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

• Published in: Environmental and experimental botany 2011-11, Vol.73, p.31-41
• Main Authors: Chen, Shiguo, Zhou, Fengyan, Yin, Chunyan, Strasser, Reto Jörg, Yang, Chunlong, Qiang, Sheng
• Format: Article
• Language: English
• Subjects: 3-AIPTA; Biological and medical sciences; Fundamental and applied biological sciences. Psychology; JIP-test; PSII inhibitor; Tetramic acid; The Q B-niche
• ISSN: 0098-8472; 1873-7307
• DOI: 10.1016/j.envexpbot.2011.08.005

▶ 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 Q A by occupying the Q B-binding site. ▶ 3-AIPTA has a different binding behavior during interaction with the Q B-niche. ▶ 3-AIPTA and even tetramic acid families, is a novel photosynthesis inhibitor. 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 Q A on the acceptor side of PSII by competing with Q B for the Q B-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 Q B-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.