Munronin O, a potential activator for plant resistance

Area of Science:

• Phytochemistry
• Plant Pathology
• Biochemistry

Background:

• Limonoids are a class of terpenoids with diverse biological activities.
• Plant viruses, such as tobacco mosaic virus (TMV), cause significant agricultural losses.
• Developing natural compounds to enhance plant defense mechanisms is crucial for sustainable agriculture.

Purpose of the Study:

• To isolate and characterize limonoids from Munronia henryi.
• To evaluate the antiviral activities of these compounds against TMV.
• To investigate the mechanism of action, including the induction of systemic acquired resistance (SAR).

Main Methods:

• Isolation and structural elucidation of limonoids using chromatographic and spectroscopic techniques.
• In vitro antiviral assays to determine inactivating, protective, and curative activities against TMV.
• Evaluation of SAR induction potential, defense-related enzyme activity, salicylic acid (SA) content, and gene expression analysis.

Main Results:

• Eight limonoids (1-8) were isolated, with Munronin O (1) showing the most potent protective activity against TMV (EC50 = 91.5 μg/mL).
• Compounds 7 and 8 also demonstrated significant antiviral activities.
• Munronin O effectively induced SAR, enhanced defense-related enzyme activity, increased SA content, inhibited TMV CP expression, and upregulated defense genes.

Conclusions:

• Munronin O is a promising natural compound for inducing plant resistance against TMV.
• The findings suggest Munronin O acts by activating plant defense pathways.
• This research highlights the potential of Munronia henryi limonoids as novel plant activators for disease management.