Ectopic Overexpression of EuCHIT30.7 Improves Nicotiana tabacum Resistance to Powdery Mildew

Various strains of powdery mildew (PM), a notorious plant fungal disease, are prevalent and pose a significant threat to plant health. To control PM, transgenic technology can be used to cultivate more resistant plant varieties. In the present study, we utilized the rapid amplification of cDNA ends (RACE) technique to clone the full-length cDNA sequence of the EuCHIT30.7 gene to explore plant genes with disease resistance functions. Bioinformatics analysis revealed that this gene belongs to the GH18 family and is classified as a class III chitinase. The EuCHIT30.7 gene is expressed throughout the Eucommia ulmoides plant, with the most abundant expression in male flowers. Subcellular localization analysis indicated that the protein encoded by this gene was detected within both the cell membrane and cytoplasm. Upon PM inoculation, overexpression of EuCHIT30.7 in tobacco plants led to a significantly reduced relative lesion area and a decreased spore count compared to both wild-type and empty vector control plants. Activities of the protective enzymes, namely, peroxidase (POD), superoxide dismutase (SOD), catalase (CAT), and phenylalaninammo-nialyase (PAL), in tobacco plants overexpressing EuCHIT30.7 were significantly greater than those in wild-type and empty vector tobacco plants. Furthermore, the rate of increase in malondialdehyde (MDA) content was significantly lower in tobacco plants expressing EuCHIT30.7 compared to control tobacco plants. In EuCHIT30.7 transgenic tobacco, the expression of pathogen-related protein genes, namely, PR2, PR5, PR1a, PDF1.2, and MLP423, along with the tobacco PM negative regulatory gene, MLO2, were significantly higher compared to control tobacco plants. These findings suggested that EuCHIT30.7 significantly enhances the resistance of tobacco to PM.