Background: Ethylene plays an important role in the regulation of floral organ development in soybean, and ACC synthase is a rate-limiting enzyme for ethylene biosynthesis. However, whether ACC synthase also regulates floral organ differentiation in soybean remains unknown. To address this, we constructed an RNAi vector to inhibit ACC synthase expression in cotyledonary nodes. Linear DNA cassettes of RNAi-ACS obtained by PCR were used to transform soybean cotyledonary nodes.

Results: One hundred thirty-one of 139 transiently transformed plants acquired herbicide resistance and displayed GUS activities in the new buds. In comparison to untransformed seedling controls, a greater number of flower buds were differentiated at the cotyledonary node; GM-ACS1 mRNA expression levels and ethylene emission in the transformed buds were reduced.

Conclusion: These results indicate that the cotyledonary node transient transformation system may be suitable for stable transformation, and that inhibition of ACC synthase expression may be an effective strategy for promoting floral organ differentiation in soybean.