Synergistic control of chloroplast biogenesis byMYB-relatedandGolden2-liketranscription factors

Abstract Chloroplast biogenesis is dependent on master regulators from the Golden2-like (GLK) family of transcription factors, but higher order glk mutants contain residual chlorophyll and therefore other proteins must also be involved. Here we identify MYB-related transcription factors as regulators of chloroplast biogenesis in the liverwort Marchantia polymorpha and angiosperm Arabidopsis thaliana . In both species, double mutant alleles in MYB-Related genes show very limited chloroplast development and photosynthesis gene expression is perturbed to a greater extent than mutants of GLK . In M. polymorpha MYB-related genes act upstream of GLK , while in A. thaliana this relationship has been rewired. In both species, genes encoding enzymes of chlorophyll biosynthesis are controlled by both MYB-related and GLK proteins whilst those allowing CO 2 fixation, photorespiration as well as photosystem assembly and repair require the MYB-related proteins. Thus, MYB-related and GLK genes have overlapping as well as distinct targets. We conclude that MYB-related transcription factors act with GLK to orchestrate chloroplast development in land plants.