Jasmonic Acid Signaling Research Articles

Azospirillum brasilense improves rice growth under salt stress by regulating the expression of key genes involved in salt stress response, abscisic acid signaling, and nutrient transport, among others.

Major food crops, such as rice and maize, display severe yield losses (30-50%) under salt stress. Furthermore, problems associated with soil salinity are anticipated to worsen due to climate change. Therefore, it is necessary to implement sustainable agricultural strategies, such as exploiting beneficial plant-microbe associations, for increased crop yields. Plants can develop associations with beneficial microbes, including arbuscular mycorrhiza and plant growth-promoting bacteria (PGPB). PGPB improve plant growth via multiple mechanisms, including protection against biotic and abiotic stresses. Azospirillum brasilense, one of the most studied PGPB, can mitigate salt stress in different crops. However, little is known about the molecular mechanisms by which A. brasilense mitigates salt stress. This study shows that total and root plant mass is improved in A. brasilense-inoculated rice plants compared to the uninoculated plants grown under high salt concentrations (100 mM and 200 mM NaCl). We observed this growth improvement at seven- and fourteen days post-treatment (dpt). Next, we used transcriptomic approaches and identified differentially expressed genes (DEGs) in rice roots when exposed to three treatments: 1) A. brasilense, 2) salt (200 mM NaCl), and 3) A. brasilense and salt (200 mM NaCl), at seven dpt. We identified 786 DEGs in the A. brasilense-treated plants, 4061 DEGs in the salt-stressed plants, and 1387 DEGs in the salt-stressed A. brasilense-treated plants. In the A. brasilense-treated plants, we identified DEGs involved in defense, hormone, and nutrient transport, among others. In the salt-stressed plants, we identified DEGs involved in abscisic acid and jasmonic acid signaling, antioxidant enzymes, sodium and potassium transport, and calcium signaling, among others. In the salt-stressed A. brasilense-treated plants, we identified some genes involved in salt stress response and tolerance (e.g., abscisic acid and jasmonic acid signaling, antioxidant enzymes, calcium signaling), and sodium and potassium transport differentially expressed, among others. We also identified some A. brasilense-specific plant DEGs, such as nitrate transporters and defense genes. Furthermore, our results suggest genes involved in auxin and ethylene signaling are likely to play an important role during these interactions. Overall, our transcriptomic data indicate that A. brasilense improves rice growth under salt stress by regulating the expression of key genes involved in defense and stress response, abscisic acid and jasmonic acid signaling, and ion and nutrient transport, among others. Our findings will provide essential insights into salt stress mitigation in rice by A. brasilense.

Comparison of Transcriptome between Tolerant and Susceptible Rice Cultivar Reveals Positive and Negative Regulators of Response to Rhizoctonia solani in Rice.

Rice (Oryza sativa L.) is one of the world's most crucial food crops, as it currently supports more than half of the world's population. However, the presence of sheath blight (SB) caused by Rhizoctonia solani has become a significant issue for rice agriculture. This disease is responsible for causing severe yield losses each year and is a threat to global food security. The breeding of SB-resistant rice varieties requires a thorough understanding of the molecular mechanisms involved and the exploration of immune genes in rice. To this end, we conducted a screening of rice cultivars for resistance to SB and compared the transcriptome based on RNA-seq between the most tolerant and susceptible cultivars. Our study revealed significant transcriptomic differences between the tolerant cultivar ZhengDao 22 (ZD) and the most susceptible cultivar XinZhi No.1 (XZ) in response to R. solani invasion. Specifically, the tolerant cultivar showed 7066 differentially expressed genes (DEGs), while the susceptible cultivar showed only 60 DEGs. In further analysis, we observed clear differences in gene category between up- and down-regulated expression of genes (uDEGs and dDEGs) based on Gene Ontology (GO) classes in response to infection in the tolerant cultivar ZD, and then identified uDEGs related to cell surface pattern recognition receptors, the Ca2+ ion signaling pathway, and the Mitogen-Activated Protein Kinase (MAPK) cascade that play a positive role against R. solani. In addition, DEGs of the jasmonic acid and ethylene signaling pathways were mainly positively regulated, whereas DEGs of the auxin signaling pathway were mainly negatively regulated. Transcription factors were involved in the immune response as either positive or negative regulators of the response to this pathogen. Furthermore, our results showed that chloroplasts play a crucial role and that reduced photosynthetic capacity is a critical feature of this response. The results of this research have important implications for better characterization of the molecular mechanism of SB resistance and for the development of resistant cultivars through molecular breeding methods.

Comprehensive analysis of OsJAZ gene family deciphers rhizobacteria-mediated nutrient stress modulation in rice

The JASMONATE-ZIM DOMAIN (JAZ) repressors are crucial proteins in jasmonic acid signaling pathway that are critical for plant growth. Therefore, the present study aimed to identify and characterize OsJAZs in the rice genome, revealing their structural attributes, regulatory elements, miRNA interactions, and subcellular localization. 23 JAZ transcripts across the 6 chromosomes of rice genome were identified having conserved domains and different physiochemical characteristics. Phylogenetically classified into five clades, they showed highest syntenic relationship with P. virgatum. The non-synonymous/synonymous values ranged from 0.44 to 1.21 suggesting purifying/stabilizing selection in OsJAZs. The study examined the 1.5 kb promoter region for cis-regulatory elements, and also identified 92 miRNAs targets. Furthermore, homology modeling provided insights into the 3D-structures of JAZ proteins while in-silico gene expression analysis revealed their functional diversity in various tissues and developmental stages. Additionally, qRT-PCR analysis highlighted their involvement in stress adaptation to sub-optimum nutrient conditions induced by plant-beneficial rhizobacteria Bacillus amyloliquefaciens (SN13) in two rice varieties. Distinct OsJAZ expression patterns in the two varieties correlated with altered root architecture, xylem structure, and lignification. These findings affirmed that specific up-or down-regulation of OsJAZs might play critical role in SN13 induced changes in the two varieties that enabled them to survive under stress.

More than trichomes and acylsugars: the role of jasmonic acid as mediator of aphid resistance in tomato

ABSTRACT This study investigates the impact of priming on the resistance of tomato plants to the potato aphid Macrosiphum euphorbiae, focusing on the role of glandular trichomes. Glandular trichomes are specific hairs that provide protection to tomato plants against herbivorous insects. The experimental priming conducted in this study revealed that prior infestation by Spodoptera littoralis caterpillars increased the plant's resistance against M. euphorbiae, pointing at the jasmonic acid (JA) signaling pathway in regulating this plant-aphid interaction. Glandular trichomes type IV were effective against aphids regardless of the previous infestation. Using JA-deficient tomato (spr2), we observed that M. euphorbiae multiplication increased, while the number of aphids on salicylic -deficient NahG plants was lower than in the wildtype Moneymaker. These findings emphasize the crucial role of the JA signaling pathway in tomato plant resistance to aphids and the importance of glandular trichomes to enhance plant defences against pests.

Physiological, Proteomic, and Resin Yield-Related Genes Expression Analysis Provides Insights into the Mechanisms Regulating Resin Yield in Masson Pine.

Masson pine (Pinus massoniana Lamb.) is an important resin-producing conifer species in China. Resin yield is a highly heritable trait and varies greatly among different genotypes. However, the mechanisms regulating the resin yield of masson pine remain largely unknown. In this study, physiological, proteomic, and gene expression analysis was performed on xylem tissues of masson pine with high and low resin yield. Physiological investigation showed that the activity of terpene synthase, as well as the contents of soluble sugar, jasmonic acid (JA), methyl jasmonate (MeJA), gibberellins (GA1, GA4, GA9, GA19, and GA20), indole-3-acetic acid (IAA), and abscisic acid (ABA) were significantly increased in the high yielder, whereas sucrose and salicylic acid (SA) were significantly decreased compared with the low one. A total of 2984 differentially expressed proteins (DEPs) were identified in four groups, which were mainly enriched in the biosynthesis of secondary metabolites, protein processing in the endoplasmic reticulum, carbohydrate metabolism, phytohormone biosynthesis, glutathione metabolism, and plant-pathogen interaction. Integrated physiological and proteomic analysis revealed that carbohydrate metabolism, terpenoid biosynthesis, resistance to stress, as well as JA and GA biosynthesis and signaling, play key roles in regulating resin yield. A series of proteins associated with resin yield, e.g., terpene synthase proteins (TPSs), ATP-binding cassette transporters (ABCs), glutathione S-transferase proteins (GSTs), and heat shock proteins (HSPs), were identified. Resin yield-related gene expression was also associated with resin yield. Our study unveils the implicated molecular mechanisms regulating resin yield and is of pivotal significance to breeding strategies of high resin-yielding masson pine cultivars.

Examining the Transcriptomic and Biochemical Signatures of Bacillus subtilis Strains: Impacts on Plant Growth and Abiotic Stress Tolerance.

Rhizobacteria from various ecological niches display variations in physiological characteristics. This study investigates the transcriptome profiling of two Bacillus subtilis strains, BsCP1 and BsPG1, each isolated from distinct environments. Gene expression linked to the synthesis of seven types of antibiotic compounds was detected in both BsCP1 and BsPG1 cultures. Among these, the genes associated with plipastatin synthesis were predominantly expressed in both bacterial strains. However, genes responsible for the synthesis of polyketide, subtilosin, and surfactin showed distinct transcriptional patterns. Additionally, genes involved in producing exopolysaccharides (EPS) showed higher expression levels in BsPG1 than in BsCP1. Consistently with this, a greater quantity of EPS was found in the BsPG1 culture compared to BsCP1. Both bacterial strains exhibited similar effects on Arabidopsis seedlings, promoting root branching and increasing seedling fresh weight. However, BsPG1 was a more potent enhancer of drought, heat, and copper stress tolerance than BsCP1. Treatment with BsPG1 had a greater impact on improving survival rates, increasing starch accumulation, and stabilizing chlorophyll content during the post-stress stage. qPCR analysis was used to measure transcriptional changes in Arabidopsis seedlings in response to BsCP1 and BsPG1 treatment. The results show that both bacterial strains had a similar impact on the expression of genes involved in the salicylic acid (SA) and jasmonic acid (JA) signaling pathways. Likewise, genes associated with stress response, root development, and disease resistance showed comparable responses to both bacterial strains. However, treatment with BsCP1 and BsPG1 induced distinct activation of genes associated with the ABA signaling pathway. The results of this study demonstrate that bacterial strains from different ecological environments have varying abilities to produce beneficial metabolites for plant growth. Apart from the SA and JA signaling pathways, ABA signaling triggered by PGPR bacterial strains could play a crucial role in building an effective resistance to various abiotic stresses in the plants they colonize.

Humic Substances Isolated from Recycled Biomass Trigger Jasmonic Acid Biosynthesis and Signalling.

Intensive agriculture maintains high crop yields through chemical inputs, which are well known for their adverse effects on environmental quality and human health. Innovative technologies are required to reduce the risk generated by the extensive and harmful use of pesticides. The plant biostimulants made from humic substances isolated from recyclable biomass offer an alternative approach to address the need for replacing conventional agrochemicals without compromising the crop yield. The stimulatory effects of humic substances are commonly associated with plant hormones, particularly auxins. However, jasmonic acid (JA) is crucial metabolite in mediating the defence responses and governing plant growth and development. This work aimed to evaluate the changes in the biosynthesis and signalling pathway of JA in tomato seedlings treated with humic acids (HA) isolated from vermicompost. We use the tomato model system cultivar Micro-Tom (MT) harbouring a reporter gene fused to a synthetic promoter that responds to jasmonic acid (JERE::GUS). The transcript levels of genes involved in JA generation and activity were also determined using qRT-PCR. The application of HA promoted plant growth and altered the JA status, as revealed by both GUS and qRT-PCR assays. Both JA enzymatic synthesis (LOX, OPR3) and JA signalling genes (JAZ and JAR) were found in higher transcription levels in plants treated with HA. In addition, ethylene (ETR4) and auxin (ARF6) signalling components were positively modulated by HA, revealing a hormonal cross-talk. Our results prove that the plant defence system linked to JA can be emulated by HA application without growth inhibition.

Induction of glandular trichomes to control whitefly-transmitted viruses in tomato crops: modulation by the natural enemy Nesidiocoris tenuis.

Whitefly-transmitted viruses are one of the biggest threats to tomato growing worldwide. Strategies based on the introgression of resistance traits from wild relatives are promoted to control tomato pests and diseases. Recently, a trichome-based resistance characterizing the wild species Solanum pimpinellifolium was introgressed into a cultivated tomato. An advanced backcross line (BC5S2) exhibiting the presence of acylsugars-associated type IV trichomes, which are lacking in cultivated tomatoes, was effective at controlling whiteflies (Hemiptera: Aleyrodidae) and limiting the spread of whitefly-transmitted viruses. However, at early growth stages, type IV trichomes density and acylsugars production are limited; thus, protection against whiteflies and whitefly-transmitted viruses remains irrelevant. In this work, we demonstrate that young BC5S2 tomato plants feeding-punctured by the zoophytophagous predator Nesidiocoris tenuis (Reuter) (Hemiptera: Miridae) displayed an increase (above 50%) in type IV trichomes density. Acylsugars production was consistently increased in N. tenuis-punctured BC5S2 plants, which was more likely associated with upregulated expression of BCKD-E2 gene related to acylsugars biosynthesis. In addition, the infestation of BC5S2 plants with N. tenuis effectively induced the expression of defensive genes involved in the jasmonic acid signaling pathway, resulting in strong repellence to B. tabaci and attractiveness to N. tenuis. Thus, by pre-plant release of N. tenuis in tomato nurseries carried out in some integrated pest management programs, type IV trichome-expressing plants can be prepared to control whiteflies and whitefly-transmitted viruses at early growth stages. This study emphasizes the advantage of reinforcing constitutive resistance using defense inducers to guarantee robust protection against pests and transmitted viruses.

Spermine deficiency shifts the balance between jasmonic acid and salicylic acid-mediated defence responses in Arabidopsis.

Polyamines are small aliphatic polycations present in all living organisms. In plants, the most abundant polyamines are putrescine (Put), spermidine (Spd) and spermine (Spm). Polyamine levels change in response to different pathogens, including Pseudomonas syringae pv. tomato DC3000 (Pst DC3000). However, the regulation of polyamine metabolism and their specific contributions to defence are not fully understood. Here we report that stimulation of Put biosynthesis by Pst DC3000 is dependent on coronatine (COR) perception and jasmonic acid (JA) signalling, independently of salicylic acid (SA). Conversely, lack of Spm in spermine synthase (spms) mutant stimulated galactolipids and JA biosynthesis, and JA signalling under basal conditions and during Pst DC3000 infection, whereas compromised SA-pathway activation and defence outputs through SA-JA antagonism. The dampening of SA responses correlated with COR and Pst DC3000-inducible deregulation of ANAC019 expression and its key SA-metabolism gene targets. Spm deficiency also led to enhanced disease resistance to the necrotrophic fungal pathogen Botrytis cinerea and stimulated endoplasmic reticulum (ER) stress signalling in response to Pst DC3000. Overall, our findings provide evidence for the integration of polyamine metabolism in JA- and SA-mediated defence responses, as well as the participation of Spm in buffering ER stress during defence.

VvWRKY5 enhances white rot resistance in grape by promoting the jasmonic acid pathway.

Grape white rot is a disease caused by Coniella diplodiella (Speg.) Sacc. (Cd) can drastically reduce the production and quality of grape (Vitis vinifera). WRKY transcription factors play a vital role in the regulation of plant resistance to pathogens, but their functions in grape white rot need to be further explored. Here, we found that the expression of the WRKY IIe subfamily member VvWRKY5 was highly induced by Cd infection and jasmonic acid (JA) treatment. Transient injection and stable overexpression (in grape calli and Arabidopsis) demonstrated that VvWRKY5 positively regulated grape resistance to white rot. We also determined that VvWRKY5 regulated the JA response by directly binding to the promoters of VvJAZ2 (a JA signaling suppressor) and VvMYC2 (a JA signaling activator), thereby inhibiting and activating the transcription of VvJAZ2 and VvMYC2, respectively. Furthermore, the interaction between VvJAZ2 and VvWRKY5 enhanced the suppression and promotion of VvJAZ2 and VvMYC2 activities by VvWRKY5, respectively. When VvWRKY5 was overexpressed in grape, JA content was also increased. Overall, our results suggested that VvWRKY5 played a key role in regulating JA biosynthesis and signal transduction as well as enhancing white rot resistance in grape. Our results also provide theoretical guidance for the development of elite grape cultivars with enhanced pathogen resistance.

JA-mediated MYC2/LOX/AOS feedback loop regulates osmotic stress response in tea plant

Osmotic stress caused by low-temperature, drought and salinity was a prevalent abiotic stress in plant that severely inhibited plant development and agricultural yield, particularly in tea plant. Jasmonic acid (JA) is an important phytohormone involving in plant stress. However, underlying molecular mechanisms of JA modulated osmotic stress response remains unclear. In this study, high concentration of mannitol induced JA accumulation and increase of peroxidase activity in tea plant. Integrated transcriptome mined a JA signaling master, MYC2 transcription factor is shown as a hub regulator that induced by mannitol, expression of which positively correlated with JA biosynthetic genes (LOX and AOS) and peroxidase genes (PER). CsMYC2 was determined as a nuclei-localized transcription activator, furthermore, Protein-DNA interaction analysis indicated that CsMYC2 was positive regulator that activated the transcription of CsLOX7, CsAOS2, CsPER1 and CsPER3 via bound with their promoters, respectively. Suppression of CsMYC2 expression resulted in a reduced JA content and peroxidase activity and osmotic stress tolerance of tea plant. Overexpression of CsMYC2 in Arabidopsis improved JA content, peroxidase activity and plants tolerance against mannitol stress. Together, we proposed a positive feedback loop mediated by CsMYC2, CsLOX7 and CsAOS2 which constituted to increase the tolerance of osmotic stress through fine-tuning the accumulation of JA levels and increase of POD activity in tea plant.

Transcriptome analysis of two tobacco varieties with contrast resistance to Meloidogyne incognita in response to PVY MSNR infection.

Root-knot nematode (RKN) disease is a major disease of tobacco worldwide, which seriously hinders the improvement of tobacco yield and quality. Obvious veinal necrosis-hypersensitive responses are observed only in RKN-resistant lines infected by Potyvirus Y (PVY) MSNR, making this an effective approach to screen for RKN-resistant tobacco. RNA-seq analysis, real-time quantitative PCR (qRT-PCR) and functional enrichment analysis were conducted to gain insight into the transcription dynamics difference between G28 (RKN-resistant) and CBH (RKN-susceptible) varieties infected with PVY MSNR. Results showed that a total of 7900, 10576, 9921, 11530 and 12531 differentially expressed genes (DEGs) were identified between the two varieties at 0, 1, 3, 5, and 7 d after infection, respectively. DEGs were associated with plant hormone signal transduction, starch and sucrose metabolism, phenylpropanoid biosynthesis, and photosynthesis-related metabolic pathways. Additional DEGs related to starch and sucrose metabolism, energy production, and the indole-3-acetic acid signaling pathway were induced in CBH plants after infection. DEGs related to phenylpropanoid biosynthesis, abscisic acid, salicylic acid, brassinosteroids, and jasmonic acid signaling pathway were induced in G28 after infection. Our findings reveal DEGs that may contribute to differences in PVY MSNR resistance among tobacco varieties. These results help us to understand the differences in transcriptional dynamics and metabolic processes between RKN-resistant and RKN-susceptible varieties involved in tobacco-PVY MSNR interaction.

Auxin in Plant Defense Reactions: New Insights and Potential Applications for Resistance Breeding Programmes

The role of auxin in growth and development in plants has been studied and documented since its discovery; however, its role in plant defense during pathogenic infection has been studied more recently. With the aim to provide new insights and update knowledge in this field of biology, this review was carried out focusing on the specific role of auxin and associated signaling against a wide array of bacterial and fungal pathogens, as special references. This review illustrates the role of auxin including indole-3-acetic acid, mechanism of auxin-responsive gene action, auxin signaling and associated crosstalk with other defense hormone pathways. Loads of evidence support that the biology of plants favoring repressed auxin signaling, auxin responsive defense gene activation and hormonal crosstalk with other associated defense hormones such as salicylic acid and jasmonic acid signaling pathway is vital for host defense against pathogens. As this paper unravels the role of auxin in plant defense, classical and molecular breeders would get new background insight into engineering plants with enhanced host plant resistance with the introduction of auxin responsive gene or manipulation of desirable auxin signaling or associated pathway. The current knowledge domain on plant defense during pathogen infection could be improved by considering multiple pathogens in nature, their interaction with other beneficial microbes and associated auxin manipulation in future research works.

Spliceosomal protein U2B″ delays leaf senescence by enhancing splicing variant JAZ9β expression to attenuate jasmonate signaling in Arabidopsis.

The regulatory framework of leaf senescence is gradually becoming clearer; however, the fine regulation of this process remains largely unknown. Here, genetic analysis revealed that U2 small nuclear ribonucleoprotein B (U2B″), a component of the spliceosome, is a negative regulator of leaf senescence. Mutation of U2B″ led to precocious leaf senescence, whereas overexpression of U2B″ extended leaf longevity. Transcriptome analysis revealed that the jasmonic acid (JA) signaling pathway was activated in the u2b″ mutant. U2B″ enhances the generation of splicing variant JASMONATE ZIM-DOMAIN 9β (JAZ9β) with an intron retention in the Jas motif, which compromises its interaction with CORONATINE INSENSITIVE1 and thus enhances the stability of JAZ9β protein. Moreover, JAZ9β could interact with MYC2 and obstruct its activity, thereby attenuating JA signaling. Correspondingly, overexpression of JAZ9β rescued the early senescence phenotype of the u2b″ mutant. Furthermore, JA treatment promoted expression of U2B″ that was found to be a direct target of MYC2. Overexpression of MYC2 in the u2b″ mutant resulted in a more pronounced premature senescence than that in wild-type plants. Collectively, our findings reveal that the spliceosomal protein U2B″ fine-tunes leaf senescence by enhancing the expression of JAZ9β and thereby attenuating JA signaling.

6-Benzylaminopurine as a potential fresh-keeping agent for Curcuma alismatifolia cut flowers: Physiological and transcriptome analysis

Curcuma alismatifolia is a significant cut flower, but its postharvest preservation remains challenging. 6-benzylaminopurine (6-BA) can effectively delay senescence in various horticultural plants. This study demonstrated that soaking and spraying 6-BA significantly extended the vase life of four C. alismatifolia varieties, particularly ‘Siam Shadow’, which had the longest vase life extension of 5.1 days by spraying and 3.7 days by soaking. Further analyses of physiological, biochemical, and transcriptomic indicators were conducted on the bracts of ‘Siam Shadow’ under 50 mg/L 6-BA spraying treatment and control at three senescence stages: S1 (4th day), S2 (8th day), and S3 (12th day) after vase placement. The results indicated that 6-BA spraying increased superoxide dismutase (SOD) and catalase (CAT) activities in S1 and S2 while increasing peroxidase (POD) and decreasing jasmonic acid (JA) contents in all stages. Orthogonal Partial Least Squares-Discriminant Analysis (OPLS-DA) identified JA content as the key differential indicator of 6-BA treatment. Transcriptome analysis revealed that 6-BA treatment upregulated 102 antioxidant-related genes and downregulated 27 JA biosynthesis-related genes and 16 JA signal transduction-related genes in all stages. Among them, the gene families of POD, LOX, and JAZ, which are involved in peroxidase activity, JA biosynthesis, and JA signal transduction, respectively, may play major roles in delaying C. alismatifolia bract senescence. Moreover, correlation network analysis showed that 198 senescence-related transcription factors (WRKYs, NACs, etc.) were significantly correlated with 77 antioxidant-related genes, 22 JA biosynthesis-related genes, and 12 JA signal transduction-related genes. These findings suggest that 6-BA is a potential preservative for C. alismatifolia cut flowers and that it may primarily affect the expression of genes related to senescence-associated transcription factors, JA biosynthesis and signal transduction, and antioxidant enzymes, thereby reducing JA content and enhancing antioxidant enzyme activities, consequently delaying C. alismatifolia bract senescence.

Biosynthesis, herbivore induction, and defensive role of phenylacetaldoxime glucoside.

Aldoximes are well-known metabolic precursors for plant defense compounds such as cyanogenic glycosides, glucosinolates, and volatile nitriles. They are also defenses themselves produced in response to herbivory; however, it is unclear whether aldoximes can be stored over a longer term as defense compounds and how plants protect themselves against the potential autotoxic effects of aldoximes. Here, we show that the Neotropical myrmecophyte tococa (Tococa quadrialata, recently renamed Miconia microphysca) accumulates phenylacetaldoxime glucoside (PAOx-Glc) in response to leaf herbivory. Sequence comparison, transcriptomic analysis, and heterologous expression revealed that 2 cytochrome P450 enzymes, CYP79A206 and CYP79A207, and the UDP-glucosyltransferase UGT85A123 are involved in the formation of PAOx-Glc in tococa. Another P450, CYP71E76, was shown to convert PAOx to the volatile defense compound benzyl cyanide. The formation of PAOx-Glc and PAOx in leaves is a very local response to herbivory but does not appear to be regulated by jasmonic acid signaling. In contrast to PAOx, which was only detectable during herbivory, PAOx-Glc levels remained high for at least 3 d after insect feeding. This, together with the fact that gut protein extracts of 3 insect herbivore species exhibited hydrolytic activity toward PAOx-Glc, suggests that the glucoside is a stable storage form of a defense compound that may provide rapid protection against future herbivory. Moreover, the finding that herbivory or pathogen elicitor treatment also led to the accumulation of PAOx-Glc in 3 other phylogenetically distant plant species suggests that the formation and storage of aldoxime glucosides may represent a widespread plant defense response.

Roles of the pepper JAZ protein CaJAZ1-03 and its interacting partner RING-type E3 ligase CaASRF1 in regulating ABA signaling and drought responses.

Plants have developed various defense mechanisms against environmental stresses by regulating hormone signaling. Jasmonic acid (JA) is a major phytohormone associated with plant defense responses. JASMONATE ZIM-DOMAIN (JAZ) proteins play a regulatory role in repressing JA signaling, impacting plant responses to both biotic and abiotic stresses. Here, we isolated 7 JAZ genes in pepper and selected CA03g31030, a Capsicum annuum JAZ1-03 (CaJAZ1-03) gene, for further study based on its expression level in response to abiotic stresses. Through virus-induced gene silencing (VIGS) in pepper and overexpression in transgenic Arabidopsis plants, we established the functional role of CaJAZ1-03. Functional studies revealed that CaJAZ1-03 dampens abscisic acid (ABA) signaling and drought stress responses. The cell-free degradation assay showed faster degradation of CaJAZ1-03 in drought- or ABA-treated pepper leaves compared to healthy leaves. Conversely, CaJAZ1-03 was completely preserved under MG132 treatment, indicating that CaJAZ1-03 stability ismodulated via the ubiquitin-26s proteasome pathway. We also found that the pepper RING-type E3 ligase CaASRF1 interacts with and ubiquitinates CaJAZ1-03. Additional cell-free degradation assays revealed a negative correlation between CaJAZ1-03 andCaASRF1 expression levels. Collectively, these findings suggest that CaJAZ1-03 negatively regulates ABA signaling and drought responses and that its protein stability is modulated by CaASRF1.

Transcriptome analysis during vernalization in wheat (Triticum aestivum L.)

BackgroundVernalization, as a vital process in the life cycle of winter cereal, has important effects on floral organ formation and flowering time. Many morphological changes together with molecular changes occur during the vernalization period. Here, we used transcriptome sequencing to analyze the transcriptomic changes in wheat leaves before, during and after vernalization using the winter wheat cultivar ‘Shiluan02-1’.ResultsA total of 16,370 differentially expressed genes were obtained across different vernalization periods. Gene Ontology enrichment analysis revealed that photoperiodism, photoprotection, photosynthesis, lipid transport and biosynthetic process, and chlorophyll metabolic process were closely related to vernalization. In addition, AP2/ERF, C2H2, bHLH, WRKY, MYB, MYB-related, and NAC transcription factors were significantly enriched during vernalization, and the transcription factor expression patterns suggested the intricate regulation of transcription factor modules in plant vernalization pathways. Analysis of gene expression patterns of the MADS-box transcription factor genes showed different expression patterns during vernalization phases, among which VERNALIZATION1 (VRN1) genes were found to gradually increase during vernalization periods from V0 to V35, while decline in the V42 phase, then increase after vernalization. The Tavrt-2 gene cooperated with Tavrn1 to regulate flowering induced by vernalization, and its expression level was rapidly increased by vernalization but declined in the V42 phase and then increased after vernalization. Some genes from the ICE-CBF-COR pathway were also identified, and additional analysis indicated that some key genes related to phytohormone biosynthesis and signal transduction were enriched during the vernalization period, such as gibberellic acid, ethylene, abscisic acid and jasmonic acid biosynthesis and signaling pathway genes.ConclusionsOur study provides valuable molecular information for future studies on wheat vernalization regulation and also serves as an excellent reference for future wheat breeding.

SlMsrB5 contributes to the chilling tolerance induced by methyl jasmonate in postharvest tomato fruit

Chilling injury (CI) is a common phenomenon during low temperature storage for most fruits, reducing the effectiveness of refrigeration methods. Methyl jasmonate (MeJA) has been extensively employed to extend the shelf life of fruits during cold storage. However, the mechanism of MeJA inducing fruit resistance to CI requires further investigation. The study found that treating tomatoes with 0.05 mM MeJA inhibited CI by regulating the reactive oxygen species (ROS) metabolism, polyamines, and jasmonic acid (JA) signaling pathway, as well as cold response pathway. Interestingly, the expression of SlMsrB5 in tomato was up-regulated under MeJA treatment, showing an increase of 36.44% to 161.75% compared to the control fruit. Notably, silencing the expression of SlMsrB5 led to a continuously increased in CI incidence by 52.17% and CI index by 36.58% compared to the control fruit at the end of storage. Additionally, the silencing of SlMsrB5 weakened the inhibitory impact of MeJA on CI and reduced its induction effects on the aforementioned indicators. In addition, correlation analysis showed that the transcription of SlMsrB5 has a negative correlation with ROS related indicators under MeJA treatment, while was highly correlated with the aforementioned induction effects controlled by MeJA. Therefore, this study demonstrates a new basis for revealing the underlying mechanisms in the MeJA-regulated chilling resistance in postharvest fruits.

Roles and Preliminary Mechanism of Tobacco cis-Abienol in Inducing Tomato Resistance against Bacterial Wilt.

Bacterial wilt negatively impacts the yield and quality of tomatoes. cis-Abienol, a labdane diterpenoid abundantly produced in the trichome secretion of Nicotiana spp., can induce bacterial wilt resistance in plants; however, study on its practical application and acting mechanism is very limited. This study established the application conditions of cis-abienol for inducing tomato bacterial wilt resistance by pot-inoculation experiments and investigated the underlying mechanism by determining the physio-biochemical indexes and transcriptomic changes. The results showed that applying cis-abienol to the roots was the most effective approach for inducing tomato bacterial wilt resistance. The optimal concentration was 60 μg/mL, and 2-3 consecutive applications with 3-6 days intervals were sufficient to induce the bacterial wilt resistance of tomato plants. cis-Abienol could enhance the antioxidant enzyme activity and stimulate the defensive signal transduction in tomato roots, leading to the upregulation of genes involved in the mitogen-activated protein kinase cascade. It also upregulated the expression of JAZ genes and increased the content of jasmonic acid (JA) and salicylic acid (SA), which control the expression of flavonoid biosynthetic genes and the content of phytoalexins in tomato roots. cis-Abienol-induced resistance mainly depends on the JA signalling pathway, and the SA signalling pathway is also involved in this process. This study established the feasibility of applying the plant-derived terpenoid cis-abienol to induce plant bacterial wilt resistance, which is of great value for developing eco-friendly bactericides.