Possible that the means of Chl d synthesis could be completely unrelated to anything familiar in chlorophyll chemistry, it is far more likely that an enzyme has been recruited from related pathways. Major sources of interest are the large pool of proteins orthologous to ``Chl degradation'' and aromatic ring breakage,PNAS February 12, 2008 vol. 105 no. 6GENETICSFig. 2. Phylogenetic relationship of