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Anther-specific expression of OsRIP1 causes dominant male sterility in rice To clone I Dms1 i , we constructed a near-isogenic line (NIL) I -NJ4 i SP I Dms1 i sp contains the genetic background of the I japonica i rice variety I Ningjing4 i ( I NJ4 i ) but carries a chromosome segment insertion with I Dms1 i introduced from the mutant donor (Figure S1). When using the anther-specific I EAT1 i promoter to drive I OsRIP1 i in I Nip i , the male sterility phenotype mimicking NIL I -Nip i SP I Dms1 i sp appeared (Figure 1g). Keywords: rice; dominant male sterility; ribosome-inactivating protein; translation inhibition EN rice dominant male sterility ribosome-inactivating protein translation inhibition 1932 1934 3 09/20/23 20231001 NES 231001 Rice ( I Oryza sativa i L.) is a major staple food crop feeding more than half of the world human population. [Extracted from the article]

Meiosis plays an essential role in the production of gametes and genetic diversity of posterities. The normal double-strand break (DSB) repair is vital to homologous recombination (HR) and occurrence of DNA fragment exchange, but the underlying molecular mechanism remain elusive. Here, we characterized a completely sterile Osmfs1 (m ale and f emale s terility 1) mutant which has its pollen and embryo sacs both aborted at the reproductive stage due to severe chromosome defection. Map-based cloning revealed that the OsMFS1 encodes a meiotic coiled-coil protein, and it is responsible for DSB repairing that acts as an important cofactor to stimulate the single strand invasion. Expression pattern analyses showed the OsMFS1 was preferentially expressed in meiosis stage. Subcellular localization analysis of OsMFS1 revealed its association with the nucleus exclusively. In addition, a yeast two-hybrid (Y2H) and pull-down assay showed that OsMFS1 could physically interact with OsHOP2 protein to form a stable complex to ensure faithful homologous recombination. Taken together, our results indicated that OsMFS1 is indispensable to the normal development of anther and embryo sacs in rice. [ABSTRACT FROM AUTHOR]

Selfish genetic elements are pervasive in eukaryote genomes, but their role remains controversial. We show that qHMS7, a major quantitative genetic locus for hybrid male sterility between wild rice (Oryza meridionalis) and Asian cultivated rice (O. sativa), contains two tightly linked genes [Open Reading Frame 2 (ORF2) and ORF3]. ORF2 encodes a toxic genetic element that aborts pollen in a sporophytic manner, whereas ORF3 encodes an antidote that protects pollen in a gametophytic manner. Pollens lacking ORF3 are selectively eliminated, leading to segregation distortion in the progeny. Analysis of the genetic sequence suggests that ORF3 arose first, followed by gradual functionalization of ORF2. Furthermore, this toxin-antidote system may have promoted the differentiation and/ or maintained the genome stability of wild and cultivated rice. [ABSTRACT FROM AUTHOR]

The chloroplast is an important organelle that performs photosynthesis as well as biosynthesis and storage of many metabolites. Aminoacyl-tRNA synthetases (aaRSs) are key enzymes in protein synthesis. However, the relationship between chloroplast development and aaRSs still remains unclear. In this study, we isolated a rice albino 1 (ra1) mutant through methane sulfonate (EMS) mutagenesis of rice japonica cultivar Ningjing 4 (Oryza sativa L.), which displayed albinic leaves in seedling stage due to abnormal chloroplast development. Compared with wild type (WT), ra1 showed significantly decreased levels of chlorophylls (Chl) and carotenoids (Car) in 2-week-old seedlings, which also showed obvious plastidic structural defects including abnormal thylakoid membrane structures and more osmiophilic particles. These defects caused albino phenotypes in seedlings. Map-based cloning revealed that RA1 gene encodes a glycyl-tRNA synthetase (GlyRS), which was confirmed by genetic complementation and knockout by Crispr/Cas9 technology. Sequence analysis showed that a single base mutation (T to A) occurred in the sixth exon of RA1 and resulted in a change from Isoleucine (Ile) to Lysine (Lys). Real-time PCR analyses showed that RA1 expression levels were constitutive in most tissues, but most abundant in the leaves and stems. By transient expression in Nicotiana benthamiana , we found that RA1 protein was localized in the chloroplast. Expression levels of chlorophyll biosynthesis and plastid development related genes were disordered in the ra1 mutant. RNA analysis revealed biogenesis of chloroplast rRNAs was abnormal in ra1. Meanwhile, western blotting showed that synthesis of proteins associated with plastid development was significantly repressed. These results suggest that RA1 is involved in early chloroplast development and establishment of the plastidic ribosome system in rice. • RA1 is a novel gene controlling chlorophyll synthesis and the ribosome system. • Absence of aminoacyl-tRNA synthetases lead to plastid developmental disorders. • Biosynthesis of plastidic ribosomes is severely impaired in the ra1 mutant. • RA1 protein is targeted to the chloroplast. [ABSTRACT FROM AUTHOR]

Hybrid sterility restricts the utilization of superior heterosis of indica - japonica inter-subspecific hybrids. In this study, we report the identification of RHS12 , a major locus controlling male gamete sterility in indica - japonica hybrid rice. We show that RHS12 consists of two genes (iORF3 / DUYAO and iORF4 / JIEYAO) that confer preferential transmission of the RHS12 - i type male gamete into the progeny, thereby forming a natural gene drive. DUYAO encodes a mitochondrion-targeted protein that interacts with OsCOX11 to trigger cytotoxicity and cell death, whereas JIEYAO encodes a protein that reroutes DUYAO to the autophagosome for degradation via direct physical interaction, thereby detoxifying DUYAO. Evolutionary trajectory analysis reveals that this system likely formed de novo in the AA genome Oryza clade and contributed to reproductive isolation (RI) between different lineages of rice. Our combined results provide mechanistic insights into the genetic basis of RI as well as insights for strategic designs of hybrid rice breeding. [Display omitted] • DUYAO - JIEYAO encodes a toxin-antidote system that confers hybrid male sterility • DUYAO interacts with OsCOX11 to trigger mitochondrial malfunction and cytotoxicity • JIEYAO detoxifies DUYAO by rerouting DUYAO to the autophagosome for degradation • DUYAO - JIEYAO forms a natural gene drive system that may promote speciation in rice A cytotoxicity-detoxification gene drive system entailing mitochondria-autophagosome interaction confers hybrid male sterility in rice. [ABSTRACT FROM AUTHOR]

Summary: Indole-3-acetic acid (IAA), the natural auxin in plants, regulates many aspects of plant growth and development. Extensive analyses have elucidated the components of auxin biosynthesis, transport, and signaling, but the physiological roles and molecular mechanisms of auxin degradation remain elusive. Here, we demonstrate that the dioxygenase for auxin oxidation (DAO) gene, encoding a putative 2-oxoglutarate-dependent-Fe (II) dioxygenase, is essential for anther dehiscence, pollen fertility, and seed initiation in rice. Rice mutant lines lacking a functional DAO display increased levels of free IAA in anthers and ovaries. Furthermore, exogenous application of IAA or overexpression of the auxin biosynthesis gene OsYUCCA1 phenocopies the dao mutants. We show that recombinant DAO converts the active IAA into biologically inactive 2-oxoindole-3-acetic acid (OxIAA) in vitro. Collectively, these data support a key role of DAO in auxin catabolism and maintenance of auxin homeostasis central to plant reproductive development. [Copyright &y& Elsevier]