| Project Detail |
In flowering plants, DNA methylation reprogramming occurs in meiocytes through RNA-directed DNA methylation pathway (RdDM) mediated by 24-nucleotide small interfering RNAs (siRNAs). My host lab discovered that these siRNAs are transcribed from transposable element (TE) in tapetal cells (tapetum) and transported to male meiocyte. In meiocytes, these siRNAs induce methylation at genes (MetGenes) with similar (but not identical) sequences, and thereby regulate MetGene expression and promote meiosis. The ability of siRNAs to target loci with reduced sequence homology is unique to meiocytes: in tapetum and somatic tissues, RdDM only targets TE with perfect sequence homology to siRNAs. The broad-targeting competence of tapetum siRNAs allows the targeting of MetGenes and fast-evolving TE in meiocytes, however, it is unclear how the broad targeting is achieved and comfined to the meiocytes. My preliminary work discovered several meiocyte-specific RdDM homologues, which I hypothesize to permit siRNA mismatch targeting. Furthermore, I found that RdDM mutants are hypersensitive to heat stress in meiocyte development, suggesting RdDM mediates heat stress response in meiocytes. Harnessing single-cell multi-omics, biochemistry and bio-imaging approaches, I aim to: 1) identity germline-specific RdDM homologues responsible for MetGenes targeting; 2) decipher how methylation of MetGenes are mediated by lncRNAs; and 3) uncover how the methylation reprogramming of MetGenes contributes to mediating male germline thermotolerance. My discoveries will elucidate essential siRNA regulatory mechanisms that mediate intergenerational heredity in plants and establish a novel epigenetic paradigm in how meiocytes perceive and respond to heat stress, essential knowledge for building crop resilience under climate change. This in-depth knowledge of cell- and site-specific RdDM pathway will also inform the generation of novel crop improvement tools by the engineering of methylation at gene families. |
