Analysis of lipoxygenase mRNA accumulation in the common bean (Phaseolus vulgaris L.) during development and under stress conditions

Plant lipoxygenases (LOX, EC 1.13.11.12) have been involved in processes su ch as stress responses and development. The levels of these enzymes and the ir corresponding mRNAs are modulated during these processes as web as by di fferent effecters such as jasmonic acid (JA), its methyl eater (MeJA) or ab scisic acid (ABA), A new lipoxygenase (LOX) cDNA clone, PvLOX2, was isolate d from a Phaseolus vulgaris nodule library and used to study the LOX mRNA a ccumulation pattern in some developmental stages and in plants subjected to hormone and stress treatments. In nodules, LOX mRNA reaches a maximum leve l around day 14 to 16 after Rhizobium tropici inoculation, as compared with LOX mRNA present in uninoculated and inoculated roots at the same days. LO X antigen is detected in the nodule parenchyma and in the uninfected cells. During germination, bean LOX transcripts start to accumulate 48 h after im bibition, remains at the same level until 72 h after imbibition and then de clines. In hypocotyl, LOX mRNA is abundant in the growing region and almost absent in the mature region. After water stress or ABA treatment, this mRN A increases in the mature region and decreases in the growing region. In be an seedlings, LOX mRNA is accumulated in response to some types of stresses such as cold and desiccation. Wounding, MeJA or ABA treatment of mature le aves also induces LOX mRNA accumulation. These results indicate that in com mon bean plants LOX is required during development and stress conditions.