A MADS-box gene is involved in soybean resistance to multiple Soybean mosaic virus strains

Soybean mosaic virus (SMV) is a member of the genus Potyvirus that extensively impairs global soybean production. The full-length coding sequence of the MADS-box transcription factor GmCAL was cloned from the SMV-resistant soybean cultivar Kefeng 1. SMV-induced expression analysis indicated that GmCAL responded quickly to SMV-SC8 infection in Kefeng 1 but not in NN1138-2. GmCAL was expressed at high levels in flowers and pods but at lower levels in leaves. The gene was localized to the nucleus by subcellular localization assay. Virus-induced gene silencing did not increase the accumulation of SMV in GmCAL-silenced Kefeng 1 plants (with silencing efficiency ∼ 80%) after SC8 inoculation. GmCAL-silencing plants still conferred resistance to SC8 that might be owing to incomplete silencing of genes with lower expression. SMV content decreased significantly in GmCAL-overexpressing NN1138-2 plants after SMV-SC3, SMV-SC7, and SMV-SC8 inoculation in comparison with a vector control, showing that overexpression of GmCAL conferred broad-spectrum resistance to multiple SMV strains. These results confirm that GmCAL, a key regulator but not a specific SC8 resistance gene (Rsc8), is a positive regulatory transcription factor involved in soybean resistance to SMV.