Volatiles Released by the Endophytic Fungus Alternaria alstroemeriae from Vaccinium dunalianum Promote the Growth of Arabidopsis thaliana and Nicotiana benthamiana

The study of volatile organic compounds (VOCs)-mediated plant growth promotion has long focused on various beneficial microbial species. As an important natural source of functional biomolecules, the biological function and potential value of VOCs released by plant pathogenic fungi in regulating plant growth still lack sufficient research, and further exploration is needed. In this study, a phytopathogenic fungus <i>Alternaria alstroemeriae</i> (strain Z84) was isolated from <i>Vaccinium dunalianum</i> for the first time, and the effects of its VOCs on the growth of <i>Arabidopsis thaliana</i> and <i>Nicotiana benthamiana</i> were systematically investigated. The results showed that after Z84 VOCs treatment, multiple phenotypic traits of the two plants were significantly improved, and the chlorophyll content was also markedly increased. Transcriptome analysis showed that a total of 1401 differentially expressed genes (DEGs) were identified in the treated <i>A. thaliana</i>, of which 629 were up-regulated and 772 were down-regulated. KEGG enrichment analysis showed that these DEGs were mainly enriched in photosynthesis-antenna proteins, plant-pathogen interaction, glutathione metabolism, plant hormone signal transduction, flavonoid biosynthesis and photosynthesis-related pathways. Metabolomics analysis revealed that Z84 VOCs treatment significantly changed the metabolic profile of <i>A. thaliana</i>, with the most significant changes in amino acid metabolism-related pathways. It is noteworthy that the plant hormone spectrum of <i>A. thaliana</i> was significantly changed after treatment, and the contents of salicylic acid (SA), abscisic acid (ABA) and gibberellins (GAs) were significantly up-regulated. These results not only demonstrate the potential of Z84-derived VOCs to facilitate plant growth but also provide an important basis for further dissecting the molecular mechanisms of plant-pathogenic fungi interactions.