Fig. 7

a DEGs involved in apoptosis at 24 hpi by RNAseq analysis of mRNA expression levels in the WT and CD44a^−/−-14del zebrafish larvae infected with E. piscicida. b Validation of DEGs involved in apoptosis at 24 hpi by qRT-PCR. c The effect of zebrafish CD44a deficiency on the early and late apoptosis rates at 6 hpi. d mRNA levels of many genes involved in apoptosis in the WT and CD44a^−/−-14del zebrafish with or without the overexpression of p53 following the E. piscicida infection. The larvae were collected at 24 hpi. e, f Zebrafish larvae microinjected with FLAG, CD44a_tv1 or CD44a_tv2 without or with the treatment of Z-IETD-FMK were collected at the indicated post-infection time points, and homogenates were made for CFU counts. g Larval survival analysis in the WT zebrafish larvae microinjected with FLAG, CD44a_tv1 or CD44a_tv2 without or with the treatment of Z-IETD-FMK (n = 60 for each group). h The effect of Z-IETD-FMK on the CD44a_tv1-mediated apoptosis rates at 6 hpi. i The effect of zebrafish CD44a variants on the casp8 activity. j The effect of pifithrin-μ on the early apoptosis regulated by zebrafish CD44a variants at 6 hpi. k The effect of pifithrin-μ on the late apoptosis regulated by zebrafish CD44a variants at 6 hpi. l The effect of pifithrin-μ on the CD44a_tv1-mediated antibacterial activity. m The effect of pifithrin-μ on the CD44a_tv1-mediated larval survival rate (n = 60 for each group). Data are presented as mean values ± SD (n = 3) and p values by Student’s t test are shown in b–f, h–l. *p < 0.05, **p < 0.01; ns not significant.