Mechanisms of Small RNA-Mediated Silencing in Chlamydomonas

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RNA interference (RNAi) is a cellular process that regulates gene expression and acts as a defense system in plants and animals. This pathway relies on small RNAs (sRNAs) to identify targets, which are then suppressed by a variety of molecular mechanisms. Microalgae are an important and sustainable feedstock for producing diverse biomaterials and nutraceuticals, but improving their productivity is constrained by limited knowledge of how they control gene expression and metabolism. This project will contribute to our understanding of the role of sRNAs in microalgae and to the development of RNAi tools for practical applications (such as RNAi-based crop protection strategies for algal mass culturing). The research will also contribute to the training of undergraduate and graduate students and one postdoctoral fellow. Recruitment of students from underrepresented groups in the sciences, potential first-generation college students, or those that have financial needs will be enabled by participation in several educational programs at the University of Nebraska-Lincoln.Several aspects of sRNA function in eukaryotes, particularly how sRNAs mediate translational repression, remain poorly understood. One key problem is an incomplete knowledge of the components of sRNA-effector complexes and their potential modulation in response to internal developmental programs and/or external cues. This project will provide insight into aspects of sRNA function, particularly the translation repression of polyribosome-associated transcripts. In the alga Chlamydomonas reinhardtii, a homolog of the Drosophila VASA INTRONIC GENE (VIG) is involved in this process. The research will: (i) characterize the interplay between VIG and Argonaute effector complexes in sRNA-mediated translation repression by several proteomic approaches; (ii) isolate additional genes involved in sRNA-mediated translation repression by using an insertional mutagenesis screen; and (iii) characterize the biogenesis and potential function of a novel class of Chlamydomonas sRNAs, similar in length to the metazoan PIWI-interacting RNAs. Since sRNA-mediated repression of polyribosomal mRNAs also occurs in land plants and animals, the results may contribute to our understanding of the evolution (i.e., conservation vs. divergence) of sRNA-mediated epigenetic mechanisms in eukaryotes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.