Arabidopsis thaliana mutants impaired in primary metabolism as tools to study retrograde signaling mechanisms
The Arabidopsis thaliana double mutant (adg1-1/tpt-1) exhibits an impaired export of photoassimilates from the stroma in the light (mutation of the triose phosphate/phosphate translocator [tpt] with a residual TPT activity of 5-10%) combined with a complete lack in starch biosynthesis (mutation of the catalytic subunit of ADPglucose pyrophosphorylase [adg]).
The double mutant is severely compromised in growth and in photosynthetic capacity and has to cope with the absorbed light energy without a significant electron/energy sink (Schneider et al. 2002) It is intended to characterise underlying mechanisms, which are established to counteract and to (at least partially) compensate the combined impairment in triose phosphate export and starch formation to avoid massive photo-destruction. It is likely that the double mutant (adg1-1/tpt-1) as well as both single mutants (adg1-1, tpt-1) and derived transgenic approaches can be used as tools to study mechanisms of retrograde signaling, which coordinate the expression of nuclear and plastid encoded photosynthetic genes.
The focus will be on redox signals deriving from photosynthetic electron transport (i.e. plastoquinone), reactive oxygen species and intermediates of tetrapyrrole metabolism. The involvement of transport proteins of the chloroplast inner envelope membrane in the transfer of putative metabolic signals from the chloroplast to the cytosol (nucleus) will also be addressed.