"Photosynthesis-dependent H2O2 transfer from chloroplasts to nuclei provides a high-light signalling mechanism"

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Wednesday 24 April 2019, 11:00 - 12:30


Chloroplasts communicate information by retrograde signalling to nuclei during acclimation to increased light intensities.  Several potential operating signals originating from chloroplasts have been proposed, but it has proved difficult to establish how such signals are transduced to the nuclei to modulate gene expression. One proposed signal is hydrogen peroxide (H2O2) produced by chloroplasts in a light-dependent manner. We used HyPer2, a genetically-encoded fluorescent H2O2 sensor, to show that in photosynthetic Nicotiana benthamiana epidermal cells, exposure to high light (HL) increased H2O2 production in chloroplast stroma, cytosol and nuclei. Critically, over-expression of stromal ascorbate peroxidase (H2O2 scavenger) or treatment with DCMU (photosynthesis inhibitor) attenuated nuclear H2O2 accumulation and HL-responsive gene expression.  In contrast, cytosolic ascorbate peroxidase over-expression had little effect on nuclear H2O2 accumulation and HL-responsive gene expression. This is because the H2O2 is from a sub-population of chloroplasts closely associated with nuclei. Therefore, we have proposed that direct H2O2 transfer from chloroplasts to nuclei, avoiding the cytosol, enables photosynthetic control over gene expression. Further evidence will be presented which begin to test this hypothesis of a spatially-dependent H2O2-mediated retrograde signalling works in other photosynthetic cell types. I shall, if time permits, also discuss thoughts on how onward transduction of a H2O2 signal in the nucleus could be achieved.

Location Jozef Schell Seminar Room
Contact Prof Phil Mullineaux
School of Biological Sciences
University of Essex