Tenuazonic acid, a novel natural PSII inhibitor, impacts on photosynthetic activity by occupying the QB-binding site and inhibiting forward electron flow

Abstract

Tenuazonic acid (TeA), a member of representative natural tetramic acids, is a phytotoxin produced by the fungus Alternaria alternata isolated from diseased Croftonweed (Eupatorium adenophorum). TeA strongly inhibits photosynthesis, especially photosystem II (PSII) activity. Evidence from fast chlorophyll fluorescence induction transients of host plant shows that the most important action site of TeA is that it interrupts electron transport beyond QA, on the acceptor side of PSII, and this is due to its binding at the QB-site. On the basis of competition experiments with [14C]atrazine, it is further confirmed that TeA does not share the same binding environment as atrazine, despite their common action target: The QB-site.