Heterologous WRKY and NAC transcription factors triggered resistance in Nicotiana benthamiana

Abstract

Background: SA (Salicylic acid) and JA (Jasmonic acid)/ET (Ethylene) are the defense and growth hormone regulators involved in alleviating the biotic and abiotic stresses. WRKY and NAC genes are contributors to plant resistance due to their active role in SA and JA/ET defense mechanism. Methods: WRKY and NAC transcription factors (ptHR293 and ptHR759, respectively) were serially selected (by performing cDNA library functional screening, homology analysis, antioxidant enzymes, ROS burst, callose deposition and qRT-PCR analysis) from Pinellia ternata and transformed into Nicotiana benthamiana. Hybrids were generated to analyze the stability of disease resistance. UPLC-QTOF-MS was performed to study the bioactive compounds. Results: Study demonstrated that ptHR293 and ptHR759 had potential to trigger ROS burst and callose deposition in N. benthamiana together with the activation of PR-genes and antioxidant enzymes. In transformed N. benthamiana, relative expression of PR-1a (Pathogenesis related-1a) and PDF1.2 (Plant defensin 1.2) was upregulated upto 21 folds and 4 folds for ptHR293 transformed N. benthamiana. While PR-1a and PDF1.2 exhibited 8 folds and 26 folds upregulation for ptHR759 transformed N. benthamiana. ptHR293 + ptHR759-F1 hybrids also exhibited a significant level of PR-gene expression. Significantly high resistance against Botrytis cinerea without influencing the standard seed germination, root and shoot length of transformed N. benthamiana was also observed. A significant induction of bioactive compounds was also observed in ptHR293 transformed N. benthamiana. Conclusion: Conclusively, heterologous transcription factors, ptHR293 and ptHR759, perform their specific role in the activation of SA and JA/ET mediated defense mechanism.

Keywords

• Hypersensitive response
• Nicotiana benthamiana
• Transcription factor
• WRKY
• 3,4-Dichloromaleimide