Single-cell RNA sequencing of meiocytes and microspores reveals the involvement of the Rf4 gene in redox homeostasis of CMS-C maize

Normal microsporogenesis is determined by both nuclear and mitochondrial genes. In maize C-type cytoplasmic male sterility, it is unclear how the development of meiocytes and microspores is affected by the mitochondrial sterility gene and the nuclear restorer gene. In this study, we sequenced the transcriptomes of single meiocytes(tetrad stage) and early mononucleate microspores from sterile and restorer lines. The numbers of expressed genes varied in individual cells and fewer than half of the expressed genes were common to the same cell types. Four comparisons revealed 3379 differentially expressed genes(DEGs), with 277 putatively associated with mitochondria, 226 encoding transcription factors,and 467 possibly targeted by RF4. KEGG analysis indicated that the DEGs in the two lines at the tetrad stage were involved predominantly in carbon metabolism and in amino acid biosynthesis and metabolism, whereas the DEGs during the transition from the tetrad stage to the early mononucleate stage were associated mostly with regulation of protein metabolism, fatty acid metabolism, and anatomical structure morphogenesis. Thus, meiocyte and microspore development was affected by the surrounding cells and the restorer gene, and the restorer gene helped restore the redox homeostasis of microspores and the normal cellular reconstruction during the transition.

Tilting objects on tubular weighted projective lines: A cluster tilting approach

Using the cluster tilting theory,we investigate the tilting objects in the stable category of vector bundles on a weighted projective line of weight type(2,2,2,2).More precisely,a tilting object consisting of rank-two bundles is constructed via the cluster tilting mutation.Moreover,the cluster tilting approach also provides a new method to classify the endomorphism algebras of the tilting objects in the category of coherent sheaves and the associated bounded derived category.

The chimeric gene atp6c confers cytoplasmic male sterility in maize by impairing the assembly of the mitochondrial ATP synthase complex

Cytoplasmic male sterility(CMS)is a powerful tool for the exploitation of hybrid heterosis and the study of signaling and interactions between the nucleus and the cytoplasm.C-type CMS(CMS-C)in maize has long been used in hybrid seed production,but the underlying sterility factor and its mechanism of action remain unclear.In this study,we demonstrate that the mitochondrial gene atp6c confers male sterility in CMS-C maize.The ATP6C protein shows stronger interactions with ATP8 and ATP9 than ATP6 during the assembly of F1F0-ATP synthase(F-type ATP synthase,ATPase),thereby reducing the quantity and activity of assem-bled F_(1)F_(o)-ATP synthase.By contrast,the quantity and activity of the F1'component are increased in CMS-C lines.Reduced F1F0-ATP synthase activity causes accumulation of excess protons in the inner membrane space of the mitochondria,triggering a burst of reactive oxygen species(ROS),premature programmed cell death of the tapetai cells,and pollen abortion.Collectively,our study identifies a chimeric mitochondrial gene(ATP6C)that causes CMS in maize and documents the contribution of ATP6C to F1F0-ATP synthase assembly,thereby providing novel insights into the molecular mechanisms of male sterility in plants.

The main restorer Rf3 of maize S type cytoplasmic male sterility encodes a PPR protein that functions in reduction of the transcripts of orf355

Dear Editor,Male sterile lines,especially cytoplasmic male sterile(CMS)lines,are extensively used in commercial hybrid seed production.Therefore a better understanding of the genetic basis of fertility restoration for CMS is important for the utility of heterosis in crops.In general,restorer of fertility(Rf)is controlled by one or two major genomic genes,and most of the Rf genes encode pro-teins containing P type pentatricopeptide repeat(PPR)motifs(Wang et al.,2006;Hu et al.,2012;Tang et al.,2014;Liu et al.,2016).S type CMS(CMS-S)is the main type of maize CMS with wide cytoplasmic sources,and orf355-orf77 in CMS-S was associated with male sterility(Zabala et al.,1997).The 5'stem-loop of the transcript of orf355-orf77 was thought to be associ-ated with its stability(Xiao et al.,2006).Recently,Xiao et al.(2020)confirmed that orf355 is the causal gene of CMS-S.Rf3,the main restorer of CMS-S,has been mapped to the long arm of chromosome 2 for a long time(Laughnan and Gabay,1978).Since then,great efforts have been made on genetic mapping and cloning of this gene(Xu et al.,2009).