An Arabidopsis mutant that is resistant to the protoporphyrinogen oxidase inhibitor acifluorfen shows regulatory changes in tetrapyrrole biosynthesis.

Several Arabidopsis mutants of the ecotype Dijon were isolated that show resistance to the herbicide acifluorfen, which inactivates protoporphyrinogen oxidase (PPOX), an enzyme of tetrapyrrole biosynthesis. This enzyme provides protoporphyrin for both Mg chelatase and ferrochelatase at the branchpoint, which leads to chlorophyll and heme, respectively. One of the mutations, aci5-3, displays semidominant inheritance.

Metabolic control of the tetrapyrrole biosynthetic pathway for porphyrin distribution in the barley mutant albostrians.

The barley line albostrians exhibits a severe block in chloroplast development as a result of a mutationally induced lack of plastid ribosomes. White leaves of this mutant contain undifferentiated plastids, possess only traces of chlorophyll (Chl), and are photosynthetically inactive. Chl deficiency, combined with a continuous heme requirement, should lead to drastic changes in the tetrapyrrole metabolism in white versus green leaves.