Original article Anthocyanin accumulation and changes in CHS and PR-5 gene expression in Arabidopsis thaliana after removal of the inflorescence stem (decapitation) Shaoshan Li a,b , Åke Strid a,* a Department of Natural Sciences, Örebro Life Science Center, Örebro University, 701 82 Örebro, Sweden b School of Life Science, South China Normal University, Guangzhou 510631, China Received 3 January 2005; accepted 10 May 2005 Available online 06 June 2005 Abstract Anthocyanin accumulation occurs in rosette leaves of Arabidopsis thaliana within 8 days after removal of the inflorescence stem. Expres- sion of stress-induced genes CHS and PR-5 was strongly up-regulated by stem removal, and was highest on day 4 after decapitation. These levels were 10 and 5 times higher than in the control, respectively. No obvious difference was found in expression of LHCB, MEB5.2, or PYROA genes following stem removal. We demonstrate that removing the inflorescence stem triggers events in Arabidopsis, including pig- ment accumulation and changes in gene expression of a subset of stress-induced genes, in a tissue distant from the wound site. © 2005 Elsevier SAS. All rights reserved. Keywords: Anthocyanins; Arabidopsis thaliana; Decapitation; Gene expression; Real-time RT-PCR; Wounding 1. Introduction Growth and differentiation of shoot apical meristem are fundamental components of plant physiology, and play impor- tant roles in plant development. It has been known for a long time that the existence of apical buds in dicot plants is respon- sible for apical dominance [11]. Kotova et al. reported changes in phytohormone status in stems and roots after decapitation of pea seedlings. The IAA level in the internodes decreased two to threefold on the second day after decapitation of seed- lings, while the cytokinin level increased 56-fold for zeatin and zeatin riboside [10]. Many of the molecular events involved in decapitation of plants remain unknown. In the present study we examined changes in pigment levels and regulation of stress genes as a result of removing the inflo- rescence stem in Arabidopsis thaliana. It has been reported that anthocyanin accumulation in many plants can be induced by biotic and abiotic stresses, such as UV-B radiation, drought, high or low temperature, and also that gene expression of stress genes is regulated by one or more stresses [3]. For instance, UV-B radiation regulates a large number of genes in plants. These UV-B-regulated genes can be divided into different classes depending on the levels of stress needed to induce expression and on the temporal dependency of induction [3]. These differences in expression pattern imply distinct signal transduction and regulation path- ways for the different classes of genes. Among UV-B regu- lated genes are those encoding chalcone synthase (CHS), pathogenesis-related (PR) protein, PYRO A and MEB5.2. CHS is the first committed enzyme in flavonoid and antho- cyanin biosynthesis. PYRO A is an enzyme involved in syn- thesis of vitamin B 6 [2] as shown in yeasts and fungi. In turn, vitamin B 6 has been shown to participate in detoxification of reactive oxygen species thought to be formed during UV-B irradiation [3]. MEB5.2, a gene encoding a protein of unknown function, is the gene most highly regulated by UV-B radia- tion out of 5000 tested genes [2]. In addition, most photosyn- thetic genes, such as those encoding light-harvesting com- plex proteins (i.e. LHCBs; Ref. [7]), are down-regulated by UV-B. Such a set of molecular markers are therefore infor- mative to use when comparing gene expression stress regu- lation mechanisms. * Corresponding author. Tel.: +46 19 303 603; fax: +46 19 303 566. E-mail address: ake.strid@nat.oru.se (Å. Strid). Plant Physiology and Biochemistry 43 (2005) 521–525 www.elsevier.com/locate/plaphy 0981-9428/$ - see front matter © 2005 Elsevier SAS. All rights reserved. doi:10.1016/j.plaphy.2005.05.004