Extracellular DNA induces resistance against Frankliniella occidentalis through callose accumulation.

The plant immune system has evolved to sense and respond to potential threats. When an insect attacks a plant, endogenous molecules called damage-associated molecular patterns (DAMPs) are released into the apoplast, triggering a cascade of intracellular signals. Extracellular DNA (eDNA) is a DAMP signal which activates the plant's immune responses. However, our understanding of whether the detection of eDNA can lessen the damage caused by herbivores is still restricted. Here, we demonstrate that eDNA treatment in Arabidopsis leaves induced plant resistance against the herbivorous insect Frankliniella occidentalis without compromising the plant's growth. The number of leaves, rosette diameter, fresh weight, and other growth-related parameters in eDNA-treated plants was comparable to water-treated plants. Besides, eDNA treatment reduced the feeding symptoms of F. occidentalis on Arabidopsis leaves. We further found that enhanced resistance in eDNA-treated plants was accompanied by callose accumulation in the affected area, and using the callose-deficient mutant pmr4-1, we demonstrated the positive role of callose in eDNA-induced resistance (eDNA-IR). Additionally, the induction in the jasmonic acid (JA)-signaling marker genes LOX2 and AOS, and the higher accumulation of Jasmonyl-isoleucine (JA-Ile) and JA revealed the role of jasmonates in eDNA-IR. Finally, we demonstrated that the JA signaling mediates callose deposition in eDNA-treated plants by using the JA response mutant jar1-1. These results advance our knowledge of the ability of eDNA to trigger plant resistance and the underlying mechanisms involved in eDNA-IR. [ABSTRACT FROM AUTHOR]