The LeATL6-Associated Ubiquitin/Proteasome System May Contribute to Fungal Elicitor-Activated Defense Response via the Jasmonic Acid-Dependent Signaling Pathway in Tomato

Abstract

The expression of LeATL6, an ortholog of Arabidopsis ATL6 that encodes a RING-H2 finger protein, was induced in tomato roots treated with a cell wall protein fraction (CWP) elicitor of the biocontrol agent Pythium oligandrum. The LeATL6 protein was expressed as a fusion protein with a maltose-binding protein (MBP) in Escherichia coli, and it catalyzed the transfer of ubiquitin to the MBP moiety on incubation with ubiquitin, the ubiquitin-activating enzyme E1, and the ubiquitin-conjugating enzyme E2; this indicated that LeATL6 represents ubiquitin ligase E3. LeATL6 expression also was induced by elicitor treatment of jail-1 mutant tomato cells in which the jasmonic acid (JA)-mediated signaling pathway was impaired; however, JA-dependent expression of the basic PR-6 and TPI-1 genes that encode proteinase inhibitor II and I, respectively, was not induced in elicitor-treated jail-1 mutants. Furthermore, transient overexpression of LeATL6 under the control of the Cauliflower mosaic virus 35S promoter induced the basic PR6 and TPI-1 expression in wild tomato but not in the jail-1 mutant. In contrast, LeATL6 overexpression did not activate salicylic acid-responsive acidic PR-1 and PR-2 promoters in wild tomato. These results indicated that elicitor-responsive LeATL6 probably regulates JA-dependent basic PR6 and TPI-1 gene expression in tomato. The LeATL6-associated ubiquitin/proteasome system may contribute to elicitor-activated defense responses via a JA-dependent signaling pathway in plants.

Ubiquitination during Plant Immune Signaling

“…Expression of the tobacco ATL gene AVR9/CF-9-RAPIDLY ELICITED132 (ACRE132) was induced during the defense response triggered following specific recognition of the fungal Avr9 effector by the resistance protein Cf-9 (Durrant et al, 2000). Expression of Arabidopsis ATL2, ATL6, ATL9, LeATL6 (for the tomato [Solanum lycopersicum] ortholog of Arabidopsis ATL6), and rice EL5 was rapidly induced in response to elicitor treatment (Salinas-Mondragón et al, 1999;Takai et al, 2002;Serrano and Guzmán, 2004;Ramonell et al, 2005;Hondo et al, 2007;Berrocal-Lobo et al, 2010). In addition, constitutive expression of ATL2 in Arabidopsis led to induced defense-related gene expression (Serrano and Guzmán, 2004).…”

Temporal Global Expression Data Reveal Known and Novel Salicylate-Impacted Processes and Regulators Mediating Powdery Mildew Growth and Reproduction on Arabidopsis

“…In addition, ATL6 (At3g05200) and ATL6-like (At5g27420) C3HC4-type RING fingers reside in this bin. LeATL6 appears to contribute to fungal elicitor-activated defense responses in tomato (Solanum lycopersicum; Hondo et al, 2007), and both of these Arabidopsis genes exhibit chitin-induced expression (Libault et al, 2007). Chitin is a fungal wall component that is hydrolyzed by plant chitinases, with chitin oligomers inducing plant defense responses.…”

The Cuticle Mutanteca2Modifies Plant Defense Responses to Biotrophic and Necrotrophic Pathogens and Herbivory Insects

“…MAMPS or DAMPs such as chitin, flg22, or cellulose rapidly induce several ERGs named ATLs (A. thaliana lethal) (Guzmán 2012;Hondo et al 2007;Salinas-Mondragón et al 1999;Serrano et al 2006). ATL belongs to a multimembered gene family in A. thaliana and Oryza sativa encoding RING-H2 finger proteins (Guzmán 2012;Hondo et al 2007;Salinas-Mondragón et al 1999;Serrano et al 2006).…”