The plastid sigma factor SIG5 is involved in the diurnal regulation of the chloroplast gene psbD in the moss Physcomitrella patens

We analyzed the function of a plastid sigma factor, SIG5, by targeted gene disruption in the moss Physcomitrella patens. High-intensity light induced the chloroplast gene psbD in the wild-type strain (WT), whereas this induction was nullified in the PpSig5-disrupted strains (Δ Sig5). Moreover, diurnally regulated changes of psbD transcription showed lowered amplitude in Δ Sig5 than in WT. We concluded that the moss SIG5 mediates multiple layers of signals to intricately regulate psbD transcription.