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Dynamic behaviour of SIMKK, a plant stress-induced mitogen-activated protein kinase kinase and
its downstream target SIMK |
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Jens Müller, Nils Böhm, Heribert Hirt, Diedrik Menzel and Jozef
Šamaj |
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Institute of Cellular and Molecular Botany, University of Bonn, Kirschallee 1, D –
53115 Bonn, Germany |
| *email:
jozef.samaj@uni-bonn.de
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SIMKK, a stress-induced mitogen-activated protein kinase
kinase (MAPKK) is a specific activator of SIMK, but nothing is known about the dynamic behaviour of these two
signalling enzymes in plants. Therefore, we aimed to study dynamic localization changes of SIMKK and SIMK upon
diverse abiotic stresses. Both, transiently or stably expressed CFP/YFP-tagged SIMKK and SIMK have shown
predominantly nuclear localization under unstressed conditions. By contrast, both kinases partially relocated
to the cytoplasm and co-localized on spot-like vesicular structures upon salt and oxidative stress. Other
abiotic stresses, such as heat and wounding, but not the exposure to elicitors (flagellin, chitin,
β-glucan and ergosterol) also caused relocation of SIMKK to cytoplasmic vesicular compartments. Detailed
time-lapse observations revealed that SIMKK was actually recruited to motile endomembraneous organelles (most
likely representing endosomes) upon stress. |
