Jasmonate ZIM-Domain (JAZ) Protein Regulates Host and Nonhost Pathogen-Induced Cell Death in Tomato and <i>Nicotiana benthamiana</i>

<div><p>The nonhost-specific phytotoxin coronatine (COR) produced by several pathovars of <i>Pseudomonas syringae</i> functions as a jasmonic acid-isoleucine (JA-Ile) mimic and contributes to disease development by suppressing plant defense responses and inducing reactive oxygen species in chloroplast. It has been shown that the F-box protein CORONATINE INSENSITIVE 1 (COI1) is the receptor for COR and JA-Ile. JASMONATE ZIM DOMAIN (JAZ) proteins act as negative regulators for JA signaling in <i>Arabidopsis</i>. However, the physiological significance of JAZ proteins in <i>P. syringae</i> disease development and nonhost pathogen-induced hypersensitive response (HR) cell death is not completely understood. In this study, we identified <i>JAZ</i> genes from tomato, a host plant for <i>P. syringae</i> pv. <i>tomato</i> DC3000 (<i>Pst</i> DC3000), and examined their expression profiles in response to COR and pathogens. Most <i>JAZ</i> genes were induced by COR treatment or inoculation with COR-producing <i>Pst</i> DC3000, but not by the COR-defective mutant DB29. Tomato SlJAZ2, SlJAZ6 and SlJAZ7 interacted with SlCOI1 in a COR-dependent manner. Using virus-induced gene silencing (VIGS), we demonstrated that SlJAZ2, SlJAZ6 and SlJAZ7 have no effect on COR-induced chlorosis in tomato and <i>Nicotiana benthamiana</i>. However, <i>SlJAZ2</i>-, <i>SlJAZ6</i>- and <i>SlJAZ7</i>-silenced tomato plants showed enhanced disease-associated cell death to <i>Pst</i> DC3000. Furthermore, we found delayed HR cell death in response to the nonhost pathogen <i>Pst</i> T1 or a pathogen-associated molecular pattern (PAMP), INF1, in <i>SlJAZ2</i>- and <i>SlJAZ6</i>-silenced <i>N. benthamiana</i>. These results suggest that tomato JAZ proteins regulate the progression of cell death during host and nonhost interactions.</p>