The involvement of jasmonates and ethylene in Alternaria alternata f. sp. lycopersici toxin-induced tomato cell death

Abstract

Previous studies have shown that an ethylene (ET)-dependent pathway is involved in the cell death signalling triggered by Alternaria alternata f. sp. lycopersici (AAL) toxin in detached tomato (Solanum lycopersicum) leaves. In this study, the role of jasmonic acid (JA) signalling in programmed cell death (PCD) induced by AAL toxin was analysed using a 35S::prosystemin transgenic line (35S::prosys), a JA-deficient mutant spr2, and a JA-insensitive mutant jai1. The results indicated that JA biosynthesis and signalling play a positive role in the AAL toxin-induced PCD process. In addition, treatment with the exogenous ET action inhibitor silver thiosulphate (STS) greatly suppressed necrotic lesions in 35S::prosys leaves, although 35S::prosys leaflets co-treated with AAL toxin and STS still have a significant high relative conductivity. Application of 1-aminocyclopropane-1-carboxylic acid (ACC) markedly enhanced the sensitivity of spr2 and jai1 mutants to the toxin. However, compared with AAL toxin treatment alone, exogenous application of JA to the ET-insensitive mutant Never ripe (Nr) did not alter AAL toxin-induced cell death. In addition, the reduced ET-mediated gene expression in jai1 leaves was restored by co-treatment with ACC and AAL toxin. Furthermore, JA treatment restored the decreased expression of ET biosynthetic genes but not ET-responsive genes in the Nr mutant compared with the toxin treatment alone. Based on these results, it is proposed that both JA and ET promote the AAL toxin-induced cell death alone, and the JAI1 receptor-dependent JA pathway also acts upstream of ET biosynthesis in AAL toxin-triggered PCD.

Multiple phytohormone signalling pathways modulate susceptibility of tomato plants to Alternaria alternata f. sp. lycopersici

“…Seedlings were grown in a greenhouse, with temperature ranging from 22 to 28 °C (night and day air temperature, respectively) and a 16/6 light/dark cycle. Three weeks after germination, seedlings were transplanted to plastic pots (12cm diameter, 15cm depth) filled with perlite and turfy soil (3:1, v/v), which were watered daily and fertilized weekly with a half-strength Enshi nutrient solution (Zhang et al , 2011). Tomato plants of 7 weeks of age were used in this study.…”

“…For reverse transcription, oligo(dT)18 primers, 10mM dNTP mix, and water were added to 5 µg RNA, following the manufacturer’s protocol (Fermentas, Canada). Quantitative PCR was performed as described previously (Zhang et al , 2011). All experiments were repeated twice, with similar results.…”

Modifications of sphingolipid content affect tolerance to hemibiotrophic and necrotrophic pathogens by modulating plant defense responses in Arabidopsis

“…Coronatine-deficient mutants of Pst DC3000 are reduced in disease-associated necrosis and chlorosis (Brooks et al, 2004(Brooks et al, , 2005. It has been reported that JA is also essential in FB1-and AALinduced cell death (Asai et al, 2000;Zhang et al, 2011). Interestingly, the Atdpl1 mutant is more sensitive to FB1 treatment (Tsegaye et al, 2007).…”

Critical Role of COI1-Dependent Jasmonate Pathway in AAL toxin induced PCD in Tomato Revealed by Comparative Proteomics

“…Several studies showed that JA and ET are closely related to AAL toxin induced PCD11. During AAL toxin induced PCD process in Arabidopsis loh2 mutant (a T-DNA knockout mutant of a homologue of the tomato Asc gene), ET-responsive genes were up-regulated within seven hours, but JA pathway related genes were unchanged, and there was no indication of JA accumulation12.…”