NpPP2-B10, an F-Box-Nictaba Gene, Promotes Plant Growth and Resistance to Black Shank Disease Incited by Phytophthora nicotianae in Nicotiana tabacum

Overexpression of the Eucommia ulmoides chitinase EuCHIT73.88 gene improves tobacco disease resistance

Black shank disease is the main disease affecting tobacco crops worldwide, and the main impacted by the disease are the stem base and root. At present, transgenic technology is an effective method to improve plant disease resistance through transgenic technology. In this study, the EuCHIT73.88 gene was cloned from Eucommia ulmoides Oliver (E. ulmoides) by using RT-PCR. The full length of the gene was 897 bp, encoding 298 amino acid residues. An overexpression vector of from the EuCHIT73.88 gene driven by the 35S promoter was constructed and transferred into tobacco plants via transgenic technology. After inoculation with the black shank pathogen, the number of visible lesions on the stems and leaves of the transgenic tobacco variety EuCHIT73.88 was significantly shorter than that on the stems and leaves of the of wild type (WT) and empty vector (EV) plants, and the lesion area was significantly smaller than on the stems and leaves of the WT and EV plants. With increasing inoculation time, introduction of the WT and EV vectors was obviously lethal, whereas transgenic tobacco only exhibited wilted characteristics, and the stems were black, which indicated that the EuCHIT73.88 gene could improve the resistance of tobacco to black shank disease. Furthermore, the activity of protective enzymes and the gene expression of resistance-related proteins were measured. The results showed that compared with those of the WT and EV plants, the CAT and POD activities of the TP tobacco plants were greater, peaking at 72 h at concentrations of 446.87 U/g and 4562.24 U/g, which were 1.63 and 1.61 times greater than those of the WT and EV plants, respectively. This indicated that CAT and POD may be involved in the process of disease resistance of in the transgenic plants. The MDA content of the transgenic tobacco plants was significantly lower than that of the WT and EV plants with increasing EuCHIT73.88 expression, thus indicating that the overexpression of the transgenic EuCHIT73.88 gene could alleviate the levels of lipid peroxidation and reduce the damage to plant cell membranes. The expression of disease-related protein genes (PR2, PR5, PR1a, PDF1.2 and MLP423) was significantly greater in the EuCHIT73.88 ransgenic tobacco than in the WT and EV-transgenic tobacco. and these findings consistently showed that EuCHIT73.88 could improve the resistance to black shank.

Overexpression of Nta-miR6155 confers resistance to Phytophthora nicotianae and regulates growth in tobacco (Nicotiana tabacum L.)

Tobacco black shank induced by Phytophthora nicotianae causes significant yield losses in tobacco plants. MicroRNAs (miRNAs) play a pivotal role in plant biotic stress responses and have great potential in tobacco breeding for disease resistance. However, the roles of miRNAs in tobacco plants in response to P. nicotianae infection has not been well characterized. In this study, we found that Nta-miR6155, a miRNA specific to Solanaceae crops, was significantly induced in P. nicotianae infected tobacco. Some of predicted target genes of Nta-miR6155 were also observed to be involved in disease resistance. To further investigate the function of miR6155 in tobacco during P. nicotianae infection, Nta-miR6155 overexpression plants (miR6155-OE) were generated in the Honghua Dajinyuan tobacco variety (HD, the main cultivated tobacco variety in China). We found that the Nta-miR6155 overexpression enhanced the resistance in tobacco towards P. nicotianae infections. The level of reactive oxygen species (ROS) was significantly lower and antioxidant enzyme activities were significantly higher in miR6155-OE plants than those in control HD plants during P. nicotianae infection. In addition, we found that the accumulation of salicylic acid and the expression of salicylic acid biosynthesis and signal transduction-related genes is significantly higher in miR6155-OE plants in comparison to the control HD plants. Furthermore, we found that Nta-miR6155 cleaved target genes NtCIPK18 to modulate resistance towards P. nicotianae in tobacco plants. Additionally, phenotypic analysis of miR6155-OE plants showed that Nta-miR6155 could inhibit the growth of tobacco by suppressing nitrogen uptake and photosynthesis. In conclusion, our findings indicated that miR6155 plays a crucial role in the regulation of growth and resistance against P. nicotianae infections in tobacco plants.