Quantitative real-time polymerase chain reaction (qRT-PCR) was performed using a FastStart Universal SYBR Green Master kit (Roche Diagnostics, Shanghai, China). qRT-PCR primers (Table 1) were designed from published target sequences and previously reported (Adams et al., 2009) with Primer Premier 7.0 software (Premier Biosoft, Palo Alto, CA, United States). qRT-PCR was performed on a LightCycler480 (Roche Applied Science, Mannheim, Germany), the products of which were purified by using a DNA gel extraction kit (Takara Bio Inc., Tokyo, Japan). For the purposes of assay validation, purified products were cloned into pMD19-T and sequenced to verify correct target amplification.