Research Projects

Volatile organic compounds of microbial origin (mVOCs) are the ‘chemical language’ that are emitted by the microorganisms and used to interact with their plant partners. These mVOCs plausibly modulate the physiological processes in plants leading to apparent enhancement of biomass and yield. Though several encouraging reports are available on the promotional roles of mVOCs in plant growth and development, scant information is available at the fundamental level on how mVOCs influence primary metabolism leading to enhanced accumulation of photoassimilates. Moreover, studies on how mVOCs elicit the metabolic processes leading to enhanced accumulation of specialized metabolites (such as, essential oils) remain apparently unexplored. Therefore, it is necessary to understand how plants exposed to mVOCs modulate central metabolism which subsequently reprogram the specialized metabolism. It is also important to know the downstream signalling pathway in plants that functions after mVOCs perception. Therefore, this project primarily aims to reveal the modulatory roles of mVOCs in central and specialized metabolism using mint family plants as models. After isolation of promising mVOCs-emitted microorganisms from rhizosphere of chosen plants as well as from their tissues (endophytes) with capability of plant growth promoting roles, a range of experiments will be conducted using Lamiaceae plants namely Mentha spicata (spearmint), Mentha arvensis (wild mint), Mentha rotundifolia (apple mint) Melissa officinalis (lemon balm) and Ocimum citriodorum (lemon basil). Apart from producing these diverse monoterpenoids, all these chosen mint family plants also accumulate signature phenolics namely rosmarinic acid and/or methyl chavicol. As the biosynthesis of monoterpenoids and phenylpropanoids are elucidated at genetic levels in Lamiaceae, these chosen plants may serve as a springboard for exploring the capability of emitted mVOCs on modulating specialized metabolism leading to possible changes in signature metabolites. Purpose-built vessels and miniature greenhouse will be used to conduct a range of experiments where these plants will be exposed to mVOCs without physical contact with their producer microorganisms (which are cocultivated in the same vessel for release of mVOCs). After an optimal period of incubation, growth performances of these mVOCs exposed plants and will be assessed using appropriate controls (plants without exposure to specific mVOCs). Levels of phytohormones will be analysed by HPLC-based methods. Starch content will be analysed by both spectrophotometric and histochemical methods. In vitro activities of the enzymes of carbohydrate metabolism will be compared from both control and mVOCs exposed plants. Semi-targeted profiling of sugars and amino acids will be done subsequently with these plant extracts by GC-MS after appropriate derivatization(s). While Volatile terpenoids and phenylpropanoids will be analyzed by GC-MS, the non-volatile marker phenolic metabolites will be analysed using HPLC-DAD based methods. Next, RNA seq analysis will be undertaken from both control and mVOCs exposed plants to investigate the expression levels of candidate genes associated with both central and specialised metabolic pathways. From the generated RNA seq data, we shall make attempt to detect the putative genes for mVOCs receptor along with activated transcription factor genes that act in the downstream after plants perceive mVOCs signal. Apart from contributing to basic science related to the modulatory roles of mVOCs in plants, the outcome of this project is expected to generate clues for translational potential of mVOCs for promoting the accumulation of signature metabolites in mint family plants, and these will be tested in this project at small field levels to accomplish the final objective.