Exogenous application of methyl jasmonate induces defense response and develops tolerance against mungbean yellow mosaic India virus in Vigna mungo

Metabolomics combined with physiology and transcriptomics reveal how Nicotiana tabacum leaves respond to cold stress

Low temperature-induced cold stress is a major threat to plant growth, development and distribution. Unraveling the responses of temperature-sensitive crops to cold stress and the mechanisms of cold acclimation are critical for food demand. In this study, combined physiological, transcriptomic, and metabolomic analyses were conducted on Nicotiana tabacum suffering short-term 4 °C cold stress. Our results showed that cold stress destroyed cellular membrane stability, decreased the chlorophyll (Chl) and carotenoid contents, and closed stomata, resulting in lipid peroxidation and photosynthesis restriction. Chl fluorescence measurements revealed that primary photochemistry, photoelectrochemical quenching and photosynthetic electron transport in Nicotiana tabacum leaves were seriously suppressed upon exposer to cold stress. Enzymatic and nonenzymatic antioxidants, including superoxide dismutase, catalase, peroxidase, reduced glutathione, proline, and soluble sugar, were all profoundly increased to trigger the cold acclimation defense against oxidative damage. A total of 178 metabolites and 16,204 genes were differentially expressed in cold-stressed Nicotiana tabacum leaves. MEturquoise and MEblue modules identified by WGCNA were highly correlated with physiological indices, and the corresponding hub genes were significantly enriched in pathways related to photosynthesis - antenna proteins and flavonoid biosynthesis. Untargeted metabolomic analysis identified specific metabolites, including sucrose, phenylalanine, glutamine, glutamate, and proline, that enhance plant cold acclimation. Combined transcriptomics and metabolomic analysis highlight the vital roles of carbohydrate and amino acid metabolism in enhancing the cold tolerance of Nicotiana tabacum. Our comprehensive investigation provides novel insights for efforts to alleviate low temperature-induced oxidative damage to Nicotiana tabacum plants and proposes a breeding target for cold stress-tolerant cultivars.

Join the green team: Inducers of plant immunity in the plant disease sustainable control toolbox

BACKGROUND

Crops are constantly attacked by various pathogens. These pathogenic microorganisms, such as fungi, oomycetes, bacteria, viruses, and nematodes, threaten global food security by causing detrimental crop diseases that generate tremendous quality and yield losses worldwide. Chemical pesticides have undoubtedly reduced crop damage; however, in addition to increasing the cost of agricultural production, the extensive use of chemical pesticides comes with environmental and social costs. Therefore, it is necessary to vigorously develop sustainable disease prevention and control strategies to promote the transition from traditional chemical control to modern green technologies. Plants possess sophisticated and efficient defense mechanisms against a wide range of pathogens naturally. Immune induction technology based on plant immunity inducers can prime plant defense mechanisms and greatly decrease the occurrence and severity of plant diseases. Reducing the use of agrochemicals is an effective way to minimize environmental pollution and promote agricultural safety.

AIM OF REVIEW

The purpose of this workis to offer valuable insights into the current understanding and future research perspectives of plant immunity inducers and their uses in plant disease control, ecological and environmental protection, and sustainable development of agriculture.

KEY SCIENTIFIC CONCEPTS OF REVIEW

In this work, we have introduced the concepts of sustainable and environment-friendly concepts of green disease prevention and control technologies based on plant immunity inducers. This article comprehensively summarizes these recent advances, emphasizes the importance of sustainable disease prevention and control technologies for food security, and highlights the diverse functions of plant immunity inducers-mediated disease resistance. The challenges encountered in the potential applications of plant immunity inducers and future research orientation are also discussed.

Methyl jasmonate improves resistance in scab-susceptible Red Delicious apple by altering ROS homeostasis and enhancing phenylpropanoid biosynthesis

Apple (Malus domestica) is an economically important rosaceous fruit crop grown at temperate climate zones. Nevertheless, its production is severely affected by scab disease caused by the ascomycetous fungus Venturia inaequalis (VI). Methyl jasmonate (MeJA) is a stress induced plant hormone, shown to induce resistance against wide range of pathogens. The current study investigated the role of MeJA in promoting scab tolerance in susceptible apple varieties through exogenous application of optimized (100 μM) MeJA concentration, followed by VI infection. According to our analysis, applying MeJA exogenously onto leaf surfaces resulted in increased membrane stability and decreased malondialdehyde levels in Red Delicious, suggesting that MeJA is capable of protecting tissues against oxidative damage through its role in restoring membrane stability. In addition, the changes in the levels of key antioxidative enzymes and reactive oxygen species (ROS) showed that exogenous MeJA maintains ROS homeostasis as well. Higher phenylalanine ammonia-lyase activity and increased accumulation of phenylpropanoids in MeJA-treated VI-infected plants indicated the MeJA reprogrammed phenylpropanoid biosynthesis pathway for scab tolerance. Our study of scab tolerance in apples induced by MeJA provides new insights into its physiological and biochemical mechanisms.

The transcriptional regulator JAZ8 interacts with the C2 protein from geminiviruses and limits the geminiviral infection in Arabidopsis

Jasmonates (JAs) are phytohormones that finely regulate critical biological processes, including plant development and defense. JASMONATE ZIM-DOMAIN (JAZ) proteins are crucial transcriptional regulators that keep JA-responsive genes in a repressed state. In the presence of JA-Ile, JAZ repressors are ubiquitinated and targeted for degradation by the ubiquitin/proteasome system, allowing the activation of downstream transcription factors and, consequently, the induction of JA-responsive genes. A growing body of evidence has shown that JA signaling is crucial in defending against plant viruses and their insect vectors. Here, we describe the interaction of C2 proteins from two tomato-infecting geminiviruses from the genus Begomovirus, tomato yellow leaf curl virus (TYLCV) and tomato yellow curl Sardinia virus (TYLCSaV), with the transcriptional repressor JAZ8 from Arabidopsis thaliana and its closest orthologue in tomato, SlJAZ9. Both JAZ and C2 proteins colocalize in the nucleus, forming discrete nuclear speckles. Overexpression of JAZ8 did not lead to altered responses to TYLCV infection in Arabidopsis; however, knock-down of JAZ8 favors geminiviral infection. Low levels of JAZ8 likely affect the viral infection specifically, since JAZ8-silenced plants neither display obvious developmental phenotypes nor present differences in their interaction with the viral insect vector. In summary, our results show that the geminivirus-encoded C2 interacts with JAZ8 in the nucleus, and suggest that this plant protein exerts an anti-geminiviral effect.

Transcriptome analysis and differential gene expression profiling of wucai (Brassica campestris L.) in response to cold stress

Background

Wucai suffers from low temperature during the growth period, resulting in a decline in yield and poor quality. But the molecular mechanisms of cold tolerance in wucai are still unclear.

Results

According to the phenotypes and physiological indexes, we screened out the cold-tolerant genotype “W18” (named CT) and cold-sensitive genotype “Sw-1” (named CS) in six wucai genotypes. We performed transcriptomic analysis using seedling leaves after 24 h of cold treatment. A total of 3536 and 3887 differentially expressed genes (DEGs) were identified between the low temperature (LT) and control (NT) comparative transcriptome in CT and CS, respectively, with 1690 DEGs specific to CT. The gene ontology (GO) analysis showed that the response to cadmium ion (GO:0,046,686), response to jasmonic acid (GO:0,009,753), and response to wounding (GO:0,009,611) were enriched in CT (LT vs NT). The DEGs were enriched in starch and sucrose metabolism and glutathione metabolism in both groups, and α-linolenic acid metabolism was enriched only in CT (LT vs NT). DEGs in these processes, including glutathione S-transferases (GSTs), 13S lipoxygenase (LOX), and jasmonate ZIM-domain (JAZ), as well as transcription factors (TFs), such as the ethylene-responsive transcription factor 53 (ERF53), basic helix-loop-helix 92 (bHLH92), WRKY53, and WRKY54.We hypothesize that these genes play important roles in the response to cold stress in this species.

Conclusions

Our data for wucai is consistent with previous studies that suggest starch and sucrose metabolism increased the content of osmotic substances, and the glutathione metabolism pathway enhance the active oxygen scavenging. These two pathways may participated in response to cold stress. In addition, the activation of α-linolenic acid metabolism may promote the synthesis of methyl jasmonate (MeJA), which might also play a role in the cold tolerance of wucai.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08311-3.

Transcriptional profiling reveals changes in gene regulation and signaling transduction pathways during temperature stress in wucai (Brassica campestris L.)

Background

Wucai (Brassica campestris L. ssp. chinensis var. rosularis Tsen) is a cold-tolerant plant that is vulnerable to high temperature. This study explored the response mechanism of wucai to low temperature. In this study, wucai seedlings were treated with different temperatures, including low temperature (LT), high temperature (HT), and a control.

Results

According to transcriptomics analysis, the number of differentially expressed genes (DEGs) in HT and LT was 10,702 and 7267, respectively, compared with the control. The key genes associated with the physiological response of wucai to the treatments were analyzed. The Kyoto Encyclopedia of Genes and Genomes and Gene Ontology annotations indicated the importance of the photosynthesis and photosynthetic-antenna protein pathways. We found that a high-temperature environment greatly inhibited the expression of important genes in the photosynthetic pathway (BrLhc superfamily members, PsaD, PsaE, PsaD, PsaD, PsbO, PsbP, PsbQ, PsbR, PsbS, PsbW, PsbY, Psb27, and Psb28), whereas low temperature resulted in the expression of certain key genes (BrLhc superfamily members, Psa F, Psa H, Psb S, Psb H, Psb 28). In addition, the wucai seedlings exhibited better photosynthetic performance under low-temperature conditions than high-temperature conditions.

Conclusions

Based on the above results, we speculate that upon exposure to low temperature, the plants developed higher cold tolerance by upregulating the expression of genes related to photosynthesis. Conversely, high-temperature stress inhibited the expression of pivotal genes and weakened the self-regulating ability of the plants.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-07981-9.

Molecular interplay between phytohormones and geminiviruses: a saga of a never-ending arms race

Geminiviruses can infect a wide range of plant hosts worldwide and have hence become an emerging global agroeconomic threat. The association of these viruses with satellite molecules and highly efficient insect vectors such as whiteflies further prime their devastating impacts. Plants elicit a strong antiviral immune response to restrict the invasion of these destructive pathogens. Phytohormones help plants to mount this response and occupy a key position in combating these biotrophs. These defense hormones not only inhibit geminiviral propagation but also hamper viral transmission by compromising the performance of their insect vectors. Nonetheless, geminiviruses have co-evolved to have a few multitasking virulence factors that readily remodel host cellular machineries to circumvent the phytohormone-mediated manifestation of the immune response. Furthermore, these obligate parasites exploit plant growth hormones to produce a cellular environment permissive for virus replication. In this review, we outline the current understanding of the roles and regulation of phytohormones in geminiviral pathogenesis.

Bioregulators: unlocking their potential role in regulation of the plant oxidative defense system

Plant bioregulators play an important role in managing oxidative stress tolerance in plants. Utilizing their ability in stress sensitive crops through genetic engineering will be a meaningful approach to manage food production under the threat of climate change. Exploitation of the plant defense system against oxidative stress to engineer tolerant plants in the climate change scenario is a sustainable and meaningful strategy. Plant bioregulators (PBRs), which are important biotic factors, are known to play a vital role not only in the development of plants, but also in inducing tolerance in plants against various environmental extremes. These bioregulators include auxins, gibberellins, cytokinins, abscisic acid, brassinosteroids, polyamines, strigolactones, and ascorbic acid and provide protection against the oxidative stress-associated reactive oxygen species through modulation or activation of a plant's antioxidant system. Therefore, exploitation of their functioning and accumulation is of considerable significance for the development of plants more tolerant of harsh environmental conditions in order to tackle the issue of food security under the threat of climate change. Therefore, this review summarizes a new line of evidence that how PBRs act as inducers of oxidative stress resistance in plants and how they could be modulated in transgenic crops via introgression of genes. Reactive oxygen species production during oxidative stress events and their neutralization through an efficient antioxidants system is comprehensively detailed. Further, the use of exogenously applied PBRs in the induction of oxidative stress resistance is discussed. Recent advances in engineering transgenic plants with modified PBR gene expression to exploit the plant defense system against oxidative stress are discussed from an agricultural perspective.

SlARG2 contributes to MeJA-induced defense responses to Botrytis cinerea in tomato fruit

BACKGROUND

Arginase plays key roles in methyl jasmonate (MeJA)-mediated quality maintenance in vegetables and fruits. MeJA treatment induced the Arginase 2 (SlARG2) expression, which is one of the most important encoding genes of arginase. In addition, the treatment with MeJA induced resistance to pathogenic infection in many plants. However, the functions of SlARG2 in MeJA-induced defense to Botrytis cinerea are unclear. In our work, control and SlARG2-silenced tomato fruits (Solanum lycopersicum) were treated with 0.05 mmoL L^-1 MeJA before storage to assay the roles of SlARG2 in MeJA-induced defense responses to Botrytis cinerea.

RESULTS

Our results indicated that MeJA treatment induced both pathogenesis-related gene expression (PR1, PR2a, PR2b and PR3b), and the activity of defense-related enzymes, as well as upregulated arginine metabolism. Compared to control fruits, the treatment with MeJA also induced the activity of arginase, arginine decarboxylase (ADC) and ornithine aminotransferase (OAT), and expression of SlARG2, SlADC, ornithine decarboxylase (SlODC) and SlOAT, and consequently increased the accumulation of arginine, proline, glutamate, putrescine and spermine. However, the induction effects by MeJA were significantly reduced in fruits in which SlARG2 was silenced and severe disease symptoms were observed.

CONCLUSION

MeJA fumigation could inhibit disease development by inducing pathogenesis-related gene expression (PR1, PR2a, PR2b and PR3b) and defense-related enzymes activity, as well as upregulated arginine metabolism. In addition, SlARG2 silencing could inhibit the functions of MeJA in inducing the accumulation of the above substances. Overall, our study provided strong evidence that SlARG2 was essential for MeJA-induced tomato fruit defense responses to Botrytis cinerea. © 2020 Society of Chemical Industry.

Recent advances on the plant manipulation by geminiviruses

As intracellular parasites, viruses co-opt the molecular machinery of the cells they infect in order to multiply and spread, and the extensiveness and effectiveness of this manipulation ultimately determine the outcome of the interaction between virus and host. Members of the Geminiviridae family, causal agents of devastating diseases in crops, encode only a handful of multifunctional, fast-evolving proteins, which efficiently target host proteins to re-wire plant development and physiology and enable replication and spread of the viral genome. In this review, we offer an overview of the different steps in the geminiviral invasion of the host plant, and explore the knowns and unknowns in geminivirus biology.

The improved resistance against gypsy moth in Larix olgensis seedlings exposed to Cd stress association with elemental and chemical defenses

BACKGROUND

Cadmium (Cd), as an environmental pollutant, can endanger various biological and chemical characteristics of plants in multiple aspects. In this study, the effects of Cd contamination or exposure for 30 and 60 days at 1, 2, 4 mg kg^-1 concentrations on the resistance of Larix olgensis seedlings to the gypsy moth (Lymantria dispar) larvae were investigated.

RESULTS

Our results showed that Cd stress did not significantly affect the growth and biomass parameters of the larch seedlings, which might be attributed to the scavenging mechanism of reactive oxygen species (e.g. superoxide dismutase and peroxidase). Regarding the phytochemical defense, we found that Cd stress significantly changed the contents or activities of protease inhibitors (such as trypsin and chymotrypsin inhibitors) and secondary metabolites (tannins and phenolic acids) in L. olgensis seedling needles; however, their response trends varied with Cd exposure concentrations with a significant increase at low concentrations and a significant decrease at high concentrations. Moreover, both chemical and elemental defenses contributed to the resistance of L. olgensis seedlings to the gypsy moth larvae, and their synergistic effects (between toxic elements and organic metabolites) could provide an overall improved defense of L. olgensis seedlings even at low concentrations of single components, resulting in a detrimental effect on the growth of gypsy moth larvae.

CONCLUSION

These findings call for an urgent need to adjust and optimize pest control strategies in heavy metal polluted areas based on the effects of heavy metal stress on woody plant resistance to pest insects. © 2019 Society of Chemical Industry.

Transcriptome analysis reveals a positive effect of brassinosteroids on the photosynthetic capacity of wucai under low temperature

Background

Brassinosteroids (BRs) have a positive effect on many processes during plant growth and development, and in response to various abiotic stressors. Low-temperature (LT) stress constricts the geographic distribution, growth, and development of wucai (Brassica campestris L. ssp. chinensis var. rosularis Tsen). However, there is little information on the global gene expression of BRs under LT stress in wucai. In this study, the molecular roles of 24-epibrassinolide (EBR) after exogenously application, were explored by RNA sequencing under LT conditions.

Results

According to the Gene Ontology (GO) term and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses, photosynthesis was significantly enriched after spraying EBR under LT. The transcripts encoding the photosystem II (PSII) oxygen-evolving enhancer protein, photosystem I (PSI) subunit, light-harvesting chlorophyll protein complexes I and II, and ferredoxin were up-regulated after the application of EBR. Transcripts encoding several key enzymes involved in chlorophyll biosynthesis were also up-regulated, accompanied by significant differences in the contents of 5-aminolevulinic acid (ALA), porphobilinogen (PBG), protoporphyrin IX (Proto IX), Mg-protoporphyrin IX (Mg-proto IX), protochlorophyllide (Pchl), and photosynthetic pigments. Notably, transcriptional and physiological analyses revealed that under LT stress, plant responses to EBR involved a major reorientation of photosynthesis, as well as porphyrin and chlorophyll metabolism.

Conclusion

This study explored the role of EBR as an LT stress tolerance mechanism in wucai. At the transcription level, LT tolerance manifests as an enhancement of photosynthesis, and the amelioration of porphyrin and chlorophyll metabolism.