PP2A was reported to be the most stable reference gene in the viral infection of N. benthamiana (Liu et al., 2012), different organs of G. hirsutum (Artico et al., 2010), and in PEG- and heat-treated samples of Caragana intermedia (Zhu et al., 2013), but was unsatisfactory as a reference gene in C. melo (Kong et al., 2014). This evidence concerns the gene PTPA and viral infectious disease.