Calcium homeostasis in plant cell nuclei

Introduction 261 Are changes in cytosolic and nuclear calcium (dis)connected? 262 Do isolated nuclei convert stimuli into changes in nucleoplasmic calcium concentrations? 265 Biochemical and cytological components allowing nuclei to be (partially) autonomous in regulating nuclear calcium homeostasis: facts, hypotheses and speculation 268 Control of nuclear activity by calcium 270 Concluding remarks 271 Acknowledgements 271 References 271.In plant cells, calcium-based signaling pathways are involved in a large array of biological processes, including cell division, polarity, growth, development and adaptation to changing biotic and abiotic environmental conditions. Free calcium changes are known to proceed in a nonstereotypical manner and produce a specific signature, which mirrors the nature, strength and frequency of a stimulus. The temporal aspects of calcium signatures are well documented, but their vectorial aspects also have a profound influence on biological output. Here, we will focus on the regulation of calcium homeostasis in the nucleus. We will discuss data and present hypotheses suggesting that, while interacting with other organelles, the nucleus has the potential to generate and regulate calcium signals on its own. New Phytologist (2009) 181: 261-274doi: 10.1111/j.1469-8137.2008.02680.x.