AtMAPR3 受δ-amino levulinic acid 誘導而表現之機制研究

Abstract

Recombinant AtMAPR3 purified from E. coli has been shown to possess heme binding ability. AtMAPR3 expression is increased by treated with hydrogen peroxide (H2O2) or δ-amino levulinic acid (ALA), the precursor of tetrapyrroles. The ALA-induced AtMAPR3 expression is blocked by dipyridyl (DPD), an inhibitor of ferrochelatase, indicating a possible induction route via heme. To further clarify if the “via heme” route related to the “via H2O2” route, we treated Arabidopsis with ascorbate, a H2O2 scavenger. It was surprised to find that the AtMAPR3 expression was increased by 8-fold after 6 hours treatment. This result suggested that the AtMAPR3 expression was most likely responsive to a reactive oxygen species (ROS) scavenging system. Since ALA is the precursor of several candidates of retrograde signaling molecules, whether AtMAPR3 expression was regulated by retrograde signaling was also studied. The expression of photosynthesis-associated nuclear genes (PhANGs) were monitored in wild-type, AtMAPR3 overexpression mutant (AtMAPR3-OX) and AtMAPR3 knockout mutant (AtMAPR3-KO) with or without ALA treatment. It was interesting that AtMAPR3 showed opposite expression profile to PhANGs in response to the tetrapyrrole perturbation. Further analysis concerning the role of AtMAPR3 in retrograde signaling is needed. A possible role of AtMAPR3 was proposed that it accommodated free heme and the expression of AtMAPR3 was through a ROS scavenging system triggered by a “specific ROS pool”, which was enhanced in this study by ALA treatment.