Molecular characterization of L2 lipoxygenase from maize embryos.

We investigated the expression and accumulation pattern of lipoxygenase isoforms throughout the maize plant life. Two forms of lipoxygenase L1 and L2 have been identified as acidic proteins of 100 kDa (pI 6.4) and 90 kDa (pI 5.5-5.7) which accumulate in dry embryos and in various organs of maize seedlings. In young embryos, only the L2 form was detected and accumulation of L2 mRNA decreased during embryo development. Identification of lipoxygenases from in vivo and in vitro synthesized proteins indicates that similar levels of both L1 and L2 forms accumulated during treatment with abscisic acid, (ABA) gibberellic acid (GA3) and jasmonic acid (JA). However, differences in the activity of both enzymes were detected. By using an antiserum directed against purified L2 we isolated and characterized a partial cDNA clone of maize embryos encoding a lipoxygenase. The deduced amino acid sequence of L2 cDNA shares 78% identity with the rice L2 protein, and 51-56% identity with lipoxygenases from the dicotyledonous plants soybean and Arabidopsis. DNA blot analysis indicated that maize contains a family of lipoxygenase genes which are presently being characterized.