<i>CmNAC083</i> regulates resistance to <i>Alternaria alternata</i> via reactive oxygen species and jasmonic acid signaling pathways in <i>chrysanthemum morifolium</i>

Chrysanthemum morifolium is an ornamental plant of economic importance. Chrysanthemum black spot is caused by Alternaria fungi. Members of the NAC family regulate plant biological and abiotic stress responses. We screened and confirmed the target gene, CmNAC083, by transcriptome sequencing after inoculation with Alternaria fungi. The CmNAC083 gene was cloned from the chrysanthemum 'Jinba' leaves, and its protein structure was analyzed in the present study. CmNAC083 exhibits transcriptional inhibitory activity, and a tobacco subcellular localization experiment revealed that CmNAC083 is found in the nucleus. Compared with other tissues, CmNAC083 was highly expressed in the stem and bud during the vegetative growth period and in the stems and roots during flowering. Inoculation with Alternaria alternata induced sustained high expression of CmNAC083, reaching its peak at 48 h after infection with the black spot pathogen. Overexpression of CmNAC083 can enhance the resistance of chrysanthemums to black spot disease, and its transient silencing presents a susceptible phenotype. The results of RNA sequencing results revealed that the transcription levels of jasmonic acid (JA) biosynthesis, response signal pathway, and reactive oxygen species (ROS) pathway genes in the CmNAC083 overexpression lines were upregulated compared with those in the wild-type (WT) plants. Furthermore, the overexpressing strains exhibited a higher endogenous JA content than WT after treatment with A. alternata. Overall, CmNAC083 overexpression positively enhances chrysanthemum resistance to black spot disease by regulating A. alternata infection by upregulating the transcription levels of the JA synthesis and ROS pathways.