Rice interploidy crosses disrupt epigenetic regulation, gene expression, and seed development
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ABSTRACT: Seed development in angiosperms requires a 2:1 maternal-to-paternal genome ratio (2m:1p) in the endosperm. When the ratio is disrupted, the seed development is impaired. Rice interploidy crosses result in endosperm failures. Here we report that the defective endosperm was associated with nonadditive expression of small RNAs and protein-coding genes. Interestingly, 24-nt siRNAs were enriched in the 5’ and 3’ flanking sequences of nonadditively expressed genes in the interploidy crosses and negatively associated with the expression of imprinted genes. Furthermore, some PRC2 gene family members and the genes for DNA methylation including OsMET1b and OsCMT3a were upregulated in the 2X4 cross but repressed in the reciprocal cross. These different epigenetic effects could lead to precocious or delayed cellularization during endosperm development. Notably, many endosperm-preferred genes including starch metabolic and storage protein genes during grain filling were associated with DNA methylation or H3K27me3 and repressed in both 2X4 and 4X2 crosses. WUSCHEL homeobox2 (WOX2)-like (WOX2L), an endosperm-preferred gene, was expressed specifically in the rice endosperm, on contrary to WOX2 expression in the Arabidopsis embryo. CRISPR/Cas9 editing of WOX2L in transgenic rice blocked starch and protein accumulation, resulting in seed abortion. In addition to gene repression, disrupting epigenetic process in the interploidy crosses also induced expression of stress-responsive genes. Thus, maintaining the 2m:1p genome ratio in the endosperm is essential for normal grain development in rice and other cereal crops.
ORGANISM(S): Oryza sativa Japonica Group
PROVIDER: GSE65149 | GEO | 2018/08/31
REPOSITORIES: GEO
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