Involvement of Calcium/Calmodulin Signaling in Cercosporin Toxin Biosynthesis by Cercosporanicotianae†
AUTOR(ES)
Chung, Kuang-Ren
FONTE
American Society for Microbiology
RESUMO
Cercosporin is a non-host-selective, perylenequinone toxin produced by many phytopathogenic Cercospora species. The involvement of Ca2+/calmodulin (CaM) signaling in cercosporin biosynthesis was investigated by using pharmacological inhibitors. The results suggest that maintaining endogenous Ca2+ homeostasis is required for cercosporin biosynthesis in Cercospora nicotianae. The addition of excess Ca2+ to the medium slightly increased fungal growth but resulted in a reduction in cercosporin production. The addition of Ca2+ chelators [EGTA and 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid] also reduced cercosporin production. Ca2+ channel blockers exhibited a strong inhibition of cercosporin production only at higher concentrations (>2 mM). Cercosporin production was reduced greatly by Ca2+ ionophores (A23187 and ionomycin) and internal Ca2+ blocker [3,4,5-trimethoxybenzoic acid 8-(diethylamino)octyl ester]. Phospholipase C inhibitors (lithium, U73122, and neomycin) led to a concentration-dependent inhibition of cercosporin biosynthesis. Furthermore, the addition of CaM inhibitors (compound 48/80, trifluoperazine, W-7, and chlorpromazine) also markedly reduced cercosporin production. In contrast to W-7, W-5, with less specificity for CaM, led to only minor inhibition of cercosporin production. The inhibitory effects of Ca2+/CaM inhibitors were partially or completely reversed by the addition of external Ca2+. As assessed with Fluo-3/AM (a fluorescent Ca2+ indicator), the Ca2+ content in the cytoplasm decreased significantly when fungal cultures were grown in a medium containing Ca2+/CaM antagonists, confirming the specificity of those Ca2+/CaM antagonists in C. nicotianae. Taken together, the results suggest that Ca2+/CaM signal transduction may play a pivotal role in cercosporin biosynthesis in C. nicotianae.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=143606Documentos Relacionados
- Calcium/Calmodulin Activation of Soybean Glutamate Decarboxylase.
- Hydrogen peroxide homeostasis: Activation of plant catalase by calcium/calmodulin
- Mechanism of calcium/calmodulin inhibition of rod cyclic nucleotide-gated channels
- The effects of weak extremely low frequency magnetic fields on calcium/calmodulin interactions.
- Calcium/calmodulin inhibition of coupled NaCl transport in membrane vesicles from rabbit ileal brush border.