Abstract
The biogenesis of the major thylakoid protein complexes of the photosynthetic apparatus
requires auxiliary proteins supporting individual assembly steps. Here, we identify a plant
lineage specific gene, CGL160, whose homolog, atp1, co-occurs with ATP synthase subunits
in an operon-like arrangement in many cyanobacteria. Arabidopsis thaliana T-DNA
insertion mutants, which no longer accumulate the nucleus-encoded CGL160 protein, accumulate
less than 25% of wild-type levels of the chloroplast ATP synthase. Severe cosmetic
or growth phenotypes result under either short day or fluctuating light growth conditions, respectively,
but this is ameliorated under long day constant light growth conditions where the
growth, ATP synthase activity and photosynthetic electron transport of the mutants are less
affected. Accumulation of other photosynthetic complexes is largely unaffected in cgl160
mutants, suggesting that CGL160 is a specific assembly or stability factor for the CF1CF0
complex. CGL160 is not found in the mature assembled complex but it does interact specifically
with subunits of ATP synthase, predominantly those in the extrinsic CF1 sub-complex.
We suggest therefore that it may facilitate the assembly of CF1 into the holocomplex.