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Plant Physiol

Title:		An unexpected role for tomato threonine deaminase 2 in host defense against bacterial infection
Author(s):		Yeo IC; de Azevedo Manhaes AME; Liu J; Avila J; He P; Devarenne TP;
Address:		"Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843, USA"
Journal Title:		Plant Physiol
Year:		2023
Volume:		192
Issue:		1
Page Number:		527 - 545
DOI:		10.1093/plphys/kiac584
ISSN/ISBN:		1532-2548 (Electronic) 0032-0889 (Print) 0032-0889 (Linking)
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 alpha-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"
Keywords:		*Solanum lycopersicum/genetics Threonine Dehydratase/genetics/metabolism Cyclopentanes/pharmacology/metabolism Oxylipins/pharmacology/metabolism *Bacterial Infections Salicylic Acid/pharmacology/metabolism Plant Diseases/microbiology Gene Expression Regul;
Notes:		"MedlineYeo, In-Cheol de Azevedo Manhaes, Ana Marcia Escocard Liu, Jun Avila, Julian He, Ping Devarenne, Timothy P eng Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, Non-P.H.S. 2022/12/20 Plant Physiol. 2023 May 2; 192(1):527-545. doi: 10.1093/plphys/kiac584"