NtWRKY70 ‐Mediated Black Stem Disease Resistance: Synergistic Antioxidant Activation and Defence Gene Upregulation

ABSTRACT WRKY, a plant‐specific transcription factor protein family, participates in various stress responses. However, reports on the association of WRKY transcription factors with tobacco diseases are lacking. Therefore, we investigated whether the tobacco transcription factor NtWRKY70 confers disease resistance by using tobacco black stem disease, caused by Phytophthora nicotianae , to study the role of NtWRKY70 in disease resistance. The expression of NtWRKY70 in tobacco overexpression lines was significantly higher than that in wild‐type (WT) plants during the infection process. The the area of infected NtWRKY70 overexpression lines stained with trypan blue was lower than that of the WT and knockout mutant lines, and the degree of damage was the lower. The net photosynthetic rate, stomatal conductance and transpiration rate of the overexpressing plants were significantly higher than those of WT and knockout mutant plants. NtWRKY70 overexpression lines showed higher superoxide dismutase, peroxidase and catalase and significantly higher phenylalanine ammonia‐lyase and polyphenol oxidase activities related to disease resistance. Additionally, , H 2 O 2 and malondialdehyde contents and relative conductivity decreased. Reverse transcription‐quantitative PCR indicated significantly upregulated expression of NtSOD , NtPOD and NtCAT in NtWRKY70 overexpression lines, enhancing the antioxidant resistance of tobacco, as well as upregulated expression of NtPAL , NtPPO and NtPR1 defence genes, further improving the disease resistance of plants. Therefore, NtWRKY70 plays an active regulatory role in resistance to P. nicotianae infection. This study provides candidate genes for future tobacco disease‐resistance breeding.