Epsilon Archive for Student Projects

Abstract

Flowering plants exhibit the unique feature of double fertilization, resulting in the formation of embryo and endosperm. The endosperm provides nourishment and supports embryo growth and germination. Proper endosperm development is crucial, as its failure leads to embryo arrest and seed lethality. Hybridization of plants with varying ploidy levels leads to the establishment of an interploidy hybridization barrier in the endosperm termed as the ‘triploid block’. Deregulation of imprinted genes in the triploid block is linked to its establishment. PEG2 is an imprinted paternally expressed gene (PEG) that has been shown to establish a postzygotic interploidy hybridization barrier in triploid seeds of Arabidopsis thaliana. The transcript of PEG2 acts as a sponge for the small interfering siRNA854 in the endosperm, likely preventing its interaction with other target genes, causing the triploid block. The 21-bp long target sequence in PEG2 is essential for the formation of the triploid block. In the Col-0 accession, siRNA854 causes translational repression of PEG2 owing to incomplete sequence complementarity between the target sequence and siRNA854. Interestingly, different accessions of Arabidopsis exhibit natural sequence variation in the siRNA854 target site in PEG2. In this project, it was found that the intraspecific sequence variation is non-causal for the accession-specific triploid block phenotype, whereas the accession-specific expression levels of PEG2 correlate with frequencies of collapsed seeds obtained in the paternal excess crosses. Additionally, knock-out mutants of PEG2 were generated using CRISPR/Cas9 gene editing to enable further understanding of its molecular function.