Application of fast chlorophyll a fluorescence kinetics to probe action target of 3-acetyl-5-isopropyltetramic acid

3-Acetyl-5-isopropyltetramic acid (3-AIPTA), an analogue of the phytotoxin tenuazonic acid, is a tetramic acid derivate. It is demonstrated here that 3-AIPTA is a multi-target inhibitor of root and shoot growth as well as photosynthesis. Based on fast chlorophyll fluorescence kinetics, 3-AIPTA blocks electron transport beyond QA on the acceptor side of PSII by competing with QB for the QB-binding site, but does not affect the donor side and the light harvesting function of the PSII antenna. Additionally, higher 3-AIPTA concentration also inhibits the reduction of end acceptors of PSI. Evidences from JIP-test and competitive replacement with [14C]atrazine showed that 3-AIPTA, like tenuazonic acid, does not share the same binding environment with the atrazine-like PSII inhibitors although they possess the common action target of the QB-site. It is deduced that tetramic acid families of natural products, where 3-AIPTA and tenuazonic acid belong to, is a novel inhibitor type of the photosynthetic electron transport chain.

Research highlights▶ Phytotoxin 3-acetyl-5-isopropyltetramic acid (3-AIPTA) is a derivate tetramic acid. ▶ 3-AIPTA is a multi-target inhibitor of root and shoot growth and photosynthesis. ▶ 3-AIPTA interrupts electron flow beyond QA by occupying the QB-binding site. ▶ 3-AIPTA has a different binding behavior during interaction with the QB-niche. ▶ 3-AIPTA and even tetramic acid families, is a novel photosynthesis inhibitor.