In the past two decades, significant progress has been made in understanding how plants control the production of messenger RNAs encoding defense proteins when challenged by pathogens, but very little is known about whether and how translation of these messenger RNAs is regulated to produce proteins. With the development of a sequencing-based technology for measuring the rate of messenger RNA translation, it becomes clear that defense protein synthesis is tightly regulated in plants. This project aims to understand how this regulation is carried out and to identify messenger RNA features and important molecules involved in this regulation. The success of this project will not only fill a gap in the knowledge of the plant immune mechanisms, but also revolutionize strategies of engineering disease resistant crops by more precisely control defense proteins production. This new strategy will enable engineering broad-spectrum disease resistance without compromising plant fitness, leading to reduced use of pesticides and lightening of selective pressure for resistant pathogens. This project will also result in training of scientists from high school students to postdoctoral researchers in performing frontier research.
The long-term goal of this project is to elucidate the translational regulatory mechanisms of plant immune responses. Studies of TBF1, a key plant immune transcription factor (TF), showed that its translation is controlled by two upstream open reading frames (uORFs). These uORFs normally block ribosomes from reaching the major ORF. Upon immune induction, this inhibitory effect is rapidly alleviated, leading to TBF1 translation. This suggests that de-repressing translation of pre-existing immune TF mRNA may be a strategy for rapid response to pathogen challenge. Global translatome profiling using ribosome footprinting showed that during pattern-triggered immunity (PTI), changes in translation did not correlate well with transcription. Genes with altered translational efficiency (TE) during PTI belong to diverse functional groups and contain novel regulators of this immune response. Moreover, an mRNA consensus (uR-motif) was found to be significantly enriched in the 5' leader regions of transcripts with increased TE during PTI. This project aims to generate more translatome profiles and the first plant tRNAome datasets, essential for studying global translational changes during plant defense responses, and elucidate how tRNA level changes, mRNA sequence features (e.g., uORFs and R-motif), and trans-acting factors regulate translation. The project will lead to insight into how plants selectively translate defense-related proteins and identify new regulators of different immune responses. The project will also involve training of two postdoctoral researchers and enable continuation in outreach activities, including hosting lab tours for local high school and community college students, and mentoring for the SROP Program for minority undergraduate summer research.
