In addition, we also found that the expression of some genes in the SA-related defence signalling pathway was inhibited in the early infection period of ‘Tolerant 1’ and ‘Tolerant 2’, and this inhibition mostly occurred at 6 hpi and 2 hpi, suggesting that E4 could also interfere with the defence responses of poplars with tolerance to E4, which was reflected in the decrease in the expression of multiple PR genes at 2 hpi or 6 hpi. Here, TMEM37 is linked to infection.