Role of dna methylation reprogramming in germline stress response
Cytosine methylation is an ancient epigenetic modification that carries essential regulatory functions in eukaryotic genomes. This modification is reprogramed in both male and female germlines of mammals, regulating essential germline functions. My host lab discovered that DNA methylation reprogramming also occurs in male germlines of flowering plants, such as Arabidopsis, rice and maize. This reprogramming is catalyzed by the RNA-directed DNA methylation pathway (RdDM), which methylates hundreds of genes specifically in the male germline. In Arabidopsis, this germline-specific methylation (GSM) regulates male meiosis by controlling gene transcription and splicing. It is unknown if methylation reprogramming also occurs in plant female germlines. Furthermore, our preliminary data suggest that GSM is modulated by ambient temperature. It is mysterious if and how environmental modulation of methylation reprogramming contributes to stress tolerance in plant germlines. 
I propose to answer these questions in Arabidopsis using a combination of single-cell genomics, epigenetics, genetics and developmental biology approaches. My preliminary work detected GSM in the egg companion cell and gynoecium (female organ), whose development was reported to be affected by RdDM mutations. Data also suggest that heat-induced modulation of GSM activates a heat shock gene in male meiocytes. Thus, I hypothesize that methylation reprogramming occurs and plays essential regulatory roles in the female germline, and beyond; an important function of such reprogramming is to mediate germline response to environmental stresses such as heat. Here, I will test this hypothesis and elucidate the scope, mechanism and environmental adaptation function of germline reprogramming. My discoveries will elucidate essential methylation and regulatory mechanisms in plant germlines that mediate intergenerational heredity, and establish a novel epigenetic paradigm in how germlines perceive and respond to stress.