Selective growth suppression of five annual plant species by chalcone and naringenin correlates with the total amount of 4-coumarate: coenzyme A ligase.

The 4-coumarate: coenzyme A ligase (4CL) is one of the key enzymes in the biosynthesis of lignin monomers. It has been demonstrated that the 4CL is a new potential target site for developing effective plant growth inhibitors. Although previous studies demonstrate that chalcone and naringenin differentially suppress the growth of several annual plant species, we show here that the compounds can inhibit the 4CL enzyme activity in the plants. The enzyme was extracted and partially purified from the leaf tissues of two tolerant plants (wheat and soybean) and three susceptible plants (tomato, barnyard grass, and common chickweed). A maximal 29-fold purification of the enzyme, with a yield of 32% (tomato), was achieved by a six-step procedure, including anion-exchange column chromatography. Naringenin strongly inhibited the 4CL specific activity in wheat, soybean and barnyard grass, whereas chalcone showed the highest inhibitory effect in common chickweed. A good correlation was observed between the level of growth suppression by the compounds and the total 4CL amount in the plants. These results suggest that the inhibitor treatment at the same concentration could not inactivate the entire 4CL enzyme produced in the tolerant plants. Taken together, these results highlight the possibility of the 4CL as a new action site of growth suppression. [ABSTRACT FROM AUTHOR]