Abstract
Chloroplast-encoded photosynthesis genes are transcribed by eubacterial-type RNA polymerase named PEP. Standard PEP promoters are analogous to σ70type promoters containing -35 and -10 sequences. The psbD gene encoding the reaction center protein D2 is transcribed from a unique light-responsive PEP promoter (psbD LRP), which is activated by various environmental stresses including high-light, salt and osmotic stresses. The psbD LRP is dependent on an upstream transcription activating element (AAG-box). We mapped the psbD LRPs in several land plants from mosses to angiosperms by primer extension assays. The AAG-box type psbD LRP is conserved among gymnosperms and angiosperms. On the other hand, fern psbD LRP contains a distinct conserved element. It is implicated that two types of psbD LRP have evolved independently from an ancestral promoter. Interestingly, the psbD LRP activity was not regulated by light in gymnosperms and ferns, suggesting that light-dependent psbD transcription might have been emerged during angiosperm evolution.
