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1.
Jyothilakshmi Vadassery Stefanie Ranf Corinna Drzewiecki Axel Mithöfer Christian Mazars Dierk Scheel Justin Lee Ralf Oelmüller 《The Plant journal : for cell and molecular biology》2009,59(2):193-206
Calcium (Ca2+), as a second messenger, is crucial for signal transduction processes during many biotic interactions. We demonstrate that cellular [Ca2+] elevations are early events in the interaction between the plant growth‐promoting fungus Piriformospora indica and Arabidopsis thaliana. A cell wall extract (CWE) from the fungus promotes the growth of wild‐type seedlings but not of seedlings from P. indica‐insensitive mutants. The extract and the fungus also induce a similar set of genes in Arabidopsis roots, among them genes with Ca2+ signalling‐related functions. The CWE induces a transient cytosolic Ca2+ ([Ca2+]cyt) elevation in the roots of Arabidopsis and tobacco (Nicotiana tabacum) plants, as well as in BY‐2 suspension cultures expressing the Ca2+ bioluminescent indicator aequorin. Nuclear Ca2+ transients were also observed in tobacco BY‐2 cells. The Ca2+ response was more pronounced in roots than in shoots and involved Ca2+ uptake from the extracellular space as revealed by inhibitor studies. Inhibition of the Ca2+ response by staurosporine and the refractory nature of the Ca2+ elevation suggest that a receptor may be involved. The CWE does not stimulate H2O2 production and the activation of defence gene expression, although it led to phosphorylation of mitogen‐activated protein kinases (MAPKs) in a Ca2+‐dependent manner. The involvement of MAPK6 in the mutualistic interaction was shown for an mpk6 line, which did not respond to P. indica. Thus, Ca2+ is likely to be an early signalling component in the mutualistic interaction between P. indica and Arabidopsis or tobacco. 相似文献
2.
ASF-2: a factor that binds to the cauliflower mosaic virus 35S promoter and a conserved GATA motif in Cab promoters. 总被引:30,自引:13,他引:30 下载免费PDF全文
We have used nuclear extracts prepared from tobacco leaf tissue to characterize a factor binding site, designated as-2 (activating sequence-2), at the -100 region of the cauliflower mosaic virus 35S promoter. The activity of this factor, called ASF-2 (activating sequence factor-2), is not detected in tobacco root extracts. as-2 includes two GT motifs with sequence homology to the SV40 enhancer core A element and the Box II element of pea rbcS. Nevertheless, oligomers of these sequence elements do not compete for ASF-2 binding in gel retardation assays, indicating that the GT motifs may not be involved. Methylation interference studies identify two guanines (G93 and G98) that are required for interaction with ASF-2. Sequences surrounding these two critical guanines display homologies to a GATA repeat conserved among several light-responsive promoters. One such sequence from a petunia Cab promoter is able to compete with as-2 for factor binding. In transgenic plants, a tetramer of as-2 is able to confer leaf expression when fused 5' to the -90 derivative of the 35S promoter. The expression is not dependent on light and, thus, the as-2 tetramer does not function as a light-responsive element in this context. Histochemical localization of the reporter gene product suggests that the as-2 tetramer directs expression in trichomes, vascular elements, and epidermal and mesophyll cells. 相似文献