RNA m⁶A Methylation Suppresses Insect Juvenile Hormone Degradation to Minimize Fitness Costs in Response to A Pathogenic Attack

Bioinsecticides and transgenic crops based on the bacterial pathogen Bacillus thuringiensis (Bt) can effectively control diverse agricultural insect pests, nevertheless, the evolution of resistance without obvious fitness costs has seriously eroded the sustainable use of these Bt products. Recently, it has been discovered that an increased titer of juvenile hormone (JH) favors an insect host (Plutella xylostella) to enhance fitness whilst resisting the Bt pathogen, however, the underlying regulatory mechanisms of the increased JH titer are obscure. Here, the involvement of N-6-methyladenosine (m(6)A) RNA modification in modulating the availability of JH in this process is defined. Specifically, it is found that two m(6)A methyltransferase subunit genes, PxMettl3 and PxMettl14, repress the expression of a key JH-degrading enzyme JH esterase (JHE) to induce an increased JH titer, mitigating the fitness costs associated with a robust defense against the Bt pathogen. This study identifies an as-yet uncharacterized m(6)A-mediated epigenetic regulator of insect hormones for maintaining fitness during pathogen defense and unveils an emerging Bt resistance-related m(6)A methylation atlas in insects, which further expands the functional landscape of m(6)A modification and showcases the pivotal role of epigenetic regulation in host-pathogen interactions.