Evolutive differentiation between alga- and plant-type plastid terminal oxidase: Study of plastid terminal oxidase PTOX isoforms in Marchantia polymorpha

The liverwort Marchantia polymorpha contains two isoforms of the plastid terminal oxidase (PTOX), an enzyme that catalyzes reduction oxygen to water using plastoquinol as substrate. Phylogenetic analyses showed one isoform, here called MpPTOXa, is closely related occurring in plants and some algae, while other MpPTOXb, Chlamydomonas reinhardtii. Mutants each isoform were created CRISPR/Cas9 technology. While no obvious phenotype was found for these mutants, chlorophyll fluorescence demonstrated plastoquinone pool a higher state both mutants. This visible at level measured dark-adapted material by post illumination rise. These results suggest have redundant function. However, when P700 oxidation re-reduction studied, differences between observed. Furthermore, mutant affected MpPTOXb slight alteration pigment composition, non-photochemical quenching slightly lower electron transport rate through photosystem II. may be explained either enzymatic activities or different attributed preferential involvement PTOX linear cyclic flow.