PHOTOSYNTHETIC ELECTRON TRANSPORT MEDIATES THE LIGHT-CONTROLLED UP-REGULATION OF EXPRESSION OF METHIONINE SULFOXIDE REDUCTASE A AND B FROM MARINE MACROALGA ULVA FASCIATA

摘要

Methionine (Met) residues of proteins can be oxidized by reactive oxygen species (ROS) with the formation of two epimers of methionine sulfoxide, S-MetSO and R-MetSO, which are reduced back to methionine by methionine sulfoxide reductase A (MSRA) and B (MSRB), respectively. UfMSRA and UfMSRB were cloned from the marine macroalga Ulva fasciata Delile, and the role of retrograde signal in gene expression was studied. Transcripts of UfMSRA and UfMSRB were increased after light exposure with a peak at 1 h. Treatment of photosynthetic electron transport inhibitors, 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (DBMIB), or stigmatellin, promoted the light-activated increase in UfMSRA transcripts, and a PSI electron donor, 2,6-dichlorophenolindophenol (DCPIP), reversed their effects. Increase of UfMSRB transcript by light was inhibited by DCMU and DBMIB treatments, and their effects were not reversed by DCPIP. Stigmatellin treatment did not affect UfMSRB transcripts. Thus, a relatively oxidized state of electron transport downstream from the cytochrome b(6)f (cytb(6)f ) complex is involved in the light up-regulation of UfMSRA gene expression, and a more reduced state of Q(o) of the cytb(6)f complex is required for the light activation of gene expression of UfMSRB.