An unexpected role for tomato threonine deaminase 2 in host defense against bacterial infection
An unexpected role for tomato threonine deaminase 2 in host defense against bacterial infection
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DOI：
10.1093/plphys/kiac584
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发表时间：
2022-12-19
期刊：
影响因子：
7.4
通讯作者：
Devarenne，Timothy P.
中科院分区：
文献类型：
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作者：
Yeo，In-Cheol;de Azevedo Manhaes，Ana Marcia Escocard;Devarenne，Timothy P.
激素水杨酸(SA)和茉莉酸(JA)分别对半营养生物/生物营养生物(半/生物营养生物)和草食/坏死营养生物起到拮抗作用，控制植物的防御途径。苏氨酸脱氨酶(TD)将苏氨酸转化为异亮氨酸(α)酮丁酸酯和氨，作为异亮氨酸(ILE)生物合成的关键步骤，并通过产生使具有生物活性的JA-ILE偶联所需的ILE来促进JA的响应。番茄(Solanum Lycopsicum)植物有两个TD基因：TD1和TD2。TD2对食草动物的防御作用已被描述为与JA-Ile生产有关。然而，目前尚不清楚TD2是否也参与了宿主对细菌半营养性/生物营养性和坏死性病原体的防御。在这里，我们表明，作为基于SA的防御反应的激活剂，细菌病原体相关分子模式(PAMP)鞭毛蛋白flg22肽的反应，TD2的活性受到损害，可能是通过羧基末端切割。TD2基因敲除(KD)植物对半生物营养性细菌病原菌丁香假单胞菌表现出更强的抗性，但对坏死性真菌病原菌更敏感，这表明TD2在对半生物营养型和坏死型营养型病原菌的反应中扮演相反的角色。这种TD2KD植物对不同病原菌的差异反应与SA和JA调控的防御基因表达一致。FLG22处理的TD2KD植株表现出高水平的SA反应基因表达，而真菌PAMP甲壳素处理的TD2KD植株表现出低水平的JA反应基因表达。这项研究表明，TD2对半生物营养体的防御是负的，对坏血细胞的防御是正的，这为TD2在病原体感染诱导的SA和JA信号之间复杂的串扰中发挥新的功能提供了新的见解。
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 twoTDgenes:TD1andTD2. 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.TD2knockdown (KD) plants showed increased resistance to the hemibiotrophic bacterial pathogenPseudomonas syringaebut were more susceptible to the necrotrophic fungal pathogenBotrytis cinerea, suggesting TD2 plays opposite roles in response to hemibiotrophic and necrotrophic pathogens. ThisTD2KD plant differential response to different pathogens is consistent with SA- and JA-regulated defense gene expression. flg22-treatedTD2KD plants showed high expression levels of SA-responsive genes, whereasTD2KD 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.