Organisms, including mammals, invertebrates, and plants have evolved sophisticated and conserved innate immune responses to protect themselves from pathogen attacks. In these systems, host immune responses and disease resistance are achieved by modulation of a large array of genes, but how these processes are regulated is still largely unclear. Small RNAs are non-coding regulatory RNA molecules that control gene expression by mediating mRNA degradation, translational inhibition, or chromatin modification. Our work and those of others have demonstrated a role of host endogenous small RNAs, including microRNAs (miRNAs) and small interfering RNAs (siRNAs), in antibacterial innate immunity. We discovered that several pathogen-induced host endogenous siRNAs, including natural antisense transcripts-derived siRNAs (nat-siRNAs) and long siRNAs (lsiRNAs), facilitate host immune responses by posttranscriptionally silencing the negative regulators of plant immune systems. Epigenetic changes were also observed in bacteria-infected plants, however, the role of small RNA-guided DNA methylation and chromatin modification in plant immunity has not been explored. Using Arabidopsis as a model system and Illumina deep sequencing as a platform, we recently profiled the small RNA population after bacterium-challenge and identified diverse classes of endogenous small RNAs that are regulated by the infection of bacterial pathogens. We hypothesize that these pathogen-responsive small RNAs regulate the expression of genes involved in host immune responses by silencing regulators of host immunity transcriptionally or post-transcriptionally. We propose to investigate the regulation, biogenesis, and function of these pathogen-responsive small RNAs. Specifically, we will perform in depth characterization of several newly identified miRNAs, nat-siRNAs, lsiRNAs, and clustered hc-siRNAs that are particularly regulated by various strains of the bacterium Pseudomonas syringae. Predicted target genes of these small RNAs will be validated and subjected to functional analysis. These targets are likely to be components involved in plant immune response pathways. We will also characterize the hc-siRNAs that directed DNA methylation in response to bacterial infection. We will generate a whole-genome DNA-methylation map before and after bacterial infection, and correlate the siRNAs, DNA methylation, and pathogen-responsive gene expression. The proposed research will significantly advance our understanding of the mechanisms and functions of small RNAs involved in host innate immunity.

Public Health Relevance

(Relevance) Multicellular eukaryotes, including mammals, invertebrates, and plants have evolved sophisticated and conserved innate immune responses to protect themselves from pathogen attack. The proposed research will significantly advance our understanding of the mechanisms and function of small RNA-mediated gene regulation in innate immunity using the model organism Arabidopsis thaliana.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
Project #
Application #
Study Section
Cellular Signaling and Regulatory Systems Study Section (CSRS)
Program Officer
Bender, Michael T
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of California Riverside
Other Basic Sciences
Schools of Earth Sciences/Natur
United States
Zip Code
Lii, Yifan; Jin, Hailing (2014) Forward chemical screening of small RNA pathways. Methods Mol Biol 1056:95-101
Zhang, Xiaoming; Niu, DongDong; Carbonell, Alberto et al. (2014) ARGONAUTE PIWI domain and microRNA duplex structure regulate small RNA sorting in Arabidopsis. Nat Commun 5:5468
Weiberg, Arne; Wang, Ming; Bellinger, Marschal et al. (2014) Small RNAs: a new paradigm in plant-microbe interactions. Annu Rev Phytopathol 52:495-516
Zhang, Xiaoming; Lii, Yifan; Wu, Zhigang et al. (2013) Mechanisms of small RNA generation from cis-NATs in response to environmental and developmental cues. Mol Plant 6:704-15
Seo, Jang-Kyun; Wu, Jianguo; Lii, Yifan et al. (2013) Contribution of small RNA pathway components in plant immunity. Mol Plant Microbe Interact 26:617-25
Zhao, Hongwei; Sun, Ruobai; Albrecht, Ute et al. (2013) Small RNA profiling reveals phosphorus deficiency as a contributing factor in symptom expression for citrus huanglongbing disease. Mol Plant 6:301-10
Weiberg, Arne; Wang, Ming; Lin, Feng-Mao et al. (2013) Fungal small RNAs suppress plant immunity by hijacking host RNA interference pathways. Science 342:118-23
Zhang, Xiaoming; Xia, Jing; Lii, Yifan E et al. (2012) Genome-wide analysis of plant nat-siRNAs reveals insights into their distribution, biogenesis and function. Genome Biol 13:R20
Zhang, Xiaoming; Zhao, Hongwei; Gao, Shang et al. (2011) Arabidopsis Argonaute 2 regulates innate immunity via miRNA393(ýýý)-mediated silencing of a Golgi-localized SNARE gene, MEMB12. Mol Cell 42:356-66
Zhang, Weixiong; Gao, Shang; Zhou, Xiang et al. (2011) Bacteria-responsive microRNAs regulate plant innate immunity by modulating plant hormone networks. Plant Mol Biol 75:93-105

Showing the most recent 10 out of 13 publications