Plant natural products (NPs) are important sources for the discovery and development of small molecule medicines. Analysis of the genome data implies that nature's synthetic potential has been largely underestimated, and the majority of NPs have been unexplored. Over the past twenty years, many approaches have been developed to more efficiently discover novel NPs from microbial organisms. However, none of these strategies are applicable to predicting or activating biosynthetic pathways that are cryptic or of very low efficiency under normal conditions in plants. Plant NPs are believed to play an indispensable role in plants' innate immunity and defense framework. In response to the recognition of pathogens or damage by the pattern recognition receptors (PRRs), the plant activates the biosynthesis of NPs that function as defensive molecules such as antimicrobials. PRRs are surface-localized, ligand-binding, receptor-like kinases or proteins that recognize and respond to molecular signals in the environment. Genome analysis indicates that plants encode a huge number of PRRs, with the function of more than 95% being unknown even in the model plant Arabidopsis thaliana. If we can activate the downstream pathways of the unknown PRRs, plant NPs that are produced as defense or signaling molecules under various situations will be activated and discovered. Therefore, we propose to develop a strategy to engineer and redirect plant immune signaling to discover novel plant NPs. The central hypotheses are 1) plant perception complex/immune signaling pathway can be functionally reconstituted in the baker's yeast Saccharomyces cerevisiae; 2) plant PRRs can be engineered to recognize altered stimulus; and 3) the signaling and metabolic pathways downstream of target plant PRRs can be activated through introducing the engineered PRR and the corresponding stimulus. With expertise in synthetic biology and NP biosynthesis, we will verify the hypotheses and demonstrate this strategy through executing the following three specific aims, using Arabidopsis thaliana as the testbed:
Aim 1, establish a yeast platform that enables functional reconstitution of plant immune complex and high throughput phenotyping;
Aim 2, engineer plant immune receptors so they can be activated by known stimulus;
Aim 3, implement the chimeric immune receptors into the model plant for plant NP and biosynthesis discovery. The project will generate 1) discovery of novel plant NPs that may not be synthesized under normal conditions, and their native functions; 2) strategies for engineering plant pattern recognition receptors that can activate various plant immune and metabolic responses; 3) insights into how the highly complex plant signaling pathways (immune, perception, growth factor, plant hormone, etc.) are correlated and regulated. The development of this methodology is a significant step towards my long-term goals: (1) to advance the foundational understanding of phytochemical synthesis, (2) to promote the discovery of novel phytochemicals for pharmaceutical applications, and (3) to develop microbial bio-production of phytochemicals of high value as an economic approach.
Plant natural products (NPs) play an important role in drug development: More than 10% of the WHO listed essential medicines are of flowering plant origin. Analysis of the genome data implies that nature's synthetic potential has been largely underestimated and the majority of NPs have been unexplored, but few strategies have been developed to discover plant NPs that are not produced under normal conditions. In this project, we propose to develop a strategy to engineer and redirect plant immune signaling to discover novel plant NPs, the biosynthesis of which is only activated upon the recognition of pathogen or damage.