Functional divergence of two duplicated Fertilization Independent Endosperm genes in rice with respect to seed development

Abstract

Fertilization Independent Endosperm (FIE) is an essential member of Polycomb Repressive Complex 2 (PRC2) that plays important roles in the developmental regulation of plants. OsFIE1 and OsFIE2 are two FIE homologs in the rice genome. Here, we showed that OsFIE1 probably duplicated from OsFIE2 after the origin of the tribe Oryzeae, but has a specific expression pattern and methylation landscape. During evolution, OsFIE1 underwent a less intensive purifying selection than did OsFIE2. The mutant osfie1 produced smaller seeds and displayed reduced dormancy, indicating that OsFIE1 predominantly functions in late seed development. Ectopic expression of OsFIE1, but not OsFIE2, was deleterious to vegetative growth in a dose-dependent manner. The newly evolved N-terminal tail of OsFIE1 was probably not the cause of the adverse effects on vegetative growth. The CRISPR/Cas9-derived mutant osfie2 exhibited impaired cellularization of the endosperm, which suggested that OsFIE2 is indispensable for early seed development as a positive regulator of cellularization. Autonomous endosperm was observed in both OsFIE2 +À and osfie1/OsFIE2 +À but at a very low frequency. Although OsFIE1-PRC2 exhibited H3K27me3 methyltransferase ability in plants, OsFIE1-PRC2 is likely to be less important for development in rice than is OsFIE2-PRC2. Our findings revealed the functional divergence of OsFIE1 and OsFIE2 and shed light on their distinct evolution following duplication.

Genomic imprinted genes in reciprocal hybrid endosperm of Brassica napus

“…BnaA05g04610D is a homolog of AtPME17 , which can change pectin physicochemical properties, induce the reduction of galacturonic acid to modify the cell wall architecture [ 75 ]. BnaAnng26700D is a homolog of OsFIE1 , which is an essential member of polycomb repressive complex 2 (PRC2) that plays vital roles in early seed development through regulating endosperm cellularization and seed size [ 76 , 77 ].…”

The maternally expressed polycomb group gene OsEMF2a is essential for endosperm cellularization and imprinting in rice

“…Nuclear protein extraction was performed as previously reported ( Cheng et al, 2020 ), and the extracted proteins were used for western blotting. Polyclonal antibodies for H3 (Abcam, cat no.…”

“…The samples were submitted to Novogene (Tianjin) for library preparation and sequencing. For the DEG analysis, we used the CLC Genomics Workbench 12.0 software as previously described ( Cheng et al, 2020 ). The DEGs were submitted to MapMAN for pathway analysis ( Usadel et al., 2009 ).…”

“…Similar to FIE in Arabidopsis , the rice homolog OsFIE1 is imprinted ( Zhang et al., 2012 ). Although OsFIE1 plays a limited role in cellularization ( Huang et al., 2016 ), it is likely involved in the regulation of seed dormancy ( Cheng et al, 2020 ). The other FIE homolog in rice is OsFIE2 ( Luo et al., 2009 ).…”

“…(2013) have reported that OsFIE2 knockdown causes filling defects in seeds. Moreover, we have recently found that OsFIE1 and OsFIE2 functionally diverged during evolution ( Cheng et al, 2020 ). OsFIE2 is essential for early endosperm development, as evidenced by impaired cellularization in the osfie2 mutant.…”