Linalool Activates Oxidative and Calcium Burst and CAM3-ACA8 Participates in Calcium Recovery in Arabidopsis Leaves

Plants produce linalool to respond to biotic stress, but the linalool-induced early signal remains unclear. In wild-type Arabidopsis, plant resistance to diamondback moth ( ) increased more strongly in a linalool-treated group than in an untreated control group. H O and Ca , two important early signals that participated in biotic stress, burst after being treated with linalool in Arabidopsis mesophyll cells. Linalool treatment increased H O and intracellular calcium concentrations in mesophyll cells, observed using a confocal microscope with laser scanning, and H O signaling functions upstream of Ca signaling by using inhibitors and mutants. Ca efflux was detected using non-invasive micro-test technology (NMT), and Ca efflux was also inhibited by NADPH oxidase inhibitor DPI (diphenyleneiodonium chloride) and in cells of the NADPH oxidase mutant . To restore intracellular calcium levels, Ca -ATPase was activated, and calmodulin 3 (CAM3) participated in Ca -ATPase activation. This result is consistent with the interaction between CAM7 and Ca -ATPase isoform 8 (ACA8). In addition, a yeast two-hybrid assay, firefly luciferase complementation imaging assay, and an in vitro pulldown assay showed that CAM3 interacts with the N-terminus of ACA8, and qRT-PCR showed that some JA-related genes and defense genes expressions were enhanced when treated with linalool in Arabidopsis leaves. This study reveals that linalool enhances H O and intracellular calcium concentrations in Arabidopsis mesophyll cells; CAM3-ACA8 reduces intracellular calcium concentrations, allowing cells to resume their resting state. Additionally, JA-related genes and defense genes' expression may enhance plants' defense when treated with linalool.