Germination-associated lipoxygenase transcripts persist in maturing soybean plants and are induced by jasmonate

Abstract

Full-length and nearly full-length cDNA clones for the two major lipoxygenase (LOX) transcripts in the axis of germinating soybean ( Glycine max [L.] Merr.) represent transcripts distinct from those of the three seed LOX isozymes. Gene-specific probes revealed that the seedling axis LOX transcripts were absent in developing embryos, while seed LOX-3 transcripts did not accumulate in seedlings or in vegetative tissues. Seedling transcripts appeared in axes between 8 and 16 h after the start of imbihition (seeds germinated 24 h after the start of imbibition) and reached maximal levels at 32 h. One seedling transcript (pTK18) was found in all non-embryonic tissues examined: axes and roots and leaves of two-week plants; the second transcript (pTK11) was also found in vegetative tissues but in reduced levels when compared to pTK18, especially in the leaf. Both transcripts were elevated by methyl jasmonate (MeJA) in the seedling. Thus, gene-specific probes allowed us to monitor the accumulation of two specific LOX transcripts under a variety of developmental and environmental conditions. Their accumulation in the seedling, persistence in vegetative tissues and their deduced consensus signal peptide sequences make them candidates for the MeJA-induced vacuolar vegetative storage protein LOXs. This identification awaits employing gene-specific LOX probes on wounded tissues and those from plants grown under nitrogen excess/deficiency and under water stress.