Effect of the Anticarsia gemmatalis injury on the lipoxygenases activity from soybean leaves

Abstract

Lipoxygenases (LOX) from soybean leaves submitted to the attack of Anticarsia gemmatalis (Lepdoptera:Noctuidae) were characterized by biochemical and kinetic analyses. A commercial cultivar CAC-1 and three lines derived from this cultivar, which differ for the presence and absence of lipoxygenases and the protease inhibitor KTI, were used for those analyses. The leaf LOX pool showed two pronounced peaks of activity at pH 4.5 and 6.5 and optimum temperature at 25 oC. Plants from all genotypes, submitted to the attack of the insect, showed values of lipoxygenase specific activity higher than the controls in the different pHs and temperatures. Also, LOX pool obtained from leaves exposed to the insect at 6, 12 and 24 h, and at 6, 12 and 48 h, after removal of the insect, had "apparent� KM values lower than those obtained in the respective controls. Our results suggest that the soybean plants respond to the attack of A. gemmatalis by increasing lipoxygenase activity, and that the genetic removal of LOX and KTI from soybean seeds does not interfere with the plant's ability to respond to wound via the LOX pathway.