A specific spectrum of plant and animal miRNAs confer enhanced resistance to virulent pathogens. Plants deficient in miRNA accumulation are hyper-susceptible to non-virulent bacterial pathogens, and virulent bacteria suppress miRNA pathways by means of injected type-III secreted (TTS) proteins. Methods and compositions for modulating the miRNA pathway in plants and animals are disclosed whereby adverse effects on plant and animal development are avoided or minimized.