Abstract
In higher plants, light and cytokinin co-operatively regulate MGDG synthase (MGD) (Yamaryo et al, PCP, 2003). Although light induces accumulation of the mRNA and subsequent increase in MGDG, MGDG does not accumulate by far-red light (700 nm≤) whereas red light (600 nm≤) can. It indicates that MGDG synthesis requires red light (600-700 nm). MGD is also known to require some reducing agents to preserve its activity so that MGD may require the reducing equivalent generated by photosynthesis. In this report, we analyzed the effect of reducing agents and thioredoxin on MGD activity with recombinant MGD (rMGD) expressed in E. coli. The SH residues of the purified rMGD were oxidized and the effects of reducing agents were analyzed. Consequently, we found that thioredoxin effectively reduced the disulfide bond in MGD. We also analyzed the effect of membrane lipids on MGD activity, and found that PA enhanced rMGD activity most effectively.
