A CRISPR/Cas9 mediated 53 kb deletion of the NRC4 gene cluster of tomato does not affect bacterial flagellin-triggered immunity

Plants utilise cell surface pattern recognition receptors (PRRs) and intracellular nucleotide-binding domain leucine-rich repeat containing receptors (NLRs) to fend off invading pathogens. Although PRR- and NLR-triggered immunity are generally thought to activate distinct pathways, they can induce similar outputs. However, whether these two pathways converge at some point to potentiate and strengthen the immune response remains unclear. For instance, the extent to which the tomato NLR helper NRC4 is implicated in response to the bacterial flagellin peptide flg22 needs to be elucidated. One challenge is that the tomato NRC4 gene cluster consists of three paralogues and the related NRC5 gene. Here, we took advantage of the CRISPR/Cas9 system to generate a tomato mutant with a 53 Kb deletion that encompasses the four NRC genes. Although this mutant failed to respond to the NRC4-dependent NLR Rpi-blb2, it remained unaltered in flg22-induced responses. We conclude that the NRC4 genes are not essential for flg22-induced responses in tomato.