Cell- and tissue-specific localization and regulation of the epithiospecifier protein in Arabidopsis thaliana
- 397 Downloads
The glucosinolate-myrosinase system found in plants of the order Brassicales is one of the best studied plant defense systems. Hydrolysis of the physiologically inert glucosinolates by hydrolytic enzymes called myrosinases, which only occurs upon tissue disruption, leads to the formation of biologically active compounds. The chemical nature of the hydrolysis products depends on the presence or absence of supplementary proteins, such as epithiospecifier proteins (ESPs). ESPs promote the formation of epithionitriles and simple nitriles at the expense of the corresponding isothiocyanates which are formed through spontaneous rearrangement of the aglucone core structure. While isothiocyanates are toxic to a wide range of organisms, including insects, the ecological significance of nitrile formation and thus the role of ESP in plant-insect interactions is unclear. Here, we identified ESP-expressing cells in various organs and several developmental stages of different Arabidopsis thaliana ecotypes by immunolocalization. In the ecotype Landsberg erecta, ESP was found to be consistently present in the epidermal cells of all aerial parts except the anthers and in S-cells of the stem below the inflorescence. Analyses of ESP expression by quantitative real-time PCR, Western blotting, and ESP activity assays suggest that plants control the outcome of glucosinolate hydrolysis by regulation of ESP at both the transcriptional and the post-transcriptional levels. The localization of ESP in the epidermal cell layers of leaves, stems and reproductive organs supports the hypothesis that this protein has a specific function in defense against herbivores and pathogens.
KeywordsArabidopsis thaliana Epithiospecifier protein Glucosinolates Plant development Regulation
flame ionization detection
quantitative real-time PCR
ribosomal protein 2, large subunit
We thank Andrea Bergner for technical assistance, Michael Reichelt for providing intact glucosinolates, and the Max Planck Society for financial support.
- Andréasson E, Jørgensen LB (2003) Localization of plant myrosinases and glucosinolates. In: Romeo JT (eds) Integrative phytochemistry: from ethnobotany to molecular ecology, recent advances in phytochemistry, vol 37. Elsevier, Amsterdam, pp 79–99Google Scholar
- Fieldsend J, Milford GFJ (1994) Changes in glucosinolates during crop development in single-low and double-low genotypes of winter oilseed rape (Brassica napus). 1. Production and distribution in vegetative tissues and developing pods during development and potential role in the recycling of sulfur within the crop. Ann Appl Biol 124:531–542Google Scholar
- Kliebenstein DJ, Gershenzon J et al (2001a) Comparative quantitative trait loci mapping of aliphatic, indolic and benzylic glucosinolate production in Arabidopsis thaliana leaves and seeds. Genetics 159:359–370Google Scholar
- Matile P (1980) The mustard oil bomb—Compartmentation of the myrosinase system. Biochem Physiol Pflanzen 175:722–731Google Scholar
- Scanlon JT, Willis DE (1985) Calculation of flame ionization detector relative response factors using the effective carbon number concept. J Chromatogr Sci 23:333–340Google Scholar
- Wei X, Roomans GM et al (1981) Localization of glucosinolates in roots of Sinapis alba using X-ray-microanalysis. Scan Electron Micros 481–488Google Scholar
- Wittstock U, Kliebenstein DJ et al (2003) Glucosinolate hydrolysis and its impact on generalist and specialist insect herbivores. In: Romeo JT (eds) Integrative phytochemistry: from ethnobotany to molecular ecology, recent advances in phytochemistry, vol 37. Elsevier, Amsterdam, pp 101–126Google Scholar