Spatial gene expression analysis in tomato hypocotyls suggests cysteine as key precursor of vascular sulfur accumulation implicated in Verticillium dahliae defense

authored by

Katharina Klug, Claudia Hogekamp, André Specht, San Shwe Myint, Dominik Blöink, Helge Küster, Walter J. Horst

Abstract

Verticillium dahliae is a prominent generator of plant vascular wilting disease and sulfur (S)-enhanced defense (SED) mechanisms contribute to its in-planta elimination. The accumulation of S-containing defense compounds (SDCs) including elemental S (S⁰) has been described based on the comparison of two near-isogenic tomato (Solanum lycopersicum) lines differing in fungal susceptibility. To better understand the effect of S nutrition on V. dahliae resistance both lines were supplied with low, optimal or supraoptimal sulfate-S. An absolute quantification demonstrated a most effective fungal elimination due to luxury plant S nutrition. High-pressure liquid chromatography (HPLC) showed a strong regulation of Cys levels and an S-responsive GSH pool rise in the bulk hypocotyl. High-frequency S peak accumulations were detected in vascular bundles of resistant tomato plants after fungal colonization by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). Global transcriptomic analysis suggested that early steps of the primary S metabolism did not promote the SDCs synthesis in the whole hypocotyl as gene expression was downregulated after infection. Enhanced S fertilization mostly alleviated the repressive fungal effect but did not reverse it. Upregulation of glutathione (GSH)-associated genes in bulk hypocotyls but not in vascular bundles indicated a global antioxidative role of GSH. To finally assign the contribution of S metabolism-associated genes to high S⁰ accumulations exclusively found in the resistant tomato line, a spatial gene expression approach was applied. Laser microdissection of infected vascular bundles revealed a switch toward transcription of genes connected with cysteine (Cys) synthesis. The upregulation of LeOASTLp1 suggests a role for Cys as key precursor for local S accumulations (possibly S⁰) in the vascular bundles of the V. dahliae-resistant tomato line.

Organisation(s)

Institute of Plant Nutrition
Section Plant Genomics
Institute of Plant Genetics

External Organisation(s)

Yezin Agricultural University

Type

Article

Journal

Physiologia plantarum

Volume

153

Pages

253-268

No. of pages

16

ISSN

0031-9317

Publication date

01.02.2015

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

Physiology, Genetics, Plant Science, Cell Biology

Electronic version(s)

https://doi.org/10.1111/ppl.12239 (Access: Closed)