Welcome to the Brodersen Lab

Small RNAs in plants: fundamental regulators of gene expression

Small silencing RNAs are the hallmark of a collection of gene regulatory mechanisms known as RNA silencing. In RNA silencing, the small (20-30 nucleotide long) RNAs act as specificity determinants that use base pairing to guide repressive protein complexes to complementary RNA molecules. This simple, versatile mehanism is of tremendous importance in regulation of mRNAs important for plant and animal development and stress responses, particularly via a specific class of small RNAs called microRNAs (miRNAs).

In plants and animals, small RNA based mechanisms are also at the heart of epigenetic silencing mechanisms that act to limit transposon activity and thereby contribute to the maintenance of genome stability. In a related process, RNA silencing is also being employed as an RNA based immune system to combat infections by RNA viruses in plants and insects. It is an important objective of our research to understand how the RNA silencing mechanism is coupled to protein-based sensing of pathogens via immune receptors. This project is starting January 2014, and is supported by a Sapere Aude grant from the Danish Council for Independent Research. More details about this project can be found at my Sapere Aude home page.

Our group also maintains a strong focus on understanding the mechanistic basis of miRNA function in plants. We make extensive use of genetic screens coupled to next-generation DNA sequencing to identify new components involved in discrete steps of the pathway. We also employ biochemical methods to study protein complexes with important functions in the pathway. We have previously shown that a miRNA effector complex is associated with a membrane compartment, and are studying how the membrane association occurs and what its functional role is. We are also interested in elucidating how miRNAs bring about translational repression of mRNA in plants, and understanding the relation of this mode of regulation to mRNA degradation.

Selection of a mutant defective in miRNA function using Arabidopsis genetics. A constitutively expressed Green Fluorescent Protein (GFP) mRNA with a site complementary to the endogenous miR171 gives little GFP fluorescence because of silencing guided by miR171 (top panel). This can be used to select mutants with defective miRNA function, such as mbd2 (bottom panel).