OsLFR is essential for early endosperm and embryo development by interacting with SWI/SNF complex members in Oryza sativa

Abstract

Rice (Oryza sativa L.) endosperm provides the developing embryo with nutrients and provides human beings with a staple food. The embryo eventually develops into a new sporophyte generation. Despite their important roles, the molecular mechanisms underlying early-stage endosperm and embryo development remain elusive. Here, we established the fundamental functions of rice OsLFR, an ortholog of the Arabidopsis SWI/SNF chromatin-remodeling complex (CRC) component LFR. OsLFR was expressed primarily in the rice spikelets and seeds, and the OsLFR protein was localized to the nucleus. We conducted genetic, cellular and molecular analyses of loss-of-function mutants and transgenic rescue lines. OsLFR depletion resulted in homozygous lethality in the early seed stage through endosperm and embryo defects, which could be successfully recovered by the OsLFR genomic sequence. Cytological observations revealed that the oslfr endosperm had relatively fewer free nuclei, had abnormal and arrested cellularization, and demonstrated premature programed cell death: the embryo was reduced in size and failed to differentiate. Transcriptome profiling showed that many genes, involved in DNA replication, cell cycle, cell wall assembly and cell death, were differentially expressed in a knockout mutant of OsLFR (oslfr-1), which was consistent with the observed seed defects. Protein-protein interaction analysis showed that OsLFR physically interacts with several putative rice SWI/SNF CRC components. Our findings demonstrate that OsLFR, possibly as one component of the SWI/SNF CRC, is an essential regulator of rice seed development, and provide further insights into the regulatory mechanism of early-stage rice endosperm and embryo development.

CTP synthase is essential for early endosperm development by regulating nuclei spacing

“…Early endosperm development consists of the syncytial stage from 1 to 2 DAP and the cellularization stage at 3 DAP in rice (Lopes and Lar‐kins, 1993; Hara et al ., 2015; Qi et al ., 2020). To examine potential defects in detail, WT and mutant seeds were harvested in the early stages of development (Figure 4).…”

“…In addition, several studies have indicated that spikelet hull size depends on both cell proliferation and expansion (Lyu et al ., 2020; Yang et al ., 2020). Although endosperm development plays a major role in controlling the quality and quantity of rice grains, the mechanisms underlying the early stages of cereal endosperm development remain largely unknown (Qi et al ., 2020).…”

“…Although several genes associated with cereal endosperm storage have been investigated, only a few genes affecting early endosperm development have been identified in rice (Kurata et al ., 2005; Zhou et al ., 2013). Rice plants with mutations in the gene LEAF AND FLOWER‐related ( OsLFR ), which encodes an interaction partner of SWITCH/SUCROSE NON‐FERMENTABLE (SWI/SNF) in the ATP‐dependent chromatin‐remodelling complex, display abnormal endosperm development (Qi et al ., 2020). While the number of syncytial nuclei in oslfr‐1 and wild‐type (WT) endosperm is similar at 24 hours after pollination (HAP), at 32 HAP and beyond, the number of free nuclei at the periphery of oslfr‐1 endosperm is much lower than in WT endosperm, suggesting that this gene functions in syncytial nuclei formation.…”

Genome-Wide Association Study to Map Genomic Regions Related to the Initiation Time of Four Growth Stage Traits in Soybean

“…In the two remaining QTN regions associated with DMI, the LFR ( At3g22990 ) gene coded an ARM repeat superfamily protein and was identified in the qGm02-1 region. Its ortholog in rice, OsLFR , resulted in homozygous lethality in the early seed stage through endosperm and embryo defects via its depletion ( Qi et al, 2020 ). Another gene, ARR6 (At3g47620) was reported as a response regulator of cytokinins, which could regulate the response to cytokinin stimulus and thus delay leaf senescence.…”

Rice LEAFY COTYLEDONE1 regulates embryonic envelope development and chlorophyll biogenesis in embryo

“…Hundreds of mutants showing abnormal embryo development have been isolated in rice (Hong et al, 1995;Nagato et al, 1989). In the past two decades, several key genes governing rice embryogenesis, embryo patterning, and organogenesis have been cloned, substantially expanding our understanding of the embryo development regulation in rice at a molecular level (Ishimoto et al, 2019;Yi et al, 2016;Sazuka et al, 2009;Nosaka et al, 2007;Hibara et al, 2009;Qi et al, 2020;Huang et al, 2017). However, ironically, several fundamental questions, such as identities and their homologies of the scutellum, coleoptile, coleorhiza, and epiblast, remained unanswered, although the debate has been provoked for centuries (Brown, 1960(Brown, , 1965Xu et al, 1999).…”