Seeds represent the main nutrient source for humans and domesticated animals. Previous research has shown that genetic mutants in the model plant Arabidopsis can produce larger seeds. DNA methylation, a covalent modification on DNA cytosine residues, is important for gene regulation. We investigate whether mutations in the components of the canonical RNA-directed DNA methylation pathway (RdDM pathway) can affect seed size in Arabidopsis. These genes include RNA POLYMERASE IV (POL IV), RNA POLYMERASE V (POL V), DICER-LIKE 3 (DCL3), ARGONAUTE 6 (AGO6), DOMAINS REARRANGED METHYLTRANSFERASE 2 (DRM2), and CHROMOMETHYLASE 3 (CMT3). To achieve this, DNA was extracted from the mutant and wild type plants, and PCR was performed to identify the homozygous mutant plants. The weight, length, and width of mutant and wild type seeds were measured. The results show that mutations in the different components of the RdDM pathway cause a decrease in seed size. The reciprocal crosses between wild type and POL IV and POL V mutant plants suggest that there is a potential parent-of-origin effect of the mutation on seed size. In summary, the results indicate that the canonical RdDM pathway regulates seed size in Arabidopsis.

Christine would like to thank her faculty sponsor, Dr. Wenyan Xiao, and Arthur Bartels for their support and guidance for this project.