Beta-Aminobutyric acid-mediated enhancement of resistance in tobacco against TMV and consideration of its capability in wounded tobacco plants.

Systemic acquired resistance (SAR) is an important component of disease-resistance arsenal of plants, and is associated with enhanced potency of activating local and systemic defense-related responses upon pathogen attack. In this report, we demonstrated that pre-treatment with beta-aminobutyric acid (BABA), a new elicitor of SAR in the plants, enhanced resistance against tobacco mosaic virus (TMV) in a temperately-sensitive tobacco (Nicotiana tabacum L.) cultivar Yunyan 85. The resistance is based on the elicitation of defense-related responses induced by BABA that brings the TMV-susceptible tobacco plants to a defense-ready state, even before exposure to the pathogen. The induced resistance was strongly associated with potentiated activation of defense-related enzymes [phenylalanine ammonia lyase (PAL) and polyphenol oxidase (PPO)] activities, proportional to the concentration of the BABA sprayed. Interestingly, simultaneous clipping, an important agricultural practice in tobacco production, attenuated BABA-mediated enhancement of TMV resistance in tobacco. The changes in the defense-related enzymes activities indicated that the interaction between BABA and wounding was reciprocally antagonistic. Moreover, such a negative interaction regulated the expression of defense-related enzymes. depending on the time of induction.