Pha13 A20 and AN1 domains are involved in the expression of PhaNPR1-dependent and -independent immune gene(s) and virus accumulation.
(A and B) Expression level of Pha13, PhaNPR1, PhaRdR1, PhaGRX, and CymMV accumulation level were analyzed by qRT-PCR of healthy P. aphrodite leaves (A), or CymMV pre-infected P. aphrodite (B) and infiltrated with agrobacterium carrying vector (Vector), overexpression clones of Pha13, or the respective A20 and/or AN1 mutant clones. The RNA level of vector was set to 1. Data represent mean ± SD; n = 3 biological replicates; *, P < 0.05, Student’s t-test compared to vector. PhaUbiquitin 10 was used as an internal control for normalization. (C) A model illustrating SA-induced Pha13 transcriptional and post-translational regulation leading to the activation of immune responsive genes. Virus infection caused accumulation of SA and leads to post-translational modification of NPR1, allowing it to enter into the nucleus for the activation of NPR1-dependent immune responsive genes including PR1 and RdR1. On the other hand, increased SA can also regulate Pha13 at both transcriptional and post-translational level and leads to the expression of NPR1-dependent and independent immune responsive genes including NPR1, RdR1 and GRX for virus resistance.