Assessment of the Response of Beta Carotene Enhanced Transgenic Soybeans to Soybean Mosaic Virus (SMV)

Beta-carotene, a defense chemical, is synthesized by the carotenoid biosynthesis pathway. In the present study, a transgenic soybean line, with a single copy insertion of phytoene synthase and carotene desaturase genes, having high beta-carotene content was studied for its response to systemically inoculated Soybean mosaic virus (SMV). Beta-carotene-enhanced transgenic soybean showed similar leaf and seed symptoms, viral RNA, and protein expression compared to the non-genetically modified (GM) ‘Kwangan’ control. Total antioxidant contents in the non-GM ‘Kwangan’ line were increased after SMV attack in both leaves and seeds; however, the antioxidant contents in the beta-carotene-enhanced soybean line have no significant changes. In addition, both GM and non-GM soybean were detected increased lipid hydroperoxide concentrations in leaves and seeds after SMV infection, even though they did not reach a statistical significant level. Abscisic acid (ABA) levels in beta-carotene-enhanced transgenic soybean seeds was determined 35-fold increase after SMV infections caused a lower seed germination rate and a higher SMV transmission rate to subsequent generations, compared to those of non-GM ‘Kwangan’. Thus, we concluded that the additional production of beta-carotene did not confer resistance of beta-carotene-enhanced transgenic soybean to SMV infections, but caused mass accumulations of ABA in seeds.