Map positions of 69 Arabidopsis thaliana genes of all known nuclear encoded constituent polypeptides and various regulatory factors of the photosynthetic membrane: a case study

Landsberg erecta x Columbia F8 recombinant inbred lines of Arabidopsis thal iana, arrayed BAC clones covering most of the genome, and databank sequence information were used to map the positions of 69 genes in the genome of A. thaliana. These genes encode all known constituents of the photosynthetic thylakoid membrane, some regulatory factors involved in its biogenesis, and the RNA polymerases of nuclear origin that operate in chloroplasts and mit ochondria. Designations of novel genes are proposed. The data of these thre e approaches are generally consistent, although ambiguities have been noted for some genome segments and with gene duplications. For thylakoid multi-s ubunit structures, no positional clustering of genes has been found, not ev en for genes encoding different subunits of the same membrane complex. The genes of the lhc superfamily encoding antenna apoproteins and their relativ es are a particularly intriguing example. The lack of positional clustering is consistent with phylogenetically independent gene translocations from t he plastid (endosymbiont) to the nucleus. This raises the basic question of how independently translocated genes which acquired different promoter seq uences and transit peptides were functionally integrated into common signal transduction chains.