Project description:‘Kuerlexiangli’ (Pyrus sinkiangensis Yu) is an important market pear in China. The shape and quality of the fruit is negatively affected by the presence of a persistent calyx. Here, to explore the molecular mechanism of calyx abscission, we designed an experiment to compare protein expression at two critical stages of the calyx abscission process under three treatments: a calyx abscising treatment (6000 × Flusilazole + 300 × PBO), a calyx persisting treatment (50 mg L−1 GA3), and a water control. We investigated the collected protein fragments using isobaric tags for relative and absolute protein quantitation (iTRAQ) to identify candidate proteins and perform relative quantification. We identified 378,078 spectra and 3,873 proteins, of which there were 2,371 differentially abundant proteins (DAPs) having Gene Ontology terms and associating with 124 defined pathways from the Kyoto Encyclopedia of Genes and Genomes. The DAPs that were correlated with calyx abscission were mainly those known to be involved in photosynthesis, plant hormone signal transduction, cell-wall modification, and carbohydrate metabolism. Quantitative real-time PCR was used to confirm the results of the digital transcript abundance measurements. Among the isolated candidate proteins, polygalacturonase and chitinase appear to play key roles during the process of calyx abscission. We identified candidate proteins that exhibit highly dynamic expression changes during the calyx abscission progress. These proteins are potential targets for future functional identification and should be valuable to explore the mechanism of the calyx abscission, and finally for the development of a method for inducing calyx abscission in fruit production based on the use of small molecules.
Project description:In many plant species, flower stigma secretions are important in early stages of sexual reproduction. Previous chemical analysis and proteomic characterization of these exudates provided insights into their biological function. Nevertheless, the presence of nucleic acids in the stigma exudates has not been previously reported. Here we studied the stigma exudates of Pyrus communis, Pyrus pyrifolia and Pyrus syriaca, and showed them to harbor extracellular RNAs of various sizes. RNA sequencing revealed, for the first time, the presence of known Rosaceae mature micro-RNAs (miRs), also abundant in the stigma source tissue. Predicted targets of the exudate miRs in the Arabidopsis thaliana genome include genes involved in various biological processes. Several of these genes are pollen transcribed, suggesting possible involvement of exudate miRs in transcriptional regulation of the pollen. Moreover, extracellular miRs can potentially act across kingdoms and target genes of stigma interacting organisms/microorganisms, thus opening novel applicative avenues in HortSciences.
Project description:Optimal glucose metabolism is central to the growth and development of cells. In microbial eukaryotes, carbon catabolite repression (CCR) mediates the preferential utilization of glucose, primarily by repressing alternate carbon source utilization. In fission yeast, CCR is mediated by transcriptional repressors Scr1 and the Tup/Ssn6 complex, with the Rst2 transcription factor important for activation of gluconeogenesis and sexual differentiation genes upon derepression. Through genetic and genome-wide methods, this study aimed to comprehensively characterize CCR in fission yeast by identifying the genes and biological processes that are regulated by Scr1, Tup/Ssn6 and Rst2, the core CCR machinery. The transcriptional response of S. pombe to glucose-sufficient or glucose-deficient growth conditions in wild type and CCR mutant cells was determined by RNA-seq and ChIP-seq. Scr1 was found to regulate genes involved in carbon metabolism, hexose uptake, gluconeogenesis and the TCA cycle. Surprisingly, a role for Scr1 in the suppression of sexual differentiation was also identified, as homothallic scr1 deletion mutants showed ectopic meiosis in carbon and nitrogen rich conditions. ChIP-seq characterised the targets of Tup/Ssn6 and Rst2 identifying regulatory roles within and independent of CCR. Finally, a subset of genes bound by all three factors was identified, implying that regulation of certain loci may be modulated in a competitive fashion between the Scr1, Tup/Ssn6 repressors and the Rst2 activator. By identifying the genes directly and indirectly regulated by Scr1, Tup/Ssn6 and Rst2, this study comprehensively defined the gene regulatory networks of CCR in fission yeast and revealed the transcriptional complexities which govern this system.