A cry for help from leaf to root: above ground insect feeding leads to the recruitment of rhizosphere microbes for plant self-protection against subsequent diverse attacks.

Plants have evolved general and specific defense mechanisms to protect themselves from diverse enemies, including herbivores and pathogens. To maintain fitness in the presence of enemies, plant defense mechanisms are aimed at inducing systemic resistance: in response to the attack of pathogens or herbivores, plants initiate extensive changes in gene expression to activate "systemic acquired resistance" against pathogens and "indirect defense" against herbivores. Recent work revealed that leaf infestation by whiteflies, stimulated systemic defenses against both an airborne pathogen and a soil-borne pathogen, which was confirmed by the detection of the systemic expression of pathogenesis-related genes in response to salicylic acid and jasmonic acid-signaling pathway activation. Further investigation revealed that plants use self protection mechanisms against subsequent herbivore attacks by recruiting beneficial microorganisms called plant growth-promoting rhizobacteria/fungi, which are capable of reducing whitefly populations. Our results provide new evidence that plant-mediated aboveground to belowground communication and vice versa are more common than expected.