Epigenetic regulation of sexual lineage development in plants

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In flowering plants, reproduction is carried out by two specialized cellular sexual lineages (SLs). SLs initiate as meiocytes, each producing four spores via meiosis; these spores then divide and differentiate into gametes and their companion cells. Although past studies have identified a network of genes required for SL function, the genes required for the initiation of SLs are few, and it is unknown how these few genes execute the massive shift of transcription repertoire in the transition between somatic and reproductive development.

My preliminary studies suggest that a SL-specific RNA-directed DNA methylation pathway (RdDM) promotes male SL development by regulating the expression of key reproductive and somatic genes, with mutations in this pathway causing meiotic defects. In this proposal I will investigate the mechanism by which male SL development is regulated by the SL-specific RdDM in the model plant Arabidopsis thaliana. First, I will use reverse genetics and Illumina sequencing to precisely determine the effect of RdDM on the SL-specific expression of genes in the 4 types of male SL cells, and will explore how RdDM regulates SL development through these genes by characterizing the functions of two novel candidate genes. Second, I will decipher the mechanism underlying SL-specific RdDM activity using a combination of genomic, forward genetic and developmental biology approaches to identify novel SL-specific proteins and non-coding RNAs that target RdDM.

My proposed research will lead to the discovery of novel genetic and epigenetic regulators of SL development and function, which can be exploited to improve crop yield. My work will also greatly expand our knowledge of epigenetic regulation of plant development, as it demonstrates, for the first time, how a DNA methylation mechanism is adapted by a specific lineage of cells to promote their biological function – a mode of regulation that will likely be relevant to developmental processes outside the SL.

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