The Arabidopsis immune regulator SRFR 1 dampens defences against herbivory by S podoptera exigua and parasitism by H eterodera schachtii

Plants have developed diverse mechanisms to fine tune defence responses to different types of enemy. Cross‐regulation between signalling pathways may allow the prioritization of one response over another. Previously, we identified SUPPRESSOR OF rps4‐RLD 1 (SRFR 1) as a negative regulator of ENHANCED DISEASE SUSCEPTIBILITY1 (EDS1)‐dependent effector‐triggered immunity against the bacterial pathogen P seudomonas syringae pv. tomato strain DC3000 expressing avr R ps4. The use of multiple stresses is a powerful tool to further define gene function. Here, we examined whether SRFR 1 also impacts resistance to a herbivorous insect in leaves and to a cyst nematode in roots. Interestingly, srfr1‐1 plants showed increased resistance to herbivory by the beet army worm S podoptera exigua and to parasitism by the cyst nematode H eterodera schachtii compared with the corresponding wild‐type Arabidopsis accession RLD. Using quantitative real‐time PCR (qRT‐PCR) to measure the transcript levels of salicylic acid (SA) and jasmonate/ethylene (JA/ET) pathway genes, we found that enhanced resistance of srfr1‐1 plants to S. exigua correlated with specific upregulation of the MYC2 branch of the JA pathway concurrent with suppression of the SA pathway. In contrast, the greater susceptibility of RLD was accompanied by simultaneously increased transcript levels of SA, JA and JA/ET signalling pathway genes. Surprisingly, mutation of either SRFR 1 or EDS 1 increased resistance to H . schachtii, indicating that the concurrent presence of both wild‐type genes promotes susceptibility. This finding suggests a novel form of resistance in Arabidopsis to the biotrophic pathogen H . schachtii or a root‐specific regulation of the SA pathway by EDS1, and places SRFR 1 at an intersection between multiple defence pathways.