No abstract

African wild rice Oryza longistaminata, one of the eight AA-genome species in the genus Oryza, possesses highly valued traits, such as the rhizomatousness for perennial rice breeding, strong tolerance to biotic and abiotic stresses, and high biomass production on poor soils. To obtain the high-quality reference genome for O. longistaminata we employed a hybrid assembly approach through incorporating Illumina and PacBio sequencing datasets. The final genome assembly comprised only 107 scaffolds and was approximately ∼363.5 Mb, representing ∼92.7% of the estimated African wild rice genome (∼392 Mb). The N50 lengths of the assembled contigs and scaffolds were ∼46.49 Kb and ∼6.83 Mb, indicating ∼3.72-fold and ∼18.8-fold improvement in length compared to the earlier released assembly (∼12.5 Kb and 364 Kb, respectively). Aided with Hi-C data and syntenic relationship with O. sativa, these assembled scaffolds were anchored into 12 pseudo-chromosomes. Genome annotation and comparative genomic analysis reveal that lineage-specific expansion of gene families that respond to biotic-and abiotic stresses are of great potential for mining novel alleles to overcome major diseases and abiotic adaptation in rice breeding programs.

No abstract

Photoperiod sensitivity is a dominant determinant for the phase transition in cereal crops. CCT (CONSTANS, CO-like, and TOC1) transcription factors (TFs) are involved in many physiological functions including the regulation of the photoperiodic flowering. However, the functional roles of CCT TFs have not been elucidated in the wild progenitors of crops. In this study, we identified 41 CCT TFs, including 19 CMF, 17 COL, and five PRR TFs in Oryza rufipogon, the presumed wild ancestor of Asian cultivated rice. There are thirty-eight orthologous CCT genes in Oryza sativa, of which ten pairs of duplicated CCT TFs are shared with O. rufipogon. We investigated daily expression patterns, showing that 36 OrCCT genes exhibited circadian rhythmic expression. A total of thirteen OrCCT genes were identified as putative flowering suppressors in O. rufipogon based on rhythmic and developmental expression patterns and transgenic phenotypes. We propose that OrCCT08, OrCCT24, and OrCCT26 are the strong functional alleles of rice DTH2, Ghd7, and OsPRR37, respectively. The SD treatment at 80 DAG stimulated flowering of the LD-grown O. rufipogon plants. Our results further showed that the nine OrCCT genes were significantly downregulated under the treatment. Our findings would provide valuable information for the construction of photoperiodic flowering regulatory network and functional characterization of the CCT TFs in both O. rufipogon and O. sativa.

HighlightAlternative splicing of the basic chitinase gene PR3b requires genes in the NIC loci of low-nicotine mutants of Burley 21 tobacco.