Differential mRNA degradation of two beta-tubulin isoforms correlates with cytosolic Ca2+ changes in glucan-elicited soybean cells.
Transgenic soybean (Glycine max) culture cells expressing apoaequorin, a Ca2+ indicator, were exposed to glucan fragments derived from Phytophthora sojae or to chitin oligomers. The effects of these elicitors on cytosolic Ca2+ concentrations and on mRNA levels of two beta-tubulin isoforms, tubB1 and tubB2, were investigated. The glucan elicitors, to which the cells are known to react with a biphasic cytosolic Ca2+ increase, induced a down-regulation of the tubB1 mRNA levels while the tubB2 mRNA level remained constant. The decrease of tubB1 mRNA level was observed after 1 hour of glucan treatment. In contrast, chitin oligomers, known to provoke a monophasic Ca2+ increase of short duration, did not affect the tubB1 mRNA level. Pre-incubation with 10 mM 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid, an extracellular Ca2+ chelator, blocked the cytosolic Ca2+ increase as well as the decrease of tubB1 mRNA levels induced by glucan elicitors. Likewise, pre-incubation with 1 mM neomycin, which reduced only the second glucan-induced Ca2+ peak, blocked the decrease of tubB1 mRNA level. Experiments with cordycepin, a transcription inhibitor, indicated that glucan fragments induced the degradation of tubB1 mRNA. In conclusion, the glucan-induced cytosolic Ca2+ changes are correlated with a strong increase in tubB1 mRNA degradation.
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Friedrich Miescher-Institut, P.O. Box 2543, CH-4002 Basel, Switzerland. chantal.ebel@ipw.biol.ethz.ch
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D001483:Base Sequence; D002118:Calcium / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism*; D017931:DNA Primers; D005936:Glucans / Q000378:metabolism*; D006868:Hydrolysis; D030821:Plants, Genetically Modified / Q000378:metabolism; D020033:Protein Isoforms / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism*; D013025:Glycine max / Q000166:cytology / Q000378:metabolism*; D014404:Tubulin / Q000235:genetics*
D017931:DNA Primers; D005936:Glucans; D020033:Protein Isoforms; D012333:RNA, Messenger; D014404:Tubulin; D002118:Calcium