Cloning and Expression Analysis of SiCDPK4 , a Gene Related to Heterosis in Foxtail Millet [( Setaria italica (L.) P. Beauv.)]

Heterosis, which refers to the superior performance of an F 1 hybrid compared to its parents, has been widely used in crop production to increase grain yield. However, the mechanism responsible for heterosis still remains to be explored. Here, we report involvement of Setaria italica Calcium-Dependent Protein Kinase 4 ( SiCDPK4 ) in yield-related heterosis of foxtail millet ( Setaria italica (L.) P. Beauv.). Transient expression of SiCDPK4 -GFP in foxtail millet protoplasts located SiCDPK4 to the plasma membrane. Analysis of its spatial and temporal expression pattern revealed that SiCDPK4 expressed mainly in leaves, but also in roots and spikes. At the filling stage, significantly higher levels of the SiCDPK4 transcript were observed in the leaves and spikes of hybrids with strong yield heterosis than those with medium and weak heterosis, suggesting that SiCDPK4 is most likely related to yield heterosis in foxtail millet.