DMP and its regulatory interplay with PLD in maintaining lipid homeostasis and modulating membrane fusion, providing mechanistic insights into maternal haploid induction.
Fusarium graminearum threatens grain safety through trichothecene mycotoxins, yet how it temporally orchestrates virulence during early root colonization-which compromises seedling vigor and facilitates stem invasion-rem...Fusarium graminearum threatens grain safety through trichothecene mycotoxins, yet how it temporally orchestrates virulence during early root colonization-which compromises seedling vigor and facilitates stem invasion-remains unclear. We performed high-resolution transcriptomics of F. graminearum infecting maize roots every 6 h over 48 hpi, revealing three infection phases: Penetration Initiation (0-6 hpi), Colonization Establishment (12 hpi), and Systemic Disruption (18-48 hpi). Among 6,839 fungal genes, we delineated a three-phase virulence program: rapid activation of protein synthesis enables early secretion of effectors and hydrolases that facilitate host attachment and penetration; sustained deployment of diverse hydrolases and immunosuppressive effectors enables colonization through combined nutrient acquisition and defense suppression; and late-phase vascular degradation coupled with deoxynivalenol (DON) biosynthesis may contribute to systemic host disruption by compromising tissue integrity and disarming immunity. This program coincides with a shift from ROS scavenging to endogenous signaling that may promote toxin production and invasive growth. Notably, we identified FgCPA1, a conserved Phase II carboxypeptidase A essential for root colonization, whose protease domain triggers light-independent cell death in N. benthamiana independent of its signal peptide. This temporal framework uncovers phase-specific coordination of tissue invasion and mycotoxin production, providing actionable targets for anti-virulence strategies to safeguard grain quality.
Argonautes (AGOs) are the effectors for the action of microRNAs (miRNAs). Plant genomes harbor large numbers of AGO genes whose functions remain to be fully understood. Here, we elucidated a function of AGO5 in the ecolo...Argonautes (AGOs) are the effectors for the action of microRNAs (miRNAs). Plant genomes harbor large numbers of AGO genes whose functions remain to be fully understood. Here, we elucidated a function of AGO5 in the ecological model plant Nicotiana attenuata during its interactions with the specialist herbivore Manduca sexta. Plants silenced in NaAGO5 expression using inverted-repeat technology (irAGO5) were indistinguishable from the wild type (WT) in growth and development but were highly susceptible to M. sexta herbivory. M. sexta caterpillars grew faster and accumulated significantly more biomass on irAGO5 than on WT plants. Herbivory-elicited irAGO5 plants accumulated significantly lower amounts of auxin-dependent defense metabolites such as phenolamides, flavonoids, and diterpenoid glycosides, but not nicotine and trypsin protease inhibitors (TPI). Nicotine and TPI levels, which require intact jasmonate signaling, were attenuated in plants silenced in NaAGO8 expression (irAGO8). irAGO5 plants showed compromised herbivore-induced auxin levels and YUCCA gene expression but accumulated more salicylic acid; however, jasmonate accumulations were at WT levels. Exogenous auxin treatments restored resistance against M. sexta and auxin-dependent defense metabolites. Substantial temporal changes in the miRNome were observed in irAGO5 and were largely different from those in irAGO8. An AGO5-dependent miRNA-mRNA regulatory interaction network was inferred for defense-signaling components. Furthermore, double knockdowns of NaAGO5 and NaAGO8 revealed cooperative functions of the two genes during herbivory. We infer that AGO5 is a central component of the herbivore-induced smRNA pathway that modulates multiple nodes in the auxin-dependent metabolic space of the defense signaling network when N. attenuata plants interact with the specialist herbivore M. sexta.
GSM1, a potential DEAH-box RNA helicase, is involved in the glucose-ABA signaling pathway and RNA silencing. Here, MOS2 was identified to interact with GSM1 in the nucleus, and the G-patch domain of MOS2 promoted RNA hel...GSM1, a potential DEAH-box RNA helicase, is involved in the glucose-ABA signaling pathway and RNA silencing. Here, MOS2 was identified to interact with GSM1 in the nucleus, and the G-patch domain of MOS2 promoted RNA helicase activity of GSM1 in vitro. In gsm1-2, reduced levels of several miRNAs and increased levels of their respective target genes were observed. The lack of MOS2 in gsm1-2 (gsm1-2 mos2-3) severely inhibited growth, resulting in seedling lethality and greater reduction of some miRNA levels, implying a genetic interaction between GSM1 and MOS2. HYL1 encodes a double-stranded RNA-binding protein that functions in the DCL1 complex to facilitate pri-miRNA processing. By contrast, gsm1-2 hyl1-2 strongly resembled hyl1-2 in the dwarf phenotype, and the expression levels of several mature miRNAs in gsm1-2 hyl1-2 were comparable to those in hyl1-2, but lower than in gsm1-2. Impaired D-body localization of HYL1 was also observed in gsm1-2, which was detected previously in mos2-2. Moreover, HYL1-pre-miR159a binding affinity was reduced in the presence of GSM1 in vitro. Collectively, these results suggest that GSM1 and MOS2 contribute to miRNA biogenesis, which is largely associated with HYL1-engaged pri-miRNA processing.
Carbon starvation is one of the proposed mechanisms of drought-induced plant mortality. However, it has not been implicated in drought mortality as much as hydraulic failure. We tested the role of carbon on responses to...Carbon starvation is one of the proposed mechanisms of drought-induced plant mortality. However, it has not been implicated in drought mortality as much as hydraulic failure. We tested the role of carbon on responses to drought by limiting stem photosynthesis and increasing tissue non-structural carbohydrates (NSC) in saplings of the tropical tree Calophyllum longifolium Willd. (Calophyllaceae). We first artificially increased [NSC] by exposing half of the saplings to 2000 µmol mol-1 of CO2, while the other half remained at ambient [CO2] for six weeks. Following CO2 treatments, there were no significant differences in predawn leaf water potential (Ψpd), leaf photosynthetic rate, and stem re-assimilation rate between elevated and ambient [CO2] treatments, whereas stem re-assimilation percentage (percentage of dark respiration rate that is re-assimilated) was greater in ambient [CO2]. Exposure to elevated [CO2] produced higher starch and total [NSC] in the tissues of those plants. We then covered the stems of half of the plants from each CO2 treatment to block stem photosynthesis and applied a drought treatment to all plants. Light exclusion reduced stem photosynthesis and most traits responded similarly to drought across the four treatment levels. Drought decreased soluble sugar concentration and increased starch concentration with minimal effects of prior [CO2] treatment. Despite initial differences in starch and total [NSC] between the two [CO2] treatment levels, and physiological responses to light exclusion, leaf and plant mortality occurred at the same pace. Our results demonstrate that stem photosynthesis does not contribute to drought survival in saplings of C. longifolium.