The TyrA family of aromatic-pathway dehydrogenases in phylogenetic context

Table 5 Key to evolutionary events asserted in Figure 6

Group		Evolutionary event(s) proposed
Beta	1	Dispersal of aroQ•pheA > hisH _b> tyrA away from one another and away from gyrA > serC and from cmk > rspA > himD; inversion of aroF with respect to cmk.
	2	Complete dispersal of all nine genes originally in the gyrA/himD linkage group.
	3	Insertion of serA after serC ^a; separation of tyrA and aroF to yield the separated 6-gene unit and 4-gene unit shown.
	4	Expulsion of hisH _bfrom the genome; insertion of 'ORF' after serC.
	5	Fusion of tyrA with aroF.
	6	Loss of hisH _b from genome.
Upper-Gamma	1	Insertion of serA after serC ^a; insertion of aroA _Iα after hisH _b.
	2	Translocation of hisH _band tyrA to other regions, leaving two separated 3-gene units.
	3	Fusion of tyrA with aroF.
	4	Loss of hisH _b.
	5	N-terminal deletion of •aroF domain, and acquisition of new aroF gene (probable LGT).
	6	Separation of cmk > rpsA > himD from aroQ•pheA > tyrA•aroF.
	7	Insertion of 4 unknown genes between gyrA and serC in opposite orientation and separation of gyrA > ORF > ORF > ORF > serC from aroQ•pheA > tyrA•aroF.
	8	Loss of himD; translocation of serC away from gyrA and aroQ•pheA.

^aSince both Nitrosomonas (beta Proteobacteria) and Acidothiobacillus (upper-gamma Proteobacteria) emerge at deep positions in the tree of Fig. 5, an almost equally parsimonius possibility is that the ancestral serA was retained in this syntenic position in these two genera, but was transposed elsewhere shortly after early divergence.

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