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Central Microscopy

 

The plastid genome and signalling

Chromatin remodelling in plastids

Plant cells apart from their nuclear genome possess genomes in plastids and mitochondria. DNA of the organelles is organized in nucleoids which after staining can be visualized by fluorescence microscopy (Figure). In collaboration with the group of H.-P. Mock at IPK Gaterleben we have analysed the proteome of chloroplast nucleoids. Several proteins identified are related to chromatin remodelling factors in the nucleus and might play a role in restructuring of plastid nucleoids (Figure). Some of these possess a SWIB domain. SWIB-1, was shown to be located both in plastids and the nucleus. It is likely that during evolution in plastids originally prokaryotic DNA binding proteins were replaced by nuclear chromatin remodelling factors.


Localisation of AtSWIB-1:GFP fusion protein in chloroplast nucleoids and nucleus in protoplasts isolated from tobacco leaves. As controls PEND:GFP and GFP were visualized.

 

Chloroplast to nucleus signalling

Plant development and in particular leaf senescence is controlled by retrograde signals originating from plastids. Plastids signals inform about the functional state of the organelle. They include reactive oxygen species such as singlet oxygen and hormones such as jasmonic acid and salicylic acid. We identified a protein involved in regulation of senescence associated genes in the nucleus. To our surprise this Whirly1 protein is also located in chloroplasts (Grabowski et al. 2008). Currently we investigate whether and how Whirly1 is involved in communication between plastids and the nucleus.