Abstract The hormones salicylic acid (SA) and jasmonic acid (JA) often act antagonistically in controlling plant defense pathways in response to hemibiotrophs/biotrophs (hemi/biotroph) and herbivores/necrotrophs, respectively. Threonine deaminase (TD) converts threonine to α-ketobutyrate and ammonia as the committed step in isoleucine (Ile) biosynthesis and contributes to JA responses by producing the Ile needed to make the bioactive JA–Ile conjugate. Tomato (Solanum lycopersicum) plants have two TD genes: TD1 and TD2. A defensive role for TD2 against herbivores has been characterized in relation to JA–Ile production. However, it remains unknown whether TD2 is also involved in host defense against bacterial hemi/biotrophic and necrotrophic pathogens. Here, we show that in response to the bacterial pathogen-associated molecular pattern (PAMP) flagellin flg22 peptide, an activator of SA-based defense responses, TD2 activity is compromised, possibly through carboxy-terminal cleavage. TD2 knockdown (KD) plants showed increased resistance to the hemibiotrophic bacterial pathogen Pseudomonas syringae but were more susceptible to the necrotrophic fungal pathogen Botrytis cinerea, suggesting TD2 plays opposite roles in response to hemibiotrophic and necrotrophic pathogens. This TD2 KD plant differential response to different pathogens is consistent with SA- and JA-regulated defense gene expression. flg22-treated TD2 KD plants showed high expression levels of SA-responsive genes, whereas TD2 KD plants treated with the fungal PAMP chitin showed low expression levels of JA-responsive genes. This study indicates TD2 acts negatively in defense against hemibiotrophs and positively against necrotrophs and provides insight into a new TD2 function in the elaborate crosstalk between SA and JA signaling induced by pathogen infection.
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Transcriptome-wide analysis of selenium-responsive genes in hyperaccumulator Stanleya pinnata and nonaccumulator Stanleya elata.
To obtain better insight into the mechanisms of selenium hyperaccumulation in Stanleya pinnata, transcriptome-wide differences in root and shoot gene expression levels were investigated in S. pinnata and related nonaccumulator Stanleya elata grown with or without 20 M selenate. Genes predicted to be involved in sulfate/selenate transport and assimilation or in oxidative stress resistance (glutathione-related genes and peroxidases) were among the most differentially expressed between species; many showed constitutively elevated expression in S. pinnata. A number of defense-related genes predicted to mediate synthesis and signaling of defense hormones jasmonic acid (JA, reported to induce sulfur assimilatory and glutathione biosynthesis genes), salicylic acid (SA) and ethylene were also more expressed in S. pinnata than S. elata. Several upstream signaling genes that upregulate defense hormone synthesis showed higher expression in S. pinnata than S. elata and might trigger these selenium-mediated defense responses. Thus, selenium hyperaccumulation and hypertolerance in S. pinnata may be mediated by constitutively upregulated JA, SA and ethylene-mediated defense systems, associated with elevated expression of genes involved in sulfate/selenate uptake and assimilation or in antioxidant activity. Genes pinpointed in this study may be targets of genetic engineering of plants that may be employed in biofortification or phytoremediation.
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- Award ID(s):
- 1456361
- NSF-PAR ID:
- 10056470
- Date Published:
- Journal Name:
- Plant biotechnology journal
- ISSN:
- 1467-7644
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Background The sugarcane aphid (SCA;
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/doi.org/10.1111/pbi.12897
