OsSPL regulates meiotic fate acquisition in rice

Abstract

In angiosperms, the key step in sexual reproduction is successful acquisition of meiotic fate. However, the molecular mechanism determining meiotic fate remains largely unknown. Here, we report that OsSPOROCYTELESS (OsSPL) is critical for meiotic entry in rice (Oryza sativa). We performed a large-scale genetic screen of rice sterile mutants aimed to identify genes regulating meiotic entry and identified OsSPL using map-based cloning. We showed that meiosis-specific callose deposition, chromatin organization, and centromere-specific histone H3 loading were altered in the cells corresponding to pollen mother cells in Osspl anthers. Global transcriptome analysis showed that the enriched differentially expressed genes in Osspl were mainly related to redox status, meiotic process, and parietal cell development. OsSPL might form homodimers and interact with TEOSINTE BRANCHED1/CYCLOIDEA/PCF (TCP) transcription factor OsTCP5 via the SPL dimerization and TCP interaction domain. OsSPL also interacts with TPL (TOPLESS) corepressors, OsTPL2 and OsTPL3, via the EAR motif. Our results suggest that the OsSPL-mediated signaling pathway plays a crucial role in rice meiotic entry, which appears to be a conserved regulatory mechanism for meiotic fate acquisition in angiosperms.

Ornithine δ‐aminotransferase is critical for floret development and seed setting through mediating nitrogen reutilization in rice

“…RNA in situ hybridization was completed as previously described (Cheng et al, 2014;Ren et al, 2018). In brief, gene-specific segments were amplified by PCR and cloned into the pEASY-Blunt simple vector.…”

The OsRR24/LEPTO1 Type-B Response Regulator is Essential for the Organization of Leptotene Chromosomes in Rice Meiosis

“…Preleptotene meiocytes can be observed easily in early developed rice anthers. PMCs possess a specialized pattern for CENH3 loading and show distinguishable immunofluorescence signals of CENH3 at preleptotene (Ravi et al, 2011;Ren et al, 2018). In the lepto1 mutant, PMCs were normal in appearance, with a large nucleus and nucleolus, and preleptotene chromosomes were observed in lepto1 PMCs with bright CENH3 signals.…”

“…Meiosis involves a specific CENH3 loading pattern that is different from that in mitosis, and the CENH3 foci in preleptotene meiocytes become brighter than those in somatic cells (Ren et al, 2018). Therefore, we detected the immunofluorescence signal intensity of CENH3 foci in transverse sections of anthers to investigate whether meiosis initiates in the germ cells of the lepto1 mutant.…”

“…The lepto1-cas9 mutant was produced by CRISPR-Cas9 gene editing in the japonica rice variety Yandao 8. The Osspl and Osam1 mutants used in this study were described previously (Che et al, 2011;Ren et al, 2018). Guangluai 4 was used as the wild type.…”

“…In Arabidopsis (Arabidopsis thaliana), a model eudicot species, reloading of the centromere histone H3 variant (CENH3) takes place during the G2 stage, and the premeiotic stage involves specialized loading of CENH3 (Lermontova et al, 2006;Ravi et al, 2011). Also, observations in the monocot rice (Oryza sativa) demonstrate that prophase I meiocytes have larger CENH3 foci than those in the somatic cells, suggesting that a greater amount of CENH3 loading is related to the specialized meiotic process (Ren et al, 2018).…”