Plant Science 148 1999 165 – 174
Expression of the tobacco gene CBP20 in response to developmental stage, wounding, salicylic acid and heavy metals
Go¨tz Hensel, Gotthard Kunze , Irene Kunze
1 Institut fu¨r Pflanzengenetik und Kulturpflanzenforschung
IPK , Corrensstr.
3
, D-
06466
Gatersleben, Germany Received 23 April 1999; received in revised form 6 July 1999; accepted 12 July 1999
Abstract
The pathogenesis-related PR-protein CBP20 which is a basic representative of the group PR-4 is similarly regulated as the basic protein class-I b-1,3-glucanase and class I chitinase of PR-2 and PR-3, respectively. It shows complex hormonal,
developmental and pathogenesis-related regulation. The protein is constitutively accumulated in suspension-cultured cells, in roots and in lower source leaves of healthy tobacco plants, but not in upper, sink leaves near the top of the plant. After spraying the
plants with salicylic acid, the protein CBP20 was also detected in sink leaves, indicating a potential function of salicylic acid in the signal transduction pathway. Synthesis of CBP20 is inducible by heavy metals, especially zinc chloride, which was shown by
Northern and Western blotting. We have demonstrated that the accumulation of mRNA not always resulted in accumulation of the appropriate protein leading to the suggestion that expression of CBP20 is transcriptionally as well as post-transcriptionally
regulated by more than one response pathway. © 1999 Published by Elsevier Science Ireland Ltd. All rights reserved.
Keywords
:
Heavy metal ions; Nicotiana tabacum; Pathogenesis-related protein; Salicylic acid www.elsevier.comlocateplantsci
1. Introduction
Pathogenesis-related PR-proteins of plants are accumulated in response to infections by viruses,
bacteria or fungi for reviews, see [1 – 8]. In addi- tion, there are some members of different PR-
families which have been found to be synthesized after treatments with chemicals such as air pollu-
tants, phytohormones like auxins, cytokinins and ethylene, osmotic stress or salt stress conditions
and others for review, see [9]. Production of PR-proteins has also been shown to be develop-
mentally regulated in healthy plants since high levels of some PR-proteins have been reported in
roots, senescent leaves and during flowering [9].
The PR-protein CBP20 is known as a pathogen- and wound-inducible antifungal protein of 20
kDa firstly purified from tobacco Nicotiana tabacum Samsun NN leaves inoculated with to-
bacco mosaic virus TMV [10]. It belongs to class I PR-4 proteins based on its structural and im-
munological relationship to class II PR-proteins PR-4a and PR-4b of tobacco and PR-2 of tomato
and its intracellular localization [10]. The authors demonstrated its accumulation by TMV, ethephon-
treatment, wounding and UV light-treatment by Northern blotting analysis. But so far it is un-
known, whether the increased transcript levels cause in each case an increased protein level as well.
In this paper, we demonstrate that several envi- ronmental signals and different developmental
stages induce the accumulation of CBP20 mRNA and protein. However, the mRNA level does not
correlate in each case with the appropriate protein level and vice versa. In addition, a correlation
between the levels of transcript and protein caused by heavy metals indicates at least two separate
signal transduction pathways for the induction of CBP20.
Corresponding author. Tel.: + 49-394-825-520; fax: + 49-394- 825-366.
E-mail address
:
kunzegipkgatersleben.de G. Kunze
1
Present address: SunGene GmbH Co. KG aA, Corrensstr. 3, D-06466 Gatersleben, Germany.
0168-945299 - see front matter © 1999 Published by Elsevier Science Ireland Ltd. All rights reserved. PII: S 0 1 6 8 - 9 4 5 2 9 9 0 0 1 3 4 - X
2. Materials and methods
