Research Projects

My lab studies the molecular mechanisms of plant immunity and pathogen virulence,  with an overall goal to develop effective and environmentally friendly strategies to control plant diseases and to ensure sufficient food production.  
Our research projects include:
  • Small RNAs and Cross-Kingdom RNAi in Plant - Pathogen Interactions
Small RNAs, including microRNAs (miRNAs) and small interfering RNAs (siRNAs), are important regulators of 
eukaryotic gene expression by guiding mRNA cleavage, translational inhibition or chromatin modification. We utilize genomics, genetics, molecular and biochemical approaches to identify and functionally characterize infection-regulated small RNAs, including those from plant hosts and from eukaryotic pathogens. My lab provided the first example of a plant endogenous siRNA that regulates plant immune responses. We further discovered that some small RNAs from aggressive fungal pathogens are delivered into host cells to hijack host RNAi machinery to suppress host immunity genes. These studies have added small RNAs to the list of pathogen effectors, which unveiled a novel virulence mechanism in aggressive eukaryotic pathogens. The transport of small RNAs from fungal pathogens to plant hosts also represents a naturally occurring cross-kingdom RNAi event. We recently show that such cross-kingdom RNAi is bi-directional, plants are also capable of delivery endogenous small RNAs into fungal pathogens to attenuate their virulence. During infection with Botrytis cinerea, plant cells package sRNAs inside exosomes, which are sent out of the plant cells and accumulate near the site of infection. These exosomes are taken up by the fungal cells efficiently, where the transferred host sRNAs inhibit the expression of fungal genes needed to cause the disease. This discovery will help us develop effective delivery methods to target plant pathogens with artificial sRNAs, with the goal of controlling plant diseases in crops.

    • Regulatory mechanisms of RNAi machinery in plant - pathogen interactions
My lab also studies the function and regulation of RNAi pathway components, mostly Argonaute (AGO) proteins in plant immunity. AGO proteins are the core components of RNAi complexes, which selectively bind with small RNAs and silence target genes with complementary sequences. We discovered that Arabidopsis AGO2 positively regulates antibacterial immunity by associating with miR393*, which targets a Golgi-localized SNARE gene MEMB12 and leads to increased secretion of antimicrobial peptide and confers resistance. Since miR393 also contributes to antibacterial immunity by suppressing auxin receptors, miR393*/miR393 represent a novel example of a miRNA*/miRNA pair that functions in the same cellular pathway (host immunity) through two distinct AGOs. We further demonstrated that small RNA duplex structures and AGO PIWI domain contribute to the selective loading of small RNAs in different AGO proteins, AGO1 and AGO2. We currently focus on the regulation and modification of AGO proteins in responses to pathogen attacks.
  • Epigenetic regulation of plant immune responses 
Surveillance of pathogen infection is mediated by intracellular NOD-like nucleotide-binding/leucine-rich-repeat receptors (NLRs) in both plants and animals. We recently discovered that some NBS-LRR genes, are under the control of specific plant chromatin remodeling proteins, as well as RNA-directed DNA methylation (RdDM) pathway. Such epigenetic regulation ensures precise expression of these resistance genes to avoid autoimmune responses or disease.