Plant-microbial interaction: The mechanism and the application of microbial elicitor induced secondary metabolites biosynthesis in medicinal plants

Plants and microbes interact with each other via different chemical signaling pathways. At the risophere level, the microbes can secrete molecules, called elicitors, which act on their receptors located in plant cells. The so-called elicitor molecules as well as their actions differ according to the mcirobes and induce different bilogical responses in plants such as the synthesis of secondary metabolites. Microbial compounds induced phenotype changes in plants are known as elicitors and signaling pathways which integrate elicitor's signals in plants are called elicitation. In this review, the impact of microbial elicitors on the synthesis and the secretion of secondary metabolites in plants was highlighted. Moreover, biological properties of these bioactive compounds were also highlighted and discussed. Indeed, several bacteria, fungi, and viruses release elicitors which bind to plant cell receptors and mediate signaling pathways involved in secondary metabolites synthesis. Different phytochemical classes such as terpenoids, phenolic acids and flavonoids were synthesized and/or increased in medicinal plants via the action of microbial elicitors. Moreover, these compounds compounds exhibit numerous biological activities and can therefore be explored in drugs discovery.