COREGULATION OF SOYBEAN VEGETATIVE STORAGE PROTEIN GENE-EXPRESSION BYMETHYL JASMONATE AND SOLUBLE SUGARS

The soybean vegetative storage protein genes vspA and vspB are highly expressed in developing leaves, stems, flowers, and pods as compared w ith roots, seeds, and mature leaves and stems. In this paper, we repor t that physiological levels of methyl jasmonate (MeJA) and soluble sug ars synergistically stimulate accumulation of vsp mRNAs. Treatment of excised mature soybean (Glycine max Merr. cv Williams) leaves with 0.2 molar sucrose and 10 micromolar MeJA caused a large accumulation of v sp mRNAs, whereas little accumulation occurred when these compounds we re supplied separately. In soybean cell suspension cultures, the syner gistic effect of sucrose and MeJA on the accumulation of vspB mRNA was maximal at 58 millimolar sucrose and was observed with fructose or gl ucose substituted for sucrose. In dark-grown soybean seedlings, the hi ghest levels of vsp mRNAs occurred in the hypocotyl hook, which also c ontained high levels of MeJA and soluble sugars. Lower levels of vsp m RNAs, MeJA, and soluble sugars were found in the cotyledons, roots, an d nongrowing regions of the stem. Wounding of mature soybean leaves in duced a large accumulation of vsp mRNAs when wounded plants were incub ated in the light. Wounded plants kept in the dark or illuminated plan ts sprayed with dichlorophenyldimethylurea, an inhibitor of photosynth etic electron transport, showed a greatly reduced accumulation of vsp mRNAs. The time courses for the accumulation of vsp mRNAs induced by w ounding or sucrose/MeJA treatment were similar. These results strongly suggest that vsp expression is coregulated by endogenous levels of Me JA (or jasmonic acid) and soluble carbohydrate during normal vegetativ e development and in wounded leaves.