The tAPX-NDH interplay: Its control and signalling impact

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Expression of thylakoid-bound ascorbate peroxidase (tAPX) slowly increases for several days in the poststress phase, which leads over time to accumulation of the transcripts and the enzyme to higher levels than the pre-stress ones. Our recent work demonstrated that post-stress tAPX regulation is part of the plant stress memory and of causal importance for specification of future stress signalling. We propose that tAPX dynamically controls initiation of chloroplast-to-nucleus signalling in the thylakoid membrane by competing with plastid NDH (ferredoxin-dependent plastoquinone reductase) for interaction with the donor site of photosystem I.In our future project, we will analyse the control and signalling impact of the tAPX-NDH interplay. We will investigate the distribution of tAPX, of the photosystems, light harvesting complexes and NDH in the thylakoid membrane with respect to tAPX abundance and diurnal tAPX regulation and analyse the micro-environment of tAPX mass-spectrometrically. To investigate the driving forces regulating the tAPX-NDH interplay, we will study tAPX and NDH regulation in a series of differentiating genetic backgrounds. We will extent a recent RNA-Seq study on tAPX-specific gene regulation to differentiate the NDH activity and NDH structural components in tAPX-dependent gene regulation.