COMPLEX SPATIAL AND TEMPORAL EXPRESSION OF LIPOXYGENASE GENES DURING PHASEOLUS-VULGARIS (L) DEVELOPMENT

A new member (Loxl) of the lipoxygenase (LOX) gene family in French be an was isolated and its specific expression compared to the general ex pression pattern of related LOX genes. LOX transcripts detected by a F rench bean cDNA LOX probe were generally abundant in young, developing tissues, and LOX protein, detected on immunoblots showed a similar di stribution. Tissue prints showed that cell-specific, locally high amou nts of LOX protein were observed in some tissues, for example in parts of the starch sheath in the hypocotyl and a cell layer in the pericar p. The Loxl gene from Phaseolus vulgaris was shown in genomic Southern s to be present as a single copy per haploid genome. RNase protection studies showed that the gene is active and the transcription start sit e was mapped by cDNA primer extension. RNase protection studies showed that Loxl mRNA was present only in flowers and embryonic primary leav es, in stems and most strongly, in young secondary leaves but not in a ny of the other organs tested (i.e. not in roots, nodules, hypocotyls, cotyledons, older secondary leaves, pericarp or seeds). Loxl gene tra nscripts did not accumulate in leaves in response to methyl jasmonate or pathogen inoculation, even though these treatments caused the accum ulation of other LOX transcripts. Thus, the various lipoxygenase genes are regulated differentially during French bean development and in re sponse to different stress stimuli, and possible functions are discuss ed in view of the specific expression pafterns observed.