Construction of an RNAi vector for knockdown of GM-ACS genes in the cotyledonary nodes of soybean

Background: Ethylene plays an important role in the regulation of floral organ development in soybean, and 1-aminocyclopropane-1-carboxylate synthase (ACS) is a rate-limiting enzyme for ethylene biosynthesis. However, whether ACS also regulates floral organ differentiation in soybean remains unknown. To address this, we constructed an RNAi vector to inhibit ACS expression in cotyledonary nodes. Linear DNA cassettes of RNAi-ACS obtained by PCR were used to transform soybean cotyledonary nodes. Results: In total, 131 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 the inhibition of ACS expression may be an effective strategy for promoting floral organ differentiation in soybean.

The effects of ethylene on the HCl-extractability of trace elements during soybean seed germination

Background Ethylene is capable of promoting seed germination in some plant species. Mobilization of metals such as Fe, Cu, Mn, and Zn in mature seeds takes place when seeds are germinating. However, whether ethylene is involved in the regulation of soybean seed germination and metal element mobilization during early seed germination stage remains unknown. In the present study, seeds were treated with ethylene synthesis inhibitor aminoethoxyvinylglycine (AVG) and ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC), and double distilled H2O (ddH(2)0) treatment was used as control. Ethylene emission, ACC synthase (ACS) expression, ACS enzyme activity and Ca, Zn, Mn, Cu and Fe content in hypocotyls were qualified to analyze the relationship between ethylene and mobilization of these elements. Results The results showed that ACS expression, ACS enzyme activity and ethylene emission peaked at 1 and 7 d after sowing. AVG inhibited ethylene production, promoted the hypocotyls length, ACS expression and its activity, concentrations of total and HCl-extractable Zn, and HCl-extractable Fe in hypocotyls, while ACC caused opposite effects. AVG and ACC treatment had no significantly effects on total and HCl-extractable Ca, Cu and HCl-extractable Mn. Total Mn concentration was promoted by AVG at 1, 3, and 5 d significantly, while ACC treatment tended to have no significantly effects on Mn concentration. Conclusion These findings suggested that ethylene is at least partly involved in the regulation of soybean seed germination. Remobilization of Zn and Fe may be negatively regulated by ethylene.