Intersubspecific hybrid sterility is a common form of reproductive isolation in rice (Oryza sativa L.), which significantly hampers the utilization of heterosis between indica and japonica varieties. Here, we elucidated the mechanism of S7, which specially causes Aus-japonica/indica hybrid female sterility, through cytological and genetic analysis, map-based cloning, and transformation experiments. Abnormal positioning of polar nuclei and smaller embryo sac were observed in F 1 compared with male and female parents. Female gametes carrying S7 cp and S7 i were aborted in S7 ai /S7 cp and S7 ai /S7 i , respectively, whereas they were normal in both N22 and Dular possessing a neutral allele, S7 n . S7 was fine mapped to a 139-kb region in the centromere region on chromosome 7, where the recombination was remarkably suppressed due to aggregation of retrotransposons. Among 16 putative open reading frames (ORFs) localized in the mapping region, ORF3 encoding a tetratricopeptide repeat domain containing protein was highly expressed in the pistil. Transformation experiments demonstrated that ORF3 is the candidate gene: downregulated expression of ORF3 restored spikelet fertility and eliminated absolutely preferential transmission of S7 ai in heterozygote S7 ai /S7 cp ; sterility occurred in the transformants Cpslo17-S7 ai . Our results may provide implications for overcoming hybrid embryo sac sterility in intersubspecific hybrid rice and utilization of hybrid heterosis for cultivated rice improvement.KEYWORDS hybrid sterility; female gamete; tetratricopeptide repeat (TPR); transgenic; rice (Oryza sativa L.) H YBRIDIZATION between two different species can lead to a distinct phenotype, which can also be fitter than the parental lineage. However, reproductive isolation maintains the integrity of a species over time, reducing or directly impeding gene flow between individuals of different species (Mayr 1942;Grant 1981;Coyne and Orr 2004;Widmer et al. 2009;Baack et al. 2015). The mechanisms of reproductive isolation were classified into two broad categories: prezygotic and postzygotic isolation mechanisms (Mayr 1963;Levin 1978;Sweigart and Willis 2012;Chen et al. 2014). According to the classical Dobzhansky-Muller model, postzygotic isolation results from a deleterious interaction between functionally diverged genes from the hybridizing species (Dobzhansky 1937;Ting et al. 1998;Barbash et al. 2003;Presgraves et al. 2003;Brideau et al. 2006;Bayes and Malik 2009;Ferree and Barbash 2009;Phadnis and Orr 2009;Tang and Presgraves 2009;White et al. 2011). Genes for hybrid sterility, a common pattern of postzygotic isolation, have been reported in several organisms, including fungi, animals, and plants (Brideau et al. 2006;Lee et al. 2008;Bikard et al. 2009;De Vienne et al. 2009).Major progress has been made in rice and the interspecific and intersubspecific hybrid sterilities are perhaps the best known examples (Chen et al. 2008;Long et al. 2008 Wan and Ikehashi 1995;Zhu et al. 2005;Li et al. 2007;Zhao et al. 2007;Chen et...

The largest group of deubiquitinases—ubiquitin-specific proteases (UBPs)—perform extensive and significant roles in plants, including the regulation of development and stress responses. A comprehensive analysis of UBP genes has been performed in Arabidopsis thaliana, but no systematic study has been conducted in moso bamboo (Phyllostachys edulis). In this study, the genome-wide identification, classification, gene, protein, promoter region characterization, divergence time, and expression pattern analyses of the UBPs in moso bamboo were conducted. In total, 48 putative UBP genes were identified in moso bamboo, which were divided into 14 distinct subfamilies in accordance with a comparative phylogenetic analysis using 132 full-length protein sequences, including 48, 27, 25, and 32 sequences from moso bamboo, A. thaliana, rice (Oryza sativa), and purple false brome (Brachypodium distachyon), respectively. Analyses of the evolutionary patterns and divergence levels revealed that the PeUBP genes experienced a duplication event approximately 15 million years ago and that the divergence between PeUBP and OsUBP occurred approximately 27 million years ago. Additionally, several PeUBP members were significantly upregulated under abscisic acid, methyl jasmonate, and salicylic acid treatments, indicating their potential roles in abiotic stress responses in plants.