Changes in primary metabolism and associated gene expression during host-pathogen interaction in clubroot resistance of Brassica napus
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The role of primary metabolism during Brassica napus - Plasmodiophora brassicae interaction leading to clubroot resistance has not yet been investigated thoroughly. In this study, we investigated some of the primary metabolites and their derivatives as well as expression of the genes involved in their biosynthesis to decipher this host-pathogen interaction. For this, two sets (clubroot resistant and susceptible) of canola lines were inoculated with P . brassicae pathotype 3A to investigate the endogenous levels of primary metabolites at 7-, 14-, and 21-days after inoculation (DAI). The associated pathways were curated, and expression of the selected genes was analyzed using qRT-PCR. Our results suggested the possible involvement of polyamines (spermidine and spermine) in clubroot susceptibility. Some of the amino acids were highly abundant at 7- or 14-DAI in both resistant and susceptible lines; however, glutamine and the amino acid derivative phenylethylamine showed higher endogenous levels in the resistant lines at later stages of infection. Organic acids such as malic, fumaric, succinic, lactic and citric acids were abundant in the susceptible lines. Conversely, the abundance of salicylic acid (SA) and the expression of benzoate/salicylate carboxyl methyltransferase ( BSMT ) were higher in the resistant lines at the secondary stage of infection. A reduced disease severity index and gall size were observed when exogenous SA (1.0 mM) was applied to susceptible B . napus ; this further supported the role of SA in clubroot resistance. In addition, a higher accumulation of fatty acids and significant upregulation of the pathway genes, glycerol-3-phosphate dehydrogenase ( GPD ) and amino alcohol phosphotransferase ( AAPT ) were observed in the resistant lines at 14- and 21-DAI. In contrast, some of the fatty acid derivatives such as phosphatidylcholines represented a lower level in the resistant lines. In conclusion, our findings provided additional insights into the possible involvement of primary metabolites and their derivatives in clubroot resistance.Keywords:
Clubroot
Phenylpropanoid
Jasmonic acid
Abstract Leaf trichomes protect plants from attack by insect herbivores and are often induced following damage. Hormonal regulation of this plant induction response has not been previously studied. In a series of experiments, we addressed the effects of artificial damage, jasmonic acid, salicylic acid, and gibberellin on induction of trichomes in Arabidopsis. Artificial damage and jasmonic acid caused significant increases in trichome production of leaves. The jar1-1 mutant exhibited normal trichome induction following treatment with jasmonic acid, suggesting that adenylation of jasmonic acid is not necessary. Salicylic acid had a negative effect on trichome production and consistently reduced the effect of jasmonic acid, suggesting negative cross-talk between the jasmonate and salicylate-dependent defense pathways. Interestingly, the effect of salicylic acid persisted in the nim1-1 mutant, suggesting that the Npr1/Nim1 gene is not downstream of salicylic acid in the negative regulation of trichome production. Last, we found that gibberellin and jasmonic acid had a synergistic effect on the induction of trichomes, suggesting important interactions between these two compounds.
Jasmonic acid
Trichome
Jasmonate
Gibberellic acid
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Salicylic acid and jasmonic acid play an important role in plants coping with abiotic stresses. An experiment was conducted to examine the effect of salicylic acid and jasmonic acid on wheat under drought. Seeds were primed with jasmonic acid (100µM) and salicylic acid (10 Mm). Water stress was applied by withholding water and each treatment was replicated three times with a factorial block design. Application of Salicylic acid and Jasmonic acid mitigated drought effects in wheat. Results revealed that 100µM Jasmonic acid was more effective than 10 mM SA. Drought decreased germination by 26%, whereas application of Jasmonic acid and Salicylic acid ameliorated stress with the increase of germination by 27% and 21%, respectively. An increase in the shoot length of 23% and 20% was observed with Jasmonic acid and Salicylic acid, under drought conditions. The increase in water potential was 60% and 47% with JA and SA while the increase in proline and soluble sugar was 14% and 25% respectively. The application of Jasmonic acid and Salicylic acid has a potential to enhance the growth of wheat plants under drought.
Jasmonic acid
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Jasmonic acid
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Abstract To investigate the regulation of hydrogen peroxide (H2O2) in SA- and JA-dependent systemic defense pathways in tomato seedlings damaged by cotton bollworm. The lower two leaves of four-leaf tomato plant seedlings were treated with cotton bollworms. The upper leaves were then removed at various time points and assessed for systemic changes in H2O2 levels, enzyme activity and defense-related genes expression. Wild-type seedlings, def-5 mutant seedlings (deficient in JA accumulation) and transgenic nahG seedlings(deficient in SA content) were constructed at four-leaf stage. Wild-type plants were further treated with dimethylthiourea (DMTU) and 2,5-dihydroxycinnamic acid methyl ester (DHC). Bollworm feeding in the lower leaves induced rapid systemic accumulation of H2O2 in the upper leaves. H2O2 accumulation further increased activities for SA- and JA-dependent enzymes including proteinase inhibitors (PIs), pathogenesis-related gene 1 (PR-1), cathepsin D inhibitor (CDI), β-1,3-glucanse (BGL) and polyphenol oxidase (PPO). Furthermore, H2O2 accumulation enhanced mRNA expression of BGL-2, PR-1, PI, CDI and PPO genes. Suppression of H2O2 accumulation using H2O2 scavengers substantially diminished these effects. mRNA expression of PR-1 was not induced in transgenic nahG plants. SA- and JA-dependent signaling pathways are involved in the tomato systemic defense responses to herbivores, and that H2O2 generation is required for both systemic pathways.
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Peroxide
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Phytohormones are not only instrumental in regulating developmental processes in plants but also play important roles for the plant's responses to biotic and abiotic stresses. In particular, abscisic acid, ethylene, jasmonic acid, and salicylic acid have been shown to possess crucial functions in mediating or orchestrating stress responses in plants. Here, we review the role of salicylic acid and jasmonic acid in pathogen defence responses with special emphasis on their function in the solanaceous plant potato.
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Biotic stress
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Jasmonic acid
Signalling
Systemic Acquired Resistance
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Jasmonic acid
Systemic Acquired Resistance
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Plants have evolved powerful immune systems to recognize pathogens and avoid invasions, but the genetic basis of plant susceptibility is less well-studied, especially to oomycetes, which cause disastrous diseases in many ornamental plants and food crops. In this research, we identified a negative regulator of plant immunity to the oomycete Phytophthora parasitica, AtRTP5 (Arabidopsis thaliana Resistant to Phytophthora 5), which encodes a WD40 repeat domain-containing protein. The AtRTP5 protein, which was tagged with green fluorescent protein (GFP), is localized in the nucleus and plasma membrane. Both the A. thaliana T-DNA insertion rtp5 mutants and the Nicotiana benthamiana RTP5 (NbRTP5) silencing plants showed enhanced resistance to P. parasitica, while overexpression of AtRTP5 rendered plants more susceptible. The transcriptomic analysis showed that mutation of AtRTP5 suppressed the biosynthesis of endogenous jasmonic acid (JA) and JA-dependent responses. In contrast, salicylic acid (SA) biosynthesis and SA-dependent responses were activated in the T-DNA insertion mutant rtp5-3. These results show that AtRTP5 acts as a conserved negative regulator of plant immunity to Phytophthora pathogens by interfering with JA and SA signalling pathways.
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Oomycete
Pseudomonas syringae
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Genetic screen
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