Karin Krupinska
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Since end of the eighties, Karin Krupinska’s research focussed on gene expression in plastids of higher plants. Plastid possess DNA that is organized in multiple copies in so-called nucleoids being attached to membranes (Powikrowska et al. 2014) The complex proteome of nucleoids which are also named “transcriptionally active chromosomes” has been elucidated (Melonek et al. 2012, 2016). A further emphasis of her research concerned the regulation of leaf senescence, a recycling process coupled with chlorophyll degradation. A controlled senescence is of pivotal importance for crop productivity (Gregersen et al. 2013). With the aim to identify a regulator of senescence, the group of Karin Krupinska detected the WHIRLY1-protein (Krupinska et al. 2014), that is located in the nucleus as well as in chloroplasts (Grabowski et al. 2008) where it regulates compactness of nucleoids (Krupinska et al. 2014; Oetke et al. 2022).

The WHIRLY1 protein belongs to the small family of multifunctional DNA-binding proteins sharing a whirligig-like quarternary structure. WHIRLIES are specific for angiosperms and are found in all three DNA containing compartments of the cell. While most species possess two WHIRLY proteins, some plants have up to five WHIRLIES. The model plant Arabidopsis thaliana has three WHIRLY-proteins (Krause et al. 2005). While WHIRLY1 and WHIRLY3 are targeted to either chloroplasts or mitochondria (Krause et al. 2005), AtWHIRLY3 is dually targeted to both organelles (Golin et al. 2021).

By its dual localization in chloroplasts and nucleus, WHIRLY1 is an excellent candidate protein for communication between chloroplasts and nucleus. Using plastid transformation, a modified AtWHIRLY1-gene has been transferred into the tobacco plastid genome enabling the plants to synthesize a tagged AtWHIRLY1 protein inside chloroplasts. The detection of the tagged AtWHIRLY1 in the nucleus of these tobacco plants clearly showed that WHIRLY1 can translocate from chloroplasts to the nucleus (Isemer et al. 2012). Investigations with barley plants having a highly reduced level of WHIRLY1 revealed that WHIRLY1 plays an important role in acclimation to environment as well as in development, senescence and stress responses (Kucharewicz et al. 2017; Saeid Nia et al. 2022). The impact of WHIRLY1 on stress resistance likely involves the formation of micro-RNAs (Swida-Barteczka et al. 2018).

Open questions addressed by current research activities and cooperations:

  1. Regulation of the subcellular localization of WHIRLIES. In particular, the translocation of the WHIRLY1-protein from chloroplasts to the nucleus is investigated by the doctoral student Giannina Kunz in collaboration with Prof. Eunsook Park in Laramie, Wyoming, USA. This work is supported by DAAD.

  2. Which sequence motifs of barley WHIRLY1 are required for its positive impact on chloroplast development and stress resistance? To answer this question, the barley why1 knockout mutant has been complemented with mutated HvWHIRLY1 sequences. The plants are characterized by the doctoral student Entela Malkaj in the group of Dr. Götz Hensel at HHU Düsseldorf. The joint project is funded by the DFG:

  3. The impact of HvWHIRLY1 on small RNAs in the nucleus is investigated with the group of Prof. Dr. Zofia Szweykowska-Kulinska in frame of the bilateral partnership of CAU and AMU in Poznan, Poland. The cooperation is supported by DAAD.

  4. The role of dual-targeted AtWHIRLY3 in coordination of energy production by mitochondria and chloroplasts? This question will be investigated by Prof. Dr. Jennifer Selinski at the Institute of Botany of CAU using material and preliminary data established in the group of Karin Krupinska.

  5. Posttranslational modifications of WHIRLY protein of Arabidopsis – impact on subcellular localization and function. This question is investigated by Prof. Dr. Agniezka Ludwikow, AMU Poznan, using material and advice from Karin Krupinska. The research is funded by the National Science Center, Poland.

  6. The impact of WHIRLY proteins on epigenetic processes in the nucleus. Research concerning this question is performed by Prof. Dr. Klaus Humbeck, in Halle, MLU, in frame of RTG2498.