Interplay between plastid and mitochondrial retrograde signalling pathways

BLANCO N.E.; GUINEA-DIAZ M,; WHELAN, J.; STRAND, Å

Cordoba

Congreso; 16th International Congress on Photobiology; 2014

International Union of Photobiology

Mitochondria and chloroplasts are the main energy producers of the plant cell. These two membrane enclosed endosymbiotic derived organelles depend upon each other for sustaining processes as photosynthesis and mitochondrial respiration. Moreover, they must be able to balance the rates of energy production in response to environmental fluctuations, being necessary a tight regulation of dissipative mechanisms to avoid oxidative damage. For instance, plant mitochondrial respiration protects photosynthesis against photoinhibition by dissipating excess redox equivalents from the chloroplasts. Though it is clear that the activities of mitochondria and plastids need to be coordinated, the nature of this communication is unknown. The regulator of alternative oxidase (rao1) mutant was isolated as a mutant deficient in the induction of ALTERNATIVE OXIDASE 1 (AOX1a) expression in response to the inhibitor of the mitochondrial cytochrome c reductase (complex III), antimycin A [1]. RAO1 encodes the nuclear localized cyclin dependent kinase E1 (CDKE;1). The rao1 mutant demonstrated a genome uncoupled phenotype also inresponse to redox changes in the photosynthetic electron transport chain as well as high light irradiance. Thus, CDKE;1 was shown to regulate both LIGHT HARVESTING COMPLEX B and AOX1a expression in response to retrograde signals [2].To identify the initial source of the signalling events, we analysed the localisation of a kinase interactor of CDKE;1. Through transient expression in N. benthamiana, we observed a distribution of the kinase between mitochondria and nuclei. Moreover, under oxidative conditions, kinase-GFP signal was enriched in nuclei. Similar conditions also led to a change in mitochondria and plastids patterning in the cell. Considered altogether, these observations might indicate a way to facilitate retrograde communication from mitochondria and plastids to nucleus.