JASMONATE-INSENSITIVE1 encodes a MYC transcription factor essential to discriminate between different jasmonate-regulated defense responses in Arabidopsis

Gibberellin Mediates VvmiR397a-VvLAC4 via VvSLR1-VvWRKY26 Cascade Signal to Repress the Seed-Stone Development During GA-Induced Grape Parthenocarpy

Exogenous gibberellin (GA) effectively inhibits the development of lignified seed-stone in grapes by inducing parthenocarpic seedless berries and significantly improving berry quality. However, the molecular mechanisms underlying this process remain elusive. Here, we uncovered the roles of miR397a in GA signalling-mediated grape seed-stone development through VvSLR1-VvWRKY26 cascade modulation in grapes, indicating 'VvSLR1-VvWRKY26-VvmiR397a-VvLAC4' is the key signalling regulatory module in lignin synthesis of seed-stone in GA-induced grape parthenocarpic berries. VvSLR1 inhibits VvmiR397a expression through interaction with VvWRKY26 and promotes the laccase-mediated lignin synthesis, while GA depresses lignin synthesis by overcoming VvSLR1-mediated multi-level cascade signals. We identified GA responsive cis-element of VvMIR397a promoter bound by VvWRKY26, which activated VvmiR397a expression, whereby inhibiting VvLAC4 level. The expression patterns and cleavage roles' variation of VvmiR397a-VvLAC4 during the seed stones of grape stone-hardening stage indicated that this pair is the one main regulatory module from VvLACs family in this process. Overexpression of VvMIR397a in tobacco and short tandem target mimic (STTM) assays of VvmiR397a/FvmiR397 in grape/strawberry highlighted the function of miR397a-LACs module during modulation of lignin synthesis. Our findings shed novel insights into the GA-responsive roles of VvmiR397a through multi-level cascade signals during modulation of grape seed-stone development, which has important implications for the molecular breeding of high-quality seedless grape berries.

Molecular changes in agroinfiltrated leaves of Nicotiana benthamiana expressing suppressor of silencing P19 and coronavirus-like particles

The production of coronavirus disease 2019 vaccines can be achieved by transient expression of the spike (S) protein of severe acute respiratory syndrome coronavirus 2 in agroinfiltrated leaves of Nicotiana benthamiana. Relying on bacterial vector Agrobacterium tumefaciens, this process is favoured by co-expression of viral silencing suppressor P19. Upon expression, the S protein enters the cell secretory pathway, before being trafficked to the plasma membrane where formation of coronavirus-like particles (CoVLPs) occurs. We previously characterized the effects of influenza virus hemagglutinin forming VLPs through similar processes. However, leaf samples were only collected after 6 days of expression, and it is unknown whether influenza VLPs (HA-VLPs) and CoVLPs induce similar responses. Here, time course sampling was used to profile responses of N. benthamiana leaf cells expressing P19 only, or P19 and the S protein. The latter triggered early but transient activation of the unfolded protein response and waves of transcription factor genes involved in immunity. Accordingly, defence genes were induced with different expression kinetics, including those promoting lignification, terpene biosynthesis, and oxidative stress. Cross-talk between stress hormone pathways also occurred, including repression of jasmonic acid biosynthesis genes after agroinfiltration, and dampening of salicylic acid responses upon S protein accumulation. Overall, HA-VLP- and CoVLP-induced responses broadly overlapped, suggesting nanoparticle production to have the most effects on plant immunity, regardless of the virus surface proteins expressed. Taking advantage of RNAseq inferences, we finally show the co-expression of Kunitz trypsin inhibitors to reduce CoVLP-induced defence and leaf symptoms, with no adverse effect on plant productivity.

Genetic responses of plants to urban environmental challenges

MAIN CONCLUSION

This review aims to describe the main genetic adaptations of plants to abiotic and biotic stressors in urban landscapes through modulation of gene expression and genotypic changes. Urbanization deeply impacts biodiversity through ecosystem alteration and habitat fragmentation, creating novel environmental challenges for plant species. Plants have evolved cellular, molecular, and biochemical strategies to cope with the diverse biotic and abiotic stresses associated with urbanization. However, many of these defense and resistance mechanisms remain poorly understood. Addressing these knowledge gaps is crucial for advancing our understanding of urban biodiversity and elucidating the ecological and evolutionary dynamics of species in urban landscapes. As sessile organisms, plants depend heavily on modifications in gene expression as a rapid and efficient strategy to survive urban stressors. At the same time, the urban environment pressures induced plant species to evolve genotypic adaptations that enhance their survival and growth in these contexts. This review explores the different genetic responses of plants to urbanization. We focus on key abiotic challenges, such as air pollution, elevated CO2 levels, heavy metal contamination, heat and drought stress, salinity, and biotic stresses caused by herbivorous insects. By examining these genetic mechanisms induced by urban stressors, we aim to analyze the molecular pathways and genetic patterns underlying the adaptation of plant species to urban environments. This knowledge is a valuable tool for enhancing the selection and propagation of adaptive traits in plant populations, supporting species conservation efforts, and promoting urban biodiversity.

CeJAZ3 suppresses longifolene accumulation in Casuarina equisetifolia, affecting the host preference of Anoplophora chinensis

BACKGROUND

Casuarina equisetifolia, a crucial species of coastal windbreaks, is highly susceptible to infestation by Anoplophora chinensis. This stem-boring pest poses a significant threat to the health and sustainability of Casuarina equisetifolia forests. Understanding the molecular mechanisms underlying the host preference of A. chinensis to Casuarina equisetifolia is essential for developing effective pest management strategies.

RESULTS

Through field surveys, we identified two cultivars of Casuarina equisetifolia that exhibited differing levels of host preference for A. chinensis. Further analysis of multi-omics data (phenomics, transcriptomics, and metabolomics) from these cultivars revealed that longifolene plays a significant role in attracting A. chinensis to Casuarina equisetifolia. Additionally, the jasmonic acid (JA) signaling pathway was found to suppress longifolene accumulation, primarily through the interaction between the jasmonate ZIM-domain (JAZ) proteins and the terpene synthase (TPS) gene. Moreover, we identified a critical JAZ component, CeJAZ3, whose overexpression led to the down-regulation of TPS expression levels and, consequently, a reduced release of longifolene.

CONCLUSION

We confirmed that the negative regulator of host preference, CeJAZ3, in the JA signaling pathway can suppress the expression of TPSs, thereby down-regulating the accumulation of longifolene in Casuarina equisetifolia and indirectly suppressing the attraction of host plants to A. chinensis, which provides a basis for the integrated management of A. chinensis. © 2024 Society of Chemical Industry.

Isolation and characterization of extracellular polysaccharide from Colletotrichum gloeosporioides: New plant immune elicitor for plant protection

Searching for natural products from microbial sources is an important approach in the development of green pesticides. Here, we isolated a homogenous extracellular polysaccharide CPEPS-2 from Colletotrichum gloeosporioides PHXP3 by bioassay-guided strategy. Chemical and spectroscopic analysis showed that CPEPS-2 consisted of glucose, mannose and galactose in percentages of 38.98:40.04:20.98 and its molecular weight was estimated to be 23.8 kDa. The backbone of CPEPS-2 was consisted of →2)-α-D-Manp-(1→, →6)-α-D-Manp-(1→, →4)-α-D-Glcp-(1→, →2,6)-α-D-Manp-(1→ and →4,6)-α-D-Glcp-(1→ residues, and the branches consisted of β-D-Galf-(1→ unit. In bioactive assays, CPEPS-2 effectively induced systemic resistance of tobacco and soybean against Phytophthora capsici and P. sojae at 100 μg/mL, with inhibition rates of 60.1 % and 68.8 %, respectively. Furthermore, in greenhouse tests, 100 μg/mL CPEPS-2 displayed potent activity against P. capsici and P. sojae with protection efficacies of 75.0 % and 80.4 %. Simultaneously, CPEPS-2 promoted PR1 expression and callose accumulation in Nicotiana benthamiana. In addition, subcellular localization indicated CPEPS-2 was localized to the cell membrane or the wall of plant cells. The results suggested CPEPS-2 could act as a carbohydrate elicitor to induce plant immunity.

Molecular mechanism of response to low-temperature during the natural overwintering period of Rosa persica

KEY MESSAGE

The JA and ICE-CBF-COR signaling pathways play important roles in the low-temperature response of Rosa persica, with RpMYC2 interacting with multiple transcription factors and positively regulating tolerance to low-temperature stress. Rosa persica is highly resilient to cold and drought, making it a valuable resource for breeding in the Rosa. However, the response mechanism of R. persica during the overwintering period remains unclear. This study examined root and stem tissues of R. persica over an eight-month natural open field overwintering period, measuring physiological indices of cold tolerance and investigating changes in cold tolerance across different overwintering stages. The values of physiological indicators of cold hardiness of R. persica roots and stems increased and then decreased. Osmoregulatory substances were the primary contributors to cold hardiness of R. persica roots, while antioxidant enzyme systems played a dominant role in cold hardiness of stems. Differential gene enrichment analyses revealed that oxidative reactions, the synthesis of various secondary metabolites, and hormone signaling pathways are crucial in establishing cold tolerance of R. persica at different overwintering stages. Weighted gene co-expression network and time-ordered gene co-expression network analyses identified the gene RpMYC2 as potentially key to cold tolerance in R. persica. Yeast two-hybrid discovery revealed that RpMYC2 interacts with multiple transcription factors to regulate cold stress resistance in R. persica. Based on the transcriptome, key genes involved in response to low temperature were identified in this study, providing the physiological and molecular insights for cold tolerance breeding of Rosa.

JA and ABA signaling pathways converge to protect plant regeneration in stress conditions

In cuttings, detached leaves or stems are exposed to many stresses during the root regeneration process. Here, we show that the detached Arabidopsis thaliana leaf can tolerate mild osmotic stress and still regenerate roots. Under stress conditions, wounding and stress upregulate the jasmonate (JA) signaling pathway transcription factor gene MYC2 and the abscisic acid (ABA) signaling pathway transcription factor gene ABA INSENSITIVE5 (ABI5). The MYC2-ABI5 complex upregulates the expression of β-GLUCOSIDASE18 (BGLU18), which releases ABA from ABA glucose ester, resulting in ABA accumulation in the detached leaf. Mutations in MYC2, ABI5, and BGLU18 lead to the loss of stress tolerance and defects in root regeneration under osmotic stress. The successive application of JA and ABA can enhance the root regeneration ability in Arabidopsis and poplar cuttings. Overall, the JA-mediated wound signaling pathway and the ABA-mediated stress signaling pathway collaboratively amplify ABA signals to protect root regeneration under stress conditions.

Mechanism Analysis of OsbHLH34-OsERF34 Mediated Regulation of Rice Resistance to Sheath Blight

Transcription factors are pivotal molecules involved in transcriptional and post-transcriptional regulation in plants, playing a crucial role in combating biological stress. Here, we have characterized a regulatory factor, OsbHLH34, which governs the response of rice to infection by Rhizoctonia solani AG1-IA. The expression of OsbHLH34 significantly impacts the susceptibility of rice to Rhizoctonia solani infection. Through the generation of OsbHLH34 knockout and overexpressing rice plants, we observed that OsbHLH34 acts as a positive regulator of rice resistance against rice sheath blight. The average lesion area of overexpression plants was 14.3%, the average lesion area of wildtype plants was 36%, and the average lesion area of mutant plants was 67.6%. Transcriptome and qRT-PCR analysis showed that OsbHLH34 regulates OsERF34, which is a key transcription factor for ethylene biosynthesis and resistance to sheath blight. By employing yeast one-hybrid and dual luciferase assays, we demonstrated that OsbHLH34 directly interacts with the promoter of OsERF34, thereby activating its transcription. Both in vitro and in vivo experiments confirmed OsERF34 as a direct target of OsbHLH34. These findings not only enhance our understanding of the molecular mechanisms underpinning rice disease resistance but also offer novel targets for the improvement of rice disease resistance through breeding strategies.

The MYC Gene RrbHLH105 Contributes to Salt Stress-Induced Geraniol in Rose by Regulating Trehalose-6-Phosphate Signalling

Rose (Rosa rugosa) is an important perfume plant, but its cultivation is significantly constrained by salt stress. Terpenes represent the most abundant volatile aromatic compounds in roses, yet little is known about how terpene metabolism responds to salt stress. In this study, salt-treated rose petals presented significant accumulation of monoterpenes, including geraniol, due to the disruption of jasmonic acid (JA) biosynthesis and signalling. Overexpression and silencing analyses revealed a MYC transcription factor involved in JA signalling (RrbHLH105) as a repressor of geraniol biosynthesis. RrbHLH105 was shown to activate the trehalose-6-phosphate synthase genes RrTPS5 and RrTPS8 by binding to the E-box (5'-CANNTG-3'). The increased trehalose-6-phosphate content and decreased geraniol content in rose petals overexpressing TPS5 or RrTPS8, along with the high accumulation of geraniol in petals where both RrbHLH105 and TPSs were cosilenced, indicate that trehalose signalling plays a role in the negative regulation of geraniol accumulation via the RrbHLH105-TPS module. In summary, the suppression of RrbHLH105 by salt stress leads to excessive geraniol accumulation through the inhibition of both RrbHLH105-mediated JA signalling and RrTPS-mediated trehalose signalling in rose petals. Additionally, this study highlights the emerging role of RrbHLH105 as a critical integrator of JA and trehalose signalling crosstalk.

Phytohormones and emerging plant growth regulators in tailoring plant immunity against viral infections

Viral infections are major contributors to crop yield loss and represent a significant threat to sustainable agriculture. Plants respond to virus attacks by activating sophisticated signalling cascades that initiate multiple defence mechanisms. Notably, several phytohormones, including salicylic acid (SA), jasmonic acid (JA), abscisic acid (ABA), and ethylene (ET), are known to shape these defence responses. In recent years, various plant growth regulators (PGRs) such as melatonin, carrageenans, sulfated fucan oligosaccharides, nitric oxide (NO), brassinosteroids (BRs), and hydrogen sulfide (H2S) have also emerged as crucial regulators of plant defence responses against virus infections. Emerging evidence indicates that these PGRs coordinate with phytohormones to activate various defence strategies, including (1) stomatal closure to limit pathogen entry, (2) callose deposition to block plasmodesmata and restrict viral spread within host tissues, (3) attenuation of viral replication, and (4) activation of RNA interference (RNAi), a crucial antiviral defence response. However, the interactions and crosstalk between PGRs and phytohormones remain largely underexplored, thereby limiting our ability to develop innovative strategies for managing viral diseases. This review discusses the diverse functions and crosstalk among various phytohormones and PGRs in orchestrating the plant defence mechanisms, highlighting their impact on viral replication, movement, and intercellular transport.

Antagonistic systemin receptors integrate the activation and attenuation of systemic wound signaling in tomato

Pattern recognition receptor (PRR)-mediated perception of damage-associated molecular patterns (DAMPs) triggers the first line of inducible defenses in both plants and animals. Compared with animals, plants are sessile and regularly encounter physical damage by biotic and abiotic factors. A longstanding problem concerns how plants achieve a balance between wound defense response and normal growth, avoiding overcommitment to catastrophic defense. Here, we report that two antagonistic systemin receptors, SYR1 and SYR2, of the wound peptide hormone systemin in tomato act in a ligand-concentration-dependent manner to regulate immune homeostasis. Whereas SYR1 acts as a high-affinity receptor to initiate systemin signaling, SYR2 functions as a low-affinity receptor to attenuate systemin signaling. The expression of systemin and SYR2, but not SYR1, is upregulated upon SYR1 activation. Our findings provide a mechanistic explanation for how plants appropriately respond to tissue damage based on PRR-mediated perception of DAMP concentrations and have implications for uncoupling defense-growth trade-offs.

The concerted function of a novel class of transcription factors, ZBFs, in light, jasmonate, and abscisic acid signaling pathways

Several classes of transcription factors have been investigated in light signaling pathways that bind to the light-responsive elements (LREs) present in the promoters of light regulatory genes for transcriptional regulation. Some of these transcription factors have been shown to bind to numerous promoters through genome-wide ChIP-on-chip (ChIP-chip) studies. Furthermore, through the integration of ChIP-seq and RNA-seq techniques, it has been demonstrated that a transcription factor modifies the expression of numerous genes with which it interacts. However, the mode of action of these transcription factors and their dependency on other regulators in the pathway has just started to be unraveled. In this review, we focus on a particular class of transcription factors, ZBFs (Z-box-binding factors), and their associated partners within the same or other classes of transcription factors and regulatory proteins during photomorphogenesis. Moreover, we have further made an attempt to summarize the crosstalk of these transcription factors with jasmonic acid-, abscisic acid-, and salicylic acid-mediated defense signaling pathways. This review offers an in-depth insight into the manner in which ZBFs and their interactors reshape cellular functions and plant behavior. The underlying principles not only contribute to a comprehensive understanding but also establish a framework for analyzing the interplay between early developmental events and hormone signaling, a regulation orchestrated by the ZBF family.

The AMS/DYT1-MYB module interacts with the MED25-MYC-MYB complexes to inhibit jasmonate-regulated floral defense in Arabidopsis

The phytohormone jasmonates (JAs) regulate plant growth and defense responses. The reproductive organs of flowers are devastated by insect herbivores. However, the molecular mechanisms of floral defense remain largely unknown. Here, we found that the Arabidopsis JA receptor CORONATINE INSENSITIVE1 (COI1) and its substrates JA ZIM-domain (JAZ) repressors, and the mediator subunit MEDIATOR25-based MED25-MYC-MYB (MMM) complexes, including MYC2/3/4/5 and MYB28/29/76, mediated floral defense against the insects Helicoverpa armigera, Spodoptera exigua, and Spodoptera frugiperda. The flower-specific IIIa bHLH factors ABORTED MICROSPORES (AMS) and DYSFUNCTIONAL TAPETUM 1 (DYT1) were JAZ-interaction proteins. They interacted with members of the MMM complexes, inhibited the transcriptional activity of MYC2 and MYB28, and repressed floral defense against insects. AMS and DYT1 recruited the flower-specific MYB21/24, and these MYBs interacted with members of MMM complexes, inhibited the MYC2-MYB28 function, and suppressed floral defense against insects. Our study revealed that the JA-COI1-JAZ-MMM pathway mediated flower defense, and the AMS/DYT1-MYB21/24 module antagonized the MMM complexes to repress floral defense against insects.

Unequal Genetic Redundancies Among MYC bHLH Transcription Factors Underlie Seedling Photomorphogenesis in Arabidopsis

Light is one of the most critical ecological cues controlling plant growth and development. Plants have evolved complex mechanisms to cope with fluctuating light signals. In Arabidopsis, bHLH transcription factors MYC2, MYC3, and MYC4 have been shown to play a vital role in protecting plants against herbivory and necrotrophic pathogens. While the role of MYC2 in light-mediated seedling development has been studied in some detail, the role of MYC3 and MYC4 still needs to be discovered. Here, we show that MYC4 negatively regulates seedling photomorphogenesis, while the MYC3 function seems redundant. However, the genetic analysis reveals that MYC3/MYC4 together act as positive regulators of seedling photomorphogenic growth as the myc3myc4 double mutants showed exaggerated hypocotyl growth compared to the myc3 and myc4 single mutants and Col-0. Intriguingly, the loss of MYC2 function in the myc3myc4 double mutant background (myc2myc3myc4) resulted in further enhancement in the hypocotyl growth than myc3myc4 double mutants in WL, BL and FRL, suggesting that MYC2/3/4 together play an essential and positive role in meditating optimal seedling photomorphogenesis. Besides, MYC3/MYC4 genetically and physically interact with HY5 to partially inhibit its function in controlling hypocotyl and photo-pigment accumulation. Moreover, our results suggest that COP1 physically interacts and degrades MYC3 and MYC4 through the 26S proteasomal pathway and controls their response to dark and light for fine-tuning HY5 function and seedling photomorphogenesis.

The role of the jasmonate signalling transcription factors MYC2/3/4 in circadian clock-mediated regulation of immunity in Arabidopsis

Plants are exposed to pathogens at specific, yet predictable times of the day-night cycle. In Arabidopsis, the circadian clock influences temporal differences in susceptibility to the necrotrophic pathogen Botrytis cinerea. The jasmonic acid (JA) pathway regulates immune responses against B. cinerea. The paralogous basic helix-loop-helix transcription factors MYC2, MYC3 and MYC4 are primary regulators of the JA pathway, but their role in regulating temporal variation in immunity is untested. This study aimed to investigate the roles of the MYC transcription factors in the temporal defence response to B. cinerea. We inoculated leaves from wild-type, myc single-, double- and triple-knockout mutants, and lines overexpressing MYC2, MYC3 or MYC4, with B. cinerea at two times of day in constant light, and compared lesion sizes. The presence of MYC2, MYC3 or MYC4 alone was sufficient to maintain temporal variation in susceptibility, but this was abolished in the myc234 triple-knockout mutant. Constitutive expression of MYC2, MYC3 or MYC4 abolished time-of-day differences in susceptibility. The data suggest that MYC2, MYC3 and MYC4 function redundantly in regulating temporal defence responses against B. cinerea and are a point of convergence between the JA pathway and the circadian clock in Arabidopsis.This article is part of the Theo Murphy meeting issue 'Circadian rhythms in infection and immunity'.

A multiprotein regulatory module, MED16-MBR1&2, controls MED25 homeostasis during jasmonate signaling

Mediator25 (MED25) has been ascribed as a signal-processing and -integrating center that controls jasmonate (JA)-induced and MYC2-dependent transcriptional output. A better understanding of the regulation of MED25 stability will undoubtedly advance our knowledge of the precise regulation of JA signaling-related transcriptional output. Here, we report that Arabidopsis MED16 activates JA-responsive gene expression by promoting MED25 stability. Conversely, two homologous E3 ubiquitin ligases, MED25-BINDING RING-H2 PROTEIN1 (MBR1) and MBR2, negatively regulate JA-responsive gene expression by promoting MED25 degradation. MED16 competes with MBR1&2 to bind to the von Willebrand Factor A (vWF-A) domain of MED25, thereby antagonizing the MBR1&2-mediated degradation of MED25 in vivo. In addition, we show that MED16 promotes hormone-induced interactions between MYC2 and MED25, leading to the activation of JA-responsive gene expression. Collectively, our findings reveal a multiprotein regulatory module that robustly and tightly maintains MED25 homeostasis, which determines the strength of the transcriptional output of JA signaling.

Jasmonic acid plays an important role in mediating retrograde signaling under mitochondrial translational stress to balance plant growth and defense

Proper mitochondrial function is crucial to plant growth and development. Inhibition of mitochondrial translation leads to mitochondrial proteotoxic stress, which triggers a protective transcriptional response that regulates nuclear gene expression, commonly referred to as the mitochondrial unfolded protein response (UPRmt). Although the UPRmt has been extensively studied in yeast and mammals, very little is known about the UPRmt in plants. Here, we show that mitochondrial translational stress inhibits plant growth and development by inducing jasmonic acid (JA) biosynthesis and signaling. The inhibitory effect of mitochondrial translational stress on plant growth was alleviated in the JA-signaling-defective mutants coi1-2, myc2, and myc234. Genetic analysis indicated that Arabidopsis mitochondrial ribosomal protein L1 (MRPL1), a key factor in the UPRmt, regulates plant growth in a CORONATINE-INSENSITIVE 1 (COI1)-dependent manner. Moreover, under mitochondrial translational stress, MYC2 shows direct binding to G boxes in the ETHYLENE RESPONSE FACTOR 109 (ERF109) promoter. The induction of ERF109 expression enhances hydrogen peroxide production, which acts as a feedback loop to inhibit root growth. In addition, mutation of MRPL1 increases JA accumulation, reduces plant growth, and enhances biotic stress resistance. Overall, our findings reveal that JA plays an important role in mediating retrograde signaling under mitochondrial translational stress to balance plant growth and defense.

Functional Analysis of Durum Wheat GASA1 Protein as a Biotechnological Alternative Against Plant Fungal Pathogens and a Positive Regulator of Biotic Stress Defense

Plants are frequently challenged by a variety of microorganisms. To protect themselves against harmful invaders, they have evolved highly effective defense mechanisms, including the synthesis of numerous types of antimicrobial peptides (AMPs). Snakins are such compounds, encoded by the GASA (Gibberellic Acid-Stimulated Arabidopsis) gene family, and are involved in the response to biotic and abiotic stress. Here, we examined the function of the newly identified TdGASA1 gene and its encoded protein in Triticum durum subjected to different biotic stress-related simulants, such as mechanical injury, methyl jasmonate (MeJA), indole-3-acetic acid (IAA), salicylic acid (SA), hydrogen peroxide (H2O2), as well as infection with pathogenic fungi Fusarium graminearum and Aspergillus niger. We found that in durum wheat, TdGASA1 transcripts were markedly increased in response to these stress simulants. Isolated and purified TdGASA1 protein exhibited significant antifungal activity in the growth inhibition test conducted on eight species of pathogenic fungi on solid and liquid media. Transgenic Arabidopsis lines overexpressing TdGASA1 obtained in this study showed higher tolerance to detrimental effects of H2O2, MeJA, and ABA treatment. In addition, these lines exhibited resistance to Fusarium graminearum and Aspergillus niger, which was linked to a marked increase in antioxidant activity in the leaves under stress conditions. This resistance was correlated with the upregulation of pathogenesis-related genes (AtPDF1.2a, AtERF1, AtVSP2, AtMYC2, AtPR1, AtACS6, AtETR1, and AtLOX2) in the transgenic lines. Overall, our results indicate that TdGASA1 gene and its encoded protein respond ubiquitously to a range of biotic stimuli and seem to be crucial for the basal resistance of plants against pathogenic fungi. This gene could therefore be a valuable target for genetic engineering to enhance wheat resistance to biotic stress.

VOZ-dependent priming of salicylic acid-dependent defense against Rhizopus stolonifer by β-aminobutyric acid requires the TCP protein TCP2 in peach fruit

Vascular plant one-zinc finger (VOZ) transcription factors (TFs) play crucial roles in plant immunity. Nevertheless, how VOZs modulate defense signaling in response to elicitor-induced resistance is not fully understood. Here, the defense elicitor β-aminobutyric acid (BABA) resulted in the visible suppression of Rhizopus rot disease of peach fruit caused by Rhizopus stolonifer. Defense priming by BABA was notably associated with increased levels of salicylic acid (SA) and SA-dependent gene expression. Data-independent acquisition proteomic analysis revealed that two VOZ proteins (PpVOZ1 and PpVOZ2) were substantially upregulated in BABA-induced resistance (BABA-IR). Furthermore, the interaction of PpVOZ1 and PpVOZ2 and their potential target of the TEOSINTE-BRANCHED1/CYCLOIDEA/PCF (TCP)-family protein PpTCP2 screened from protein-protein interaction networks was confirmed by yeast two-hybrid (Y2H), luciferase complementation imaging and glutathione S-transferase pull-down assays. Furthermore, subcellular localization, yeast one-hybrid, electrophoretic mobility shift assay and dual-luciferase reporter assays demonstrated that nuclear localization of both PpVOZ1 and PpVOZ2 was critical for their contribution to BABA-IR, as these proteins potentiated the PpTCP2-mediated transcriptional activation of isochorismate synthase genes (ICS1/2). The overexpression of both PpVOZ1 and PpVOZ2 could activate the transcription of SA-dependent genes and provide disease resistance in transgenic Arabidopsis. In contrast, the ppvoz1cas9 and ppvoz2cas9 loss-of-function mutations and the voz1cas9 voz2cas9 double mutation attenuated BABA-IR against R. stolonifer. Therefore, the three identified positive TFs, PpVOZ1, PpVOZ2, and PpTCP2, synergistically contribute to the BABA-activated priming of systemic acquired resistance in postharvest peach fruit by a VOZ-TCP-ICS regulatory module.

Jasmonate induces translation of the Arabidopsis transfer RNA-binding protein YUELAO1, which activates MYC2 in jasmonate signaling

Jasmonate is ubiquitous in the plant kingdom and regulates multiple physiological processes. Although jasmonate signaling has been thoroughly investigated in Arabidopsis thaliana, most studies have focused on the transcriptional mechanisms underlying various jasmonate responses. It remains unclear whether (and how) translation-related pathways help improve transcription efficiency to modulate jasmonate signaling, which may enable plants to respond to stressful conditions effectively. Here, we demonstrate that jasmonate induces translation of the transfer RNA (tRNA)-binding protein YUELAO 1 (YL1) via a specific region in its 3' untranslated region (3' UTR). YL1 and its homolog YL2 redundantly stimulate jasmonate responses such as anthocyanin accumulation and root growth inhibition, with the YL1 3' UTR being critical for YL1-promoted jasmonate responses. Once translated, YL1 acts as an activator of the MYC2 transcription factor through direct interaction, and disrupting YL1 3' UTR impairs the YL1-mediated transcriptional activation of MYC2. YL1 enhances jasmonate responses mainly in a MYC2-dependent manner. Together, these findings reveal a translational mechanism involved in jasmonate signaling and advance our understanding of the transcriptional regulation of jasmonate signaling. The YL1 3' UTR acts as a crucial signal transducer that integrates translational and transcriptional regulation, allowing plants to respond to jasmonate in a timely fashion.

Unveiling the wheat-rust battleground: A transcriptomic journey

The global wheat production faces significant challenges due to major rust-causing fungi, namely Puccinia striiformis f. sp. tritici, P. triticina, and P. graminis f. sp. tritici, responsible for stripe, leaf, and stem rust diseases, respectively. The evolutionary relationship between wheat (host) and Puccinia (pathogen) renders existing wheat resistance ineffective over time. The most viable solution to this issue lies in the development of new resistant wheat varieties. However, achieving this requires a comprehensive understanding of wheat's defense mechanisms against ever-evolving pathogens. Transcriptomics emerges as a powerful tool for analyzing gene activity at the molecular level. Over the last decade, this technique has transformed our comprehension of the wheat-rust interaction. Transcriptomics has unveiled a compelling "biphasic model" of gene expression in wheat infected with rust fungi, delineating two distinct phases of defense activation. Moreover, it has illuminated the intricate signaling pathways, hormonal interactions, and diverse defense mechanisms employed by wheat. These mechanisms encompass the oxidative burst, reinforcement of cell walls, and controlled cessation of photosynthesis, all aimed at combatting the invading pathogen. However, the utility of transcriptomics extends beyond elucidating defense strategies; it enables the identification of novel genes linked to resistance or susceptibility. By unraveling the functions of these genes, researchers can uncover new avenues for breeding resistant wheat varieties, arming wheat with the molecular arsenal necessary to prevail in the ongoing battle against rust fungi. This review represents a pioneering effort in exploring transcriptomic techniques and accumulated data to present a comprehensive overview of the wheat-Puccinia interaction at the system-wide level.

High-throughput capture of transcription factor-driven epigenome dynamics using PHILO ChIP-seq

Assessing the dynamics of chromatin features and transcription factor (TF) binding at scale remains a significant challenge in plants. Here, we present PHILO (Plant HIgh-throughput LOw input) ChIP-seq, a high-throughput ChIP-seq platform that enables the cost-effective and extensive capture of TF binding and genome-wide distributions of histone modifications. The PHILO ChIP-seq pipeline is adaptable to many plant species, requires very little starting material (1mg), and provides the option to use MNase (micrococcal nuclease) for chromatin fragmentation. By employing H3K9ac PHILO ChIP-seq on eight Arabidopsis thaliana jasmonic acid (JA) pathway mutants, with the simultaneous processing of over 100 samples, we not only recapitulated but also expanded the current understanding of the intricate interplay between the master TFs MYC2/3/4 and various chromatin regulators. Additionally, our analyses brought to light previously unknown histone acetylation patterns within the regulatory regions of MYC2 target genes in Arabidopsis, which is also conserved in tomato (Solanum lycopersicum). In summary, our PHILO ChIP-seq platform demonstrates its high effectiveness in investigating TF binding and chromatin dynamics on a large scale in plants, paving the way for the cost-efficient realization of complex experimental setups.

SmJAZ1/8 inhibits the stimulation of SmbHLH59, which limits the accumulation of salvianolic acids and tanshinones in Salvia miltiorrhiza

Salvia miltiorrhiza is a model medicinal plant that is typically used to treat cardiovascular and cerebrovascular diseases. The primary active medicinal ingredients of S. miltiorrhiza are salvianolic acids and tanshinones. Jasmonate (JA) is a vital phytohormone that regulates secondary metabolism. The exogenous application of methyl jasmonate (MeJA) can promote the accumulation of active ingredients in S. miltiorrhiza. Here, we identified a MeJA-responsive SmbHLH59 gene that encodes for a bHLH IIIe family transcription factor. The overexpression of SmbHLH59 in S. miltiorrhiza increased the contents of salvianolic acids and tanshinones, while the opposite effect was observed when SmbHLH59 was knocked out via CRISPR. Meanwhile, SmbHLH59 was observed to activate the expressions of SmPAL1, SmC4H1, SmHPPR1, SmCPS1, and SmKSL1 genes by binding to the E/G-box elements of their promoters. Further investigations demonstrated that SmJAZ1 and SmJAZ8 interacted with SmbHLH59 to inhibit its activation of these five genes. In summary, a JA signaling pathway component (SmbHLH59) was identified that strongly enhanced the accumulation of salvianolic acids and tanshinones through the direct activation of multiple enzyme genes in their biosynthetic pathways. Consequently, this study enriches our knowledge toward further elucidating the molecular mechanisms behind the regulation of JA in the secondary metabolism of S. miltiorrhiza.

Genome-wide identification of the eggplant jasmonate ZIM-domain (JAZ) gene family and functional characterization of SmJAZ10 in modulating chlorophyll synthesis in leaves

The jasmonate ZIM-domain (JAZ) plays a crucial role in regulating several economic traits in crops. Despite its importance, the characterization of the SmJAZ gene family in eggplant (Solanum melongena L.) has not been documented. In this study, we identified 13 SmJAZ distributed across 9 chromosomes, which were categorized into 5 subgroups based on phylogenetic analysis. Both of them possess TIFY-motif and CCT_2 domains with varying degrees of variation. Promoter cis-element analysis predicted 42 distributed cis-elements that respond to diverse signals. Gene expression analysis demonstrated that SmJAZ exhibited responsiveness to JA, ABA, NaCl, PEG, 4 °C, blue light, and UV-B treatments. Moreover, microRNA interaction predictions identified 150 potential miRNAs, among which ath-miR5021 was found to target 8 SmJAZ mRNAs. Yeast two-hybrid assays demonstrated that most of the SmJAZs were able to interact with SmMYC2 and SmNINJA and could form JAZ-JAZ complexes. Subcellular localization analysis unveiled a diverse array of intranuclear and extranuclear localization signals for SmJAZs. Overexpressing of SmJAZ10 could decrease the chlorophyll content of seedling leaves, and the transcriptome showed that genes related to chlorophyll synthesis, such as SmCHLH, SmPORA, and SmGLK2, underwent down-regulated expression. Overall, these findings serve as a valuable resource for leveraging JA signaling to enhance eggplant quality.

bHLH19 and bHLH20 repress jasmonate-mediated plant defense against insect herbivores in Arabidopsis

Plants are attacked by various insect herbivores. Upon attack-triggered biosynthesis of the phytohormone jasmonates (JAs), the JA receptor CORONATINE INSENSITIVE 1 recruits the JA-ZIM domain (JAZ) repressors for ubiquitination, releases the MYC-MYB transcription factor (TF) complexes, and enhances glucosinolates (GSs) biosynthesis to promote defense against insects in Arabidopsis. However, the negative regulation of JA-regulated defense remains largely unclear. Here, we found that Arabidopsis IVa bHLH TFs bHLH19 and bHLH20 interacted with JAZs. The bhlh19/20 mutations enhanced defense against the insects Spodoptera frugiperda and S. exigua, while their overexpression inhibited defense. bHLH19/20 repressed defense via at least two layers of regulation: first, bHLH19/20 interacted with the members MYC2/3/4/5 and MYB34/51/122 of MYC-MYB complexes, and inhibited the interaction/transcription activity of MYC2-MYB34; second, bHLH19/20 activated the RNA level of nitrile-specifier protein 1, which converts GSs into the less toxic nitriles. bhlh19/20 exhibited no penalty in JA-regulated growth inhibition. Collectively, our findings reveal the molecular mechanism for negatively regulating JA-mediated defense against insects in Arabidopsis without growth penalty by the pair of bHLH19/20 TFs.

CRISPR/Cas9-mediated knockout of NtMYC2a gene involved in resistance to bacterial wilt in tobacco

MYC2 is a class of bHLH family transcription factors and a major regulatory factor in the JA signaling pathway, and its molecular function in tobacco has not been reported. In this study, CRISPR/Cas9-mediated MYC2 gene NtMYC2a knockout mutants at tobacco was obtained and its agronomic traits, disease resistance, and chemical composition were identified. Comparing with the WT, the leaf width of the KO-NtMYC2a was narrowed, the nornicotine content and mecamylamine content increased significantly and the resistance to Ralstonia solanacearum significantly decreased. The transcriptome sequencing results showed that DEGs related to immunity, signal transduction and growth and development were enriched between KO-NtMYC2a and WT. NtJAR1 and NtCOI1 in KO-NtMYC2a were down-regulated to regulating the JA signaling pathway, result in a significant decrease in tobacco's resistance to R. solanacearum. Our research provides theoretical support for the functional research of MYC2 and the study of the mechanism of tobacco bacterial wilt resistance.

Transcription factor ABF3 modulates salinity stress-enhanced jasmonate signaling in Arabidopsis

Salinity is a severe abiotic stress that affects plant growth and yield. Salinity stress activates jasmonate (JA) signaling in Arabidopsis thaliana, but the underlying molecular mechanism remains to be elucidated. In this study, we confirmed the activation of JA signaling under saline conditions and demonstrated the importance of the CORONATINE INSENSITIVE1 (COI1)-mediated JA signaling for this process. Phenotypic analyses reflected the negative regulation of JASMONATE ZIM-DOMAIN (JAZ) repressors during salinity stress-enhanced JA signaling. Mechanistic analyses revealed that JAZ proteins physically interact with ABSCISIC ACID-RESPONSIVE ELEMENT BINDING FACTOR1 (ABF1), AREB1/ABF2, ABF3, and AREB2/ABF4, which belong to the basic leucine zipper (bZIP) transcription factor family and respond to salinity stress. Analyses on the ABF3 overexpression plants and ABF mutants indicated the positive role of ABF3 in regulating JA signaling under saline condition. Furthermore, ABF3 overexpression partially recovered the JA-related phenotypes of JAZ1-Δ3A plants. Moreover, ABF3 was observed to indirectly activate ALLENE OXIDE SYNTHASE (AOS) transcription, but this activation was inhibited by JAZ1. In addition, ABF3 competitively bind to JAZ1, thereby decreasing the interaction between JAZ1 and MYC2, which is the master transcription factor controlling JA signaling. Collectively, our findings have clarified the regulatory effects of ABF3 on JA signaling and provide new insights into how JA signaling is enhanced following an exposure to salinity stress.

The MYC transcription factor PbrMYC8 negatively regulates PbrMSL5 expression to promote pollen germination in Pyrus

The successful germination of pollen is essential for double fertilization in flowering plants. Mechanosensitive channels of small conductance (MscS-like, MSL) inhibit pollen germination and maintains cellular integrity of pollen during this process. Therefore, it is vital to carefully regulate the expression of MSL to promote successful pollen germination. Despite its importance, the molecular mechanisms governing MSL expression in plants remain poorly understood. Here, we had identified 15 MSL genes in the pear, among which PbrMSL5 was expressed in pollen development. Subcellular localization experiments revealed that PbrMSL5 was located in both plasma membrane and cytoplasm. Functional investigations, including complementation experiments using the atmsl8 mutant background, demonstrated the involvement of PbrMSL5 in preserving pollen cell integrity and inhibiting germination. Antisense oligonucleotide experiments further confirmed that PbrMSL5 suppressed pear pollen germination by reducing osmotic pressure and Cl- content. Yeast one-hybrid, electrophoretic mobility shift assays, and dual luciferase reporter assay elucidated that PbrMYC8 interacts directly with the N-box element, leading to the suppression of PbrMSL5 expression and promoted pollen germination. These results represented a significant advancement in unraveling the molecular mechanisms controlling plant MSL expression. This study showed valuable contribution to advancing our comprehension of the mechanism underlying pollen germination.

The Arabidopsis ARID-HMG DNA-BINDING PROTEIN 15 modulates jasmonic acid signaling by regulating MYC2 during pollen development

The intricate process of male gametophyte development in flowering plants is regulated by jasmonic acid (JA) signaling. JA signaling initiates with the activation of the basic helix-loop-helix transcription factor (TF), MYC2, leading to the expression of numerous JA-responsive genes during stamen development and pollen maturation. However, the regulation of JA signaling during different stages of male gametophyte development remains less understood. This study focuses on the characterization of the plant ARID-HMG DNA-BINDING PROTEIN 15 (AtHMGB15) and its role in pollen development in Arabidopsis (Arabidopsis thaliana). Phenotypic characterization of a T-DNA insertion line (athmgb15-4) revealed delayed bolting, shorter siliques, and reduced seed set in mutant plants compared to the wild type. Additionally, AtHMGB15 deletion resulted in defective pollen morphology, delayed pollen germination, aberrant pollen tube growth, and a higher percentage of nonviable pollen grains. Molecular analysis indicated the downregulation of JA biosynthesis and signaling genes in the athmgb15-4 mutant. Quantitative analysis demonstrated that JA and its derivatives were ∼10-fold lower in athmgb15-4 flowers. Exogenous application of methyl jasmonate could restore pollen morphology and germination, suggesting that the low JA content in athmgb15-4 impaired JA signaling during pollen development. Furthermore, our study revealed that AtHMGB15 physically interacts with MYC2 to form a transcription activation complex. This complex promotes the transcription of key JA signaling genes, the R2R3-MYB TFs MYB21 and MYB24, during stamen and pollen development. Collectively, our findings highlight the role of AtHMGB15 as a positive regulator of the JA pathway, controlling the spatiotemporal expression of key regulators involved in Arabidopsis stamen and pollen development.

Biosynthesis and Signaling of Strigolactones Act Synergistically With That of ABA and JA to Enhance Verticillium dahliae Resistance in Cotton (Gossypium hirsutum L.)

Verticillium wilt (VW) caused by the soil-borne fungal pathogen Verticillium dahliae reduces cotton productivity and quality. Numerous studies have explored the genetic and molecular mechanisms regulating VW resistance in cotton, but the role and mechanism of strigolactone (SL) is still elusive. We investigated the function of SL in cotton's immune response to V. dahliae infection by exogenously applying SL analog, blocking or enhancing biosynthesis of endogenous SLs in combination with comparative transcriptome analysis and by exploring cross-talk between SL and other phytohormones. Silencing GhDWARF27 and applying the SL analog GR24 or overexpressing GhDWARF27 decreased and enhanced V. dahliae resistance, respectively. Transcriptome analysis revealed SL-mediated activation of abscisic acid (ABA) and jasmonic acid (JA) biosynthesis and signaling pathways. Enhanced ABA biosynthesis and signaling led to increased activity of antioxidant enzymes and reduced buildup of excess reactive oxygen species. Enhanced JA biosynthesis and signaling facilitated transcription of JA-dependent disease resistance genes. One of the components of the SL signal transduction pathway, GhD53, was found to interact with GhNCED5 and GhLOX2, the key enzymes of ABA and JA biosynthesis, respectively. We revealed the molecular mechanism underlying SL-enabled V. dahliae resistance and provided potential solutions for improving VW resistance in cotton.

Multiomic analyses reveal key sectors of jasmonate-mediated defense responses in rice

The phytohormone jasmonate (JA) plays a central role in plant defenses against biotic stressors. However, our knowledge of the JA signaling pathway in rice (Oryza sativa) remains incomplete. Here, we integrated multiomic data from three tissues to characterize the functional modules involved in organizing JA-responsive genes. In the core regulatory sector, MYC2 transcription factor transcriptional cascades are conserved in different species but with distinct regulators (e.g. bHLH6 in rice), in which genes are early expressed across all tissues. In the feedback sector, MYC2 also regulates the expression of JA repressor and catabolic genes, providing negative feedback that truncates the duration of JA responses. For example, the MYC2-regulated NAC (NAM, ATAF1/2, and CUC2) transcription factor genes NAC1, NAC3, and NAC4 encode proteins that repress JA signaling and herbivore resistance. In the tissue-specific sector, many late-expressed genes are associated with the biosynthesis of specialized metabolites that mediate particular defensive functions. For example, the terpene synthase gene TPS35 is specifically induced in the leaf sheath and TPS35 functions in defense against oviposition by brown planthoppers and the attraction of this herbivore's natural enemies. Thus, by characterizing core, tissue-specific, and feedback sectors of JA-elicited defense responses, this work provides a valuable resource for future discoveries of key JA components in this important crop.

The wheat pathogenesis-related protein (TdPR1.2) enhanced tolerance to abiotic and biotic stresses in transgenic Arabidopsis plants

In plants, the pathogenesis-related (PR) proteins have been identified as important regulators of biotic and abiotic stresses. PR proteins branch out into 19 different classes (PR1-PR19). Basically, all PR proteins display a well-established method of action, with the notable exception of PR1, which is a member of a large superfamily of proteins with a common CAP domain. We have previously isolated and characterized the first PR1 from durum wheat, called TdPR-1.2. In the current research work, TdPR1.2 gene was used to highlight its functional activities under various abiotic (sodium chloride (100 mM NaCl) and oxidative stresses (3 mM H2O2), hormonal salicylic acid (SA), abscisic acid (ABA) and jasmonic acid (JA), and abiotic stresses (Botrytis cinerea and Alternaria solani). Enhancement survival index was detected in Arabidopsis transgenic plants expressing TdPR1.2 gene. Moreover, quantitative real-time reverse transcription PCR (qRT-PCR) analysis demonstrated induction of antioxidant enzymes such as catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD). It equally revealed a decrease of malondialdehyde (MDA) as well as hydrogen peroxide (H2O2) levels in transgenic Arabidopsis plants compared to control lines, confirming the role of TdPR1.2 in terms of alleviating biotic and abiotic stresses in transgenic Arabidopsis plants. Eventually, RT-qPCR results showed a higher expression of biotic stress-related genes (PR1 and PDF1.2) in addition to a downregulation of the wound-related gene (LOX3 and VSP2) in transgenic lines treated with jasmonic acid (JA). Notably, these findings provide evidence for the outstanding functions of PR1.2 from durum wheat which can be further invested to boost tolerance in crop plants to abiotic and biotic stresses.

A bHLH transcription factor AaMYC2-type positively regulates glandular trichome density and artemisinin biosynthesis in Artemisia annua

Artemisinin-based combinational therapies (ACTs) constitute the first line of malaria treatment. However, due to its trichome-specific biosynthesis, low concentration, and poor understanding of regulatory mechanisms involved in artemisinin biosynthesis and trichome development, it becomes very difficult to meet the increased demand for ACTs. Here, we have reported that a bHLH transcription factor, AaMYC2-type, plays an important role in regulating GST development and artemisinin biosynthesis in Artemisia annua. AaMYC2-type encodes a protein that is transcriptionally active and localised to the nucleus. It is prominently expressed in aerial parts like leaves, stems, inflorescence and least expressed in roots. AaMYC2-type expression is significantly increased under different hormonal treatments. In transgenic overexpression lines, AaMYC2-type OE, a significant increase in the expression of trichome development and artemisinin biosynthesis genes was observed. While in knockdown lines, Aamyc2-type, expression of trichome development and artemisinin biosynthesis genes were significantly reduced. Yeast one-hybrid assay clearly shows that the AaMYC2-type directly binds to the E-boxes in the promoter regions of ADS and CYP71AVI. The SEM microscopy depicted the number of trichomes elevated from 11 mm-2 in AaMYC2-type OE lines to 6.1 mm-2 in Aamyc2-type. The final effect of the alteration in biosynthetic and trichome developmental genes was observed in the accumulation of artemisinin. In the AaMYC2-type OE, the artemisinin content was 12 mg g-1DW, which was reduced to 3.2 mg g-1DW in the Aamyc2-type. Altogether, the above findings suggest that the AaMYC2-type play a dual regulating role in controlling both trichome developmental and artemisinin biosynthetic genes.

Jasmonate-insensitive mutant jar1b prevents petal elongation and flower opening coupling with parthenocarpic fruit development in Cucurbita pepo

Jasmonates are growth regulators that play a key role in flower development, fruit ripening, root growth, and plant defence. The study explores the coordination of floral organ maturation to ensure proper flower opening for pollination and fertilization. A new mutant (jar1b) was discovered, lacking petal elongation and flower opening but showing normal pistil and stamen development, leading to parthenocarpic fruit development. The mutation also enhanced the elongation of roots while reducing the formation of root hairs. BSA sequencing showed that jar1b is a missense mutation in the gene CpJAR1B, which encodes the enzyme that catalyzes the conjugation between JA and the amino acid isoleucine. The loss of function mutation in CpJAR1B produced a deficiency in biologically active (+) -7-iso-jasmonoyl-L-isoleucine (JA-Ile), which was not complemented by the paralogous gene CpJAR1A or any other redundant gene. Exogenous application of methyl jasmonate (MeJA) demonstrated that jar1b is partially insensitive to JA in both flowers and roots. Further experimentation involving the combination of JA-Ile deficient and ethylene-deficient, and ET insensitive mutations in double mutants revealed that CpJAR1B mediated ET action in female petal maturation and flower opening, but JA and ET have independent additive effects as negative regulators of the set and development of squash fruits. CpJAR1B also regulated the aperture of male flowers in an ethylene-independent manner. The root phenotype of jar1b and effects of external MeJA treatments indicated that CpJAR1B has a dual role in root development, inhibiting the elongation of primary and secondary roots, but promoting the formation of root hairs.

Identification of the sweet orange (Citrus sinensis) bHLH gene family and the role of CsbHLH55 and CsbHLH87 in regulating salt stress

Salt stress is one of the primary environmental stresses limiting plant growth and production and adversely affecting the growth, development, yield, and fruit quality of Citrus sinensis. bHLH (basic helix-loop-helix) genes are involved in many bioregulatory processes in plants, including growth and development, phytohormone signaling, defense responses, and biosynthesis of specific metabolites. In this study, by bioinformatics methods, 120 CsbHLHgenes were identified, and phylogenetic analysis classified them into 18 subfamilies that were unevenly distributed on nine chromosomes. The cis-acting elements of the CsbHLH genes were mainly hormone-related cis-acting elements. Seventeen CsbHLH genes exhibited significant differences in expression under salt stress. Six CsbHLH genes with significant differences in expression were randomly selected for quantitative real-time polymerase chain reaction (qRT-PCR) validation. The qRT-PCR results showed a strong correlation with the transcriptome data. Phytohormones such as jasmonic acid (JA) are essential for biotic and abiotic stress responses in plants, and CsbHLH55 and CsbHLH87 are considered candidate target genes for sweet orange MYC2 transcription factors involved in the JA signaling pathway. These genes are the main downstream effectors in the JA signaling pathway and can be activated to participate in the JA signaling pathway. Activation of the JA signaling pathway inhibits the production of reactive oxygen species and improves the salt tolerance of sweet orange plants. The CsbHLH55 and CsbHLH87 genes could be candidate genes for breeding new transgenic salt-resistant varieties of sweet orange.

The complex relationship between disease resistance and yield in crops

In plants, growth and defence are controlled by many molecular pathways that are antagonistic to one another. This results in a 'growth-defence trade-off', where plants temporarily reduce growth in response to pests or diseases. Due to this antagonism, genetic variants that improve resistance often reduce growth and vice versa. Therefore, in natural populations, the most disease resistant individuals are often the slowest growing. In crops, slow growth may translate into a yield penalty, but resistance is essential for protecting yield in the presence of disease. Therefore, plant breeders must balance these traits to ensure optimal yield potential and yield stability. In crops, both qualitative and quantitative disease resistance are often linked with genetic variants that cause yield penalties, but this is not always the case. Furthermore, both crop yield and disease resistance are complex traits influenced by many aspects of the plant's physiology, morphology and environment, and the relationship between the molecular growth-defence trade-off and disease resistance-yield antagonism is not well-understood. In this article, we highlight research from the last 2 years on the molecular mechanistic basis of the antagonism between defence and growth. We then discuss the interaction between disease resistance and crop yield from a breeding perspective, outlining the complexity and nuances of this relationship and where research can aid practical methods for simultaneous improvement of yield potential and disease resistance.

Crosstalk between Ethylene, Jasmonate and ABA in Response to Salt Stress during Germination and Early Plant Growth in Cucurbita pepo

The crosstalk of phytohormones in the regulation of growth and development and the response of plants to environmental stresses is a cutting-edge research topic, especially in crop species. In this paper, we study the role and crosstalk between abscisic acid (ABA), ethylene (ET), and jasmonate (JA) in the control of germination and seedling growth in water or in standard nutrient solution and under salt stress (supplemented with 100-200 mM NaCl). The roles of ET and JA were studied using squash ET- and JA-deficient mutants aco1a and lox3a, respectively, while the crosstalk between ET, JA, and ABA was determined by comparing the expression of the key ABA, JA, and ET genes in wild-type (WT) and mutant genotypes under standard conditions and salt stress. Data showed that ET and JA are positive regulators of squash germination, a function that was found to be mediated by downregulating the ABA biosynthesis and signaling pathways. Under salt stress, aco1a germinated earlier than WT, while lox3a showed the same germination rate as WT, indicating that ET, but not JA, restricts squash germination under unfavorable salinity conditions, a function that was also mediated by upregulation of ABA. ET and JA were found to be negative regulators of plant growth during seedling establishment, although ET inhibits both the aerial part and the root, while JA inhibits only the root. Both aco1a and lox3a mutant roots showed increased tolerance to salt stress, a phenotype that was found to be mainly mediated by JA, although we cannot exclude that it is also mediated by ABA.

Advances in functional studies of plant MYC transcription factors

Myelocytomatosis (MYC) transcription factors (TFs) belong to the basic helix-loop-helix (bHLH) family in plants and play a central role in governing a wide range of physiological processes. These processes encompass plant growth, development, adaptation to biotic and abiotic stresses, as well as secondary metabolism. In recent decades, significant strides have been made in comprehending the multifaceted regulatory functions of MYCs. This advancement has been achieved through the cloning of MYCs and the characterization of plants with MYC deficiencies or overexpression, employing comprehensive genome-wide 'omics' and protein-protein interaction technologies. MYCs act as pivotal components in integrating signals from various phytohormones' transcriptional regulators to orchestrate genome-wide transcriptional reprogramming. In this review, we have compiled current research on the role of MYCs as molecular switches that modulate signal transduction pathways mediated by phytohormones and phytochromes. This comprehensive overview allows us to address lingering questions regarding the interplay of signals in response to environmental cues and developmental shift. It also sheds light on the potential implications for enhancing plant resistance to diverse biotic and abiotic stresses through genetic improvements achieved by plant breeding and synthetic biology efforts.

OPDA/dn-OPDA actions: biosynthesis, metabolism, and signaling

Plants cannot move, so they have evolved sophisticated strategies that integrate the external environmental cues and internal signaling networks for adaptation to dynamic circumstances. Cis-(+)-12-oxo-phytodienoic acid (OPDA) and 2,3-dinor-OPDA (dn-OPDA), the cyclopentenone-containing oxylipins, ubiquitously occur in the green lineage to orchestrate a series of growth and developmental processes as well as various stress and defense responses. OPDA/dn-OPDA are precursors of jasmonate (JA) biosynthesis in vascular plants. Dn-OPDA and its isomer also serve as bioactive JAs perceived by the coronatine insensitive 1/jasmonate ZIM-domain (COI1/JAZ) co-receptor complex in bryophytes and lycophytes. In addition, OPDA/dn-OPDA display signaling activities independent of (+)-7-iso-jasmonoyl-L-isoleucine (JA-Ile) and COI1 in both vascular and non-vascular plants. In this review, we discuss recent advances in the biosynthesis, metabolism, and signaling of OPDA/dn-OPDA, and provide an overview of the evolution of OPDA/dn-OPDA actions to obtain a deeper understanding of the pervasive role of OPDA/dn-OPDA in the plant life cycle.

A structure-redesigned intrinsically disordered peptide that selectively inhibits a plant transcription factor in jasmonate signaling

Plant hormone-related transcription factors (TFs) are key regulators of plant development, responses to environmental stress such as climate changes, pathogens, and pests. These TFs often function as families that exhibit genetic redundancy in higher plants, and are affected by complex crosstalk mechanisms between different plant hormones. These properties make it difficult to analyze and control them in many cases. In this study, we introduced a chemical inhibitor to manipulate plant hormone-related TFs, focusing on the jasmonate (JA) and ethylene (ET) signaling pathways, with the key TFs MYC2/3/4 and EIN3/EIL1. This study revealed that JAZ10CMID, the binding domain of the repressor involved in the desensitization of both TFs, is an intrinsically disordered region in the absence of binding partners. Chemical inhibitors have been designed based on this interaction to selectively inhibit MYC TFs while leaving EIN3/EIL1 unaffected. This peptide inhibitor effectively disrupts MYC-mediated responses while activating EIN3-mediated responses and successfully uncouples the crosstalk between JA and ET signaling in Arabidopsis thaliana. Furthermore, the designed peptide inhibitor was also shown to selectively inhibit the activity of MpMYC, an ortholog of AtMYC in Marchantia polymorpha, demonstrating its applicability across different plant species. This underscores the potential of using peptide inhibitors for specific TFs to elucidate hormone crosstalk mechanisms in non-model plants without genetic manipulation. Such a design concept for chemical fixation of the disordered structure is expected to limit the original multiple binding partners and provide useful chemical tools in chemical biology research.

Redox Regulation by Priming Agents Toward a Sustainable Agriculture

Plants are sessile organisms that are often subjected to a multitude of environmental stresses, with the occurrence of these events being further intensified by global climate change. Crop species therefore require specific adaptations to tolerate climatic variability for sustainable food production. Plant stress results in excess accumulation of reactive oxygen species leading to oxidative stress and loss of cellular redox balance in the plant cells. Moreover, enhancement of cellular oxidation as well as oxidative signals has been recently recognized as crucial players in plant growth regulation under stress conditions. Multiple roles of redox regulation in crop production have been well documented, and major emphasis has focused on key redox-regulated proteins and non-protein molecules, such as NAD(P)H, glutathione, peroxiredoxins, glutaredoxins, ascorbate, thioredoxins and reduced ferredoxin. These have been widely implicated in the regulation of (epi)genetic factors modulating growth and health of crop plants, with an agricultural context. In this regard, priming with the employment of chemical and biological agents has emerged as a fascinating approach to improve plant tolerance against various abiotic and biotic stressors. Priming in plants is a physiological process, where prior exposure to specific stressors induces a state of heightened alertness, enabling a more rapid and effective defense response upon subsequent encounters with similar challenges. Priming is reported to play a crucial role in the modulation of cellular redox homeostasis, maximizing crop productivity under stress conditions and thus achieving yield security. By taking this into consideration, the present review is an up-to-date critical evaluation of promising plant priming technologies and their role in the regulation of redox components toward enhanced plant adaptations to extreme unfavorable environmental conditions. The challenges and opportunities of plant priming are discussed, with an aim of encouraging future research in this field toward effective application of priming in stress management in crops including horticultural species.

Plant triterpenoid saponins function as susceptibility factors to promote the pathogenicity of Botrytis cinerea

The gray mold fungus Botrytis cinerea is a necrotrophic pathogen that causes diseases in hundreds of plant species, including high-value crops. Its polyxenous nature and pathogenic success are due to its ability to perceive host signals in its favor. In this study, we found that laticifer cells of Euphorbia lathyris are a source of susceptibility factors required by B. cinerea to cause disease. Consequently, poor-in-latex (pil) mutants, which lack laticifer cells, show full resistance to this pathogen, whereas lot-of-latex mutants, which produce more laticifer cells, are hypersusceptible. These S factors are triterpenoid saponins, which are widely distributed natural products of vast structural diversity. The downregulation of laticifer-specific oxydosqualene cyclase genes, which encode the first committed step enzymes for triterpene and, therefore, saponin biosynthesis, conferred disease resistance to B. cinerea. Likewise, the Medicago truncatula lha-1 mutant, compromised in triterpenoid saponin biosynthesis, showed enhanced resistance. Interestingly, the application of different purified triterpenoid saponins pharmacologically complemented the disease-resistant phenotype of pil and hla-1 mutants and enhanced disease susceptibility in different plant species. We found that triterpenoid saponins function as plant cues that signal transcriptional reprogramming in B. cinerea, leading to a change in its growth habit and infection strategy, culminating in the abundant formation of infection cushions, the multicellular appressoria apparatus dedicated to plant penetration and biomass destruction in B. cinerea. Taken together, these results provide an explanation for how plant triterpenoid saponins function as disease susceptibility factors to promote B. cinerea pathogenicity.

Comparative transcriptomic analysis of the nodulation-competent zone and inference of transcription regulatory network in silicon applied Glycine max [L.]-Merr. Roots

KEY MESSAGE

The study unveils Si's regulatory influence by regulating DEGs, TFs, and TRs. Further bHLH subfamily and auxin transporter pathway elucidates the mechanisms enhancing root development and nodulation. Soybean is a globally important crop serving as a primary source of vegetable protein for millions of individuals. The roots of these plants harbour essential nitrogen fixing structures called nodules. This study investigates the multifaceted impact of silicon (Si) application on soybean, with a focus on root development, and nodulation employing comprehensive transcriptomic analyses and gene regulatory network. RNA sequence analysis was utilised to examine the change in gene expression and identify the noteworthy differentially expressed genes (DEGs) linked to the enhancement of soybean root nodulation and root development. A set of 316 genes involved in diverse biological and molecular pathways are identified, with emphasis on transcription factors (TFs) and transcriptional regulators (TRs). The study uncovers TF and TR genes, categorized into 68 distinct families, highlighting the intricate regulatory landscape influenced by Si in soybeans. Upregulated most important bHLH subfamily and the involvement of the auxin transporter pathway underscore the molecular mechanisms contributing to enhanced root development and nodulation. The study bridges insights from other research, reinforcing Si's impact on stress-response pathways and phenylpropanoid biosynthesis crucial for nodulation. The study reveals significant alterations in gene expression patterns associated with cellular component functions, root development, and nodulation in response to Si.

Effects of Jasmonic Acid on Stress Response and Quality Formation in Vegetable Crops and Their Underlying Molecular Mechanisms

The plant hormone jasmonic acid plays an important role in plant growth and development, participating in many physiological processes, such as plant disease resistance, stress resistance, organ development, root growth, and flowering. With the improvement in living standards, people have higher requirements regarding the quality of vegetables. However, during the growth process of vegetables, they are often attacked by pests and diseases and undergo abiotic stresses, resulting in their growth restriction and decreases in their yield and quality. Therefore, people have found many ways to regulate the growth and quality of vegetable crops. In recent years, in addition to the role that JA plays in stress response and resistance, it has been found to have a regulatory effect on crop quality. Therefore, this study aims to review the jasmonic acid accumulation patterns during various physiological processes and its potential role in vegetable development and quality formation, as well as the underlying molecular mechanisms. The information provided in this manuscript sheds new light on the improvements in vegetable yield and quality.

OsPRMT6a-mediated arginine methylation of OsJAZ1 regulates jasmonate signaling and spikelet development in rice

Although both protein arginine methylation (PRMT) and jasmonate (JA) signaling are crucial for regulating plant development, the relationship between these processes in the control of spikelet development remains unclear. In this study, we used the CRISPR/Cas9 technology to generate two OsPRMT6a loss-of-function mutants that exhibit various abnormal spikelet structures. Interestingly, we found that OsPRMT6a can methylate arginine residues in JA signal repressors OsJAZ1 and OsJAZ7. We showed that arginine methylation of OsJAZ1 enhances the binding affinity of OsJAZ1 with the JA receptors OsCOI1a and OsCOI1b in the presence of JAs, thereby promoting the ubiquitination of OsJAZ1 by the SCFOsCOI1a/OsCOI1b complex and degradation via the 26S proteasome. This process ultimately releases OsMYC2, a core transcriptional regulator in the JA signaling pathway, to activate or repress JA-responsive genes, thereby maintaining normal plant (spikelet) development. However, in the osprmt6a-1 mutant, reduced arginine methylation of OsJAZ1 impaires the interaction between OsJAZ1 and OsCOI1a/OsCOI1b in the presence of JAs. As a result, OsJAZ1 proteins become more stable, repressing JA responses, thus causing the formation of abnormal spikelet structures. Moreover, we discovered that JA signaling reduces the OsPRMT6a mRNA level in an OsMYC2-dependent manner, thereby establishing a negative feedback loop to balance JA signaling. We further found that OsPRMT6a-mediated arginine methylation of OsJAZ1 likely serves as a switch to tune JA signaling to maintain normal spikelet development under harsh environmental conditions such as high temperatures. Collectively, our study establishes a direct molecular link between arginine methylation and JA signaling in rice.

A signaling cascade mediating fruit trait development via phosphorylation-modulated nuclear accumulation of JAZ repressor

It is generally accepted that jasmonate-ZIM domain (JAZ) repressors act to mediate jasmonate (JA) signaling via CORONATINE-INSENSITIVE1 (COI1)-mediated degradation. Here, we report a cryptic signaling cascade where a JAZ repressor, FvJAZ12, mediates multiple signaling inputs via phosphorylation-modulated subcellular translocation rather than the COI1-mediated degradation mechanism in strawberry (Fragaria vesca). FvJAZ12 acts to regulate flavor metabolism and defense response, and was found to be the target of FvMPK6, a mitogen-activated protein kinase that is capable of responding to multiple signal stimuli. FvMPK6 phosphorylates FvJAZ12 at the amino acid residues S179 and T183 adjacent to the PY residues, thereby attenuating its nuclear accumulation and relieving its repression for FvMYC2, which acts to control the expression of lipoxygenase 3 (FvLOX3), an important gene involved in JA biosynthesis and a diverse array of cellular metabolisms. Our data reveal a previously unreported mechanism for JA signaling and decipher a signaling cascade that links multiple signaling inputs with fruit trait development.

Genome-wide identification of the walnut MYC gene family and functional characterization of Xinjiang wild walnut under low-temperature stress

Introduction: MYC transcription factors are the basic regulators of the jasmonic acid signaling pathway and play important roles in plant growth and development and the response to adverse stress. In recent years, severe winter freezing and late spring frost in the main planting area of walnut in Xinjiang have affected the growth and development of walnut, which has become a prominent problem restricting walnut production. Xinjiang wild walnut is the only remaining wild species of walnuts in China, which contains a lot of genes with excellent traits, and is important for the cultivation and breeding. Methods: In this paper, the physicochemical properties and bioinformatics of MYC transcription factor members in walnut were analyzed, and the nine MYC were screened from the transcriptome data under low temperature stress. At last, we study the subcellular localizations and the expression patterns of the nine MYC members in Xinjiang wild walnut. Results: The results revealed that 30 MYC members were identified from published walnut whole-genome data, and their evolutionary relationships with Arabidopsis and poplar were divided into six groups according to clustering analysis, among which JrMYC22 and JrMYC23 had high homology with PtrMYC2b, which is induced by jasmonic acid in response to low-temperature stress. Walnut MYC members are unevenly distributed on 12 chromosomes. The prediction of promoter cis-acting elements of walnut MYC transcription factor family members revealed that cis-acting elements related to jasmonic acid and lowtemperature stress were the ones with the greatest number of members, with 12. In addition, all nine MYC family members in Xinjiang wild walnut plants responding to low-temperature stress exhibited strong fluorescence responses in the nucleus. The expression levels of these members in response to low-temperature stress revealed that JrMYC28, JrMYC31, JrMYC33, JrMYC34, and JrMYC35 were highly expressed, and it was hypothesized that JrMYC28, JrMYC31, JrMYC33, JrMYC34, and JrMYC35 might play a key role in the response to lowtemperature stress. Discussion: The results of this study provide a theoretical basis for further research on the functional mechanisms of the MYC transcription factor family members in walnut.

Identification of transcription factor genes responsive to MeJA and characterization of a LaMYC2 transcription factor positively regulates lycorine biosynthesis in Lycoris aurea

Jasmonates (JAs) are among the main phytohormones, regulating plant growth and development, stress responses, and secondary metabolism. As the major regulator of the JA signaling pathway, MYC2 also plays an important role in plant secondary metabolite synthesis and accumulation. In this study, we performed a comparative transcriptome analysis of Lycoris aurea seedlings subjected to methyl jasmonate (MeJA) at different treatment times. A total of 31,193 differentially expressed genes (DEGs) were identified by RNA sequencing. Among them, 732 differentially expressed transcription factors (TFs) comprising 51 TF families were characterized. The most abundant TF family was WRKY proteins (80), followed by AP2/ERF-EFR (67), MYB (59), bHLH (52), and NAC protein (49) families. Subsequently, by calculating the Pearson's correlation coefficient (PCC) between the expression level of TF DEGs and the lycorine contents, 41 potential TF genes (|PCC| >0.8) involved in lycorine accumulation were identified, including 36 positive regulators and 5 negative regulators. Moreover, a MeJA-inducible MYC2 gene (namely LaMYC2) was cloned on the basis of transcriptome sequencing. Bioinformatic analyses revealed that LaMYC2 proteins contain the bHLH-MYC_N domain and bHLH-AtAIB_like motif. LaMYC2 protein is localized in the cell nucleus, and can partly rescue the MYC2 mutant in Arabidopsis thaliana. LaMYC2 protein could interact with most LaJAZs (especially LaJAZ3 and LaJAZ4) identified previously. Transient overexpression of LaMYC2 increased lycorine contents in L. aurea petals, which might be associated with the activation of the transcript levels of tyrosine decarboxylase (TYDC) and phenylalanine ammonia lyase (PAL) genes. By isolating the 887-bp-length promoter fragment upstream of the start codon (ATG) of LaTYDC, we found several different types of E-box motifs (CANNTG) in the promoter of LaTYDC. Further study demonstrated that LaMYC2 was indeed able to bind the E-box (CACATG) present in the LaTYDC promoter, verifying that the pathway genes involved in lycorine biosynthesis could be regulated by LaMYC2, and that LaMYC2 has positive roles in the regulation of lycorine biosynthesis. These findings demonstrate that LaMYC2 is a positive regulator of lycorine biosynthesis and may facilitate further functional research of the LaMYC2 gene, especially its potential regulatory roles in Amaryllidaceae alkaloid accumulation in L. aurea.

Rice transcriptional repressor OsTIE1 controls anther dehiscence and male sterility by regulating JA biosynthesis

Proper anther dehiscence is essential for successful pollination and reproduction in angiosperms, and jasmonic acid (JA) is crucial for the process. However, the mechanisms underlying the tight regulation of JA biosynthesis during anther development remain largely unknown. Here, we demonstrate that the rice (Oryza sativa L.) ethylene-response factor-associated amphiphilic repression (EAR) motif-containing protein TEOSINTE BRANCHED1/CYCLOIDEA/PROLIFERATING CELL FACTORS (TCP) INTERACTOR CONTAINING EAR MOTIF PROTEIN1 (OsTIE1) tightly regulates JA biosynthesis by repressing TCP transcription factor OsTCP1/PCF5 during anther development. The loss of OsTIE1 function in Ostie1 mutants causes male sterility. The Ostie1 mutants display inviable pollen, early stamen filament elongation, and precocious anther dehiscence. In addition, JA biosynthesis is activated earlier and JA abundance is precociously increased in Ostie1 anthers. OsTIE1 is expressed during anther development, and OsTIE1 is localized in nuclei and has transcriptional repression activity. OsTIE1 directly interacts with OsTCP1, and overexpression of OsTCP1 caused early anther dehiscence resembling that of Ostie1. JA biosynthesis genes including rice LIPOXYGENASE are regulated by the OsTIE1-OsTCP1 complex. Our findings reveal that the OsTIE1-OsTCP1 module plays a critical role in anther development by finely tuning JA biosynthesis and provide a foundation for the generation of male sterile plants for hybrid seed production.

Regulatory networks in plant responses to drought and cold stress

Drought and cold represent distinct types of abiotic stress, each initiating unique primary signaling pathways in response to dehydration and temperature changes, respectively. However, a convergence at the gene regulatory level is observed where a common set of stress-responsive genes is activated to mitigate the impacts of both stresses. In this review, we explore these intricate regulatory networks, illustrating how plants coordinate distinct stress signals into a collective transcriptional strategy. We delve into the molecular mechanisms of stress perception, stress signaling, and the activation of gene regulatory pathways, with a focus on insights gained from model species. By elucidating both the shared and distinct aspects of plant responses to drought and cold, we provide insight into the adaptive strategies of plants, paving the way for the engineering of stress-resilient crop varieties that can withstand a changing climate.