OsPIE1, the Rice Ortholog of Arabidopsis PHOTOPERIOD-INDEPENDENT EARLY FLOWERING1, Is Essential for Embryo Development

Abstract

BackgroundThe SWR1 complex is important for the deposition of histone variant H2A.Z into chromatin necessary to robustly regulate gene expression during growth and development. In Arabidopsis thaliana, the catalytic subunit of the SWR1-like complex, encoded by PIE1 (PHOTOPERIOD-INDEPENDENT EARLY FLOWERING1), has been shown to function in multiple developmental processes including flowering time pathways and petal number regulation. However, the function of the PIE1 orthologs in monocots remains unknown.Methodology/FindingsWe report the identification of the rice (Oryza sativa) ortholog, OsPIE1. Although OsPIE1 does not exhibit a conserved exon/intron structure as Arabidopsis PIE1, its encoded protein is highly similar to PIE1, sharing 53.9% amino acid sequence identity. OsPIE1 also has a very similar expression pattern as PIE1. Furthermore, transgenic expression of OsPIE1 completely rescued both early flowering and extra petal number phenotypes of the Arabidopsis pie1-2 mutant. However, homozygous T-DNA insertional mutants of OsPIE1 in rice were embryonically lethal, in contrast to the viable mutants in the orthologous genes for yeast, Drosophila and Arabidopsis (Swr1, DOMINO and PIE1, respectively).Conclusions/SignificanceTaken together, our results suggest that OsPIE1 is the rice ortholog of Arabidopsis PIE1 and plays an essential role in rice embryo development.

A phosphoproteomic landscape of rice (Oryza sativa) tissues

“…As the closet ortholog of AtPIE1 in rice, OsPIE1 exhibits conserved gene structure, similar expression pattern, and could rescue the delayed flowering and flower defects in the Arabidopsis pie1 mutants. However, ospie1 homozygous mutants were embryonically lethal, which was not observed in Arabidopsis, suggesting its unique roles in embryogenesis (Xu et al ). Histone acetylation in plants was implicated in the control of the panicle development and flowering time.…”

H2A.Z mediates different aspects of chromatin function and modulates flowering responses in Arabidopsis

“…Interestingly, as for yeast and animal histone variants, the H2A.Z‐encoding HTA9 gene is expressed independently of the cell cycle, whereas the expression of HTA11 and HTA8 is linked to the S phase, similarly to canonical H2A (March‐Diaz and Reyes, ), suggesting that Arabidopsis H2A.Z variants could play non‐redundant roles and could also perform different functions to those in other eukaryotes. The SWR1–C is also likely to be conserved in monocotyledonous species as a putative ortholog of PIE1 , and three genes encoding H2A.Z proteins ( HTA705 , HTA712 and HTA713 ) have been identified in Oryza sativa (rice; Hu and Lai, ; Xu et al ., ).…”

Identification and molecular characterization of a low acid phosphatase 3 (lap3) mutant based on the screening of an Arabidopsis activation-tagged population

“…Considering the closely linked co-segregation of the lap3 phenotype for root APase activity with its genotypic segregation, the lossof-function phenotype in lap3 probably occurred due to the dominant mutation effect of the T-DNA inserted in the lap3 genome. Phenotypic and genotypic segregation with a ratio of 2:1, which was observed in the self-pollinated lap3 progeny, is well known to occur for homozygous lethal mutations (Kandasamy et al 2005;Xu et al 2010). The lethality could be due to a failure or defects at any stage of reproductive development, such as reduced fertility of gametes, failure of fertilization, or abortion of embryo development (Xu et al 2010).…”

“…Phenotypic and genotypic segregation with a ratio of 2:1, which was observed in the self-pollinated lap3 progeny, is well known to occur for homozygous lethal mutations (Kandasamy et al 2005;Xu et al 2010). The lethality could be due to a failure or defects at any stage of reproductive development, such as reduced fertility of gametes, failure of fertilization, or abortion of embryo development (Xu et al 2010). The mechanism underlying the homozygous lethality of the lap3 progeny needs to be elucidated in the future.…”