CASP9 and infection: qRT-PCR analysis revealed that gcHnf4α overexpression upregulated the mRNA levels of apoptosis-related genes—aif, caspase 3, caspase 8, caspase 9, bax, and bcl-2—during A. salmonicida mono - infection (Fig 3A), indicating potential engagement of both pro- and anti-apoptotic pathways.