Search

ABSTRACTOil bodies (OBs) are organelles of lipid storage in plants. In order to clarify the properties of OBs development in herbaceous peony (Paeonia lactifloraPall.) seeds, this research had studied anatomical structures, particle size, zeta potential, the stability of OBs and characteristics of oleosin gene (OLE). It showed that OB particle size increased gradually during seed development, OBs accumulated in the endosperm cells, and their zeta potential firstly decreased and then increased. Temperature had not affected the stability of OBs, they could be maintained stably under the conditions of neutral and alkaline pH and less than 50 mM NaCl. Subsequently, P. lactiflora OLEwas isolated, it had 824 bp in full-length and a 435-bp open reading frame encoding 144 amino acids with isoelectric point 9.40, which had three transmembrane domain and did not has a signal peptide, and belonged to the stable protein. Alpha helix was the main part of the secondary structure, no glycosylation site and 14 potential phosphorylation sites were found. Additionally, the express level of OLEinitially increased and then decreased, and reached the highest on 60 days after flowering. These results could contribute to understand the properties of OBs development and characteristics of OLEin P. lactifloraseeds.

microRNAs (miRNAs) play critical regulatory roles in plant growth and development. In the present study, the function of herbaceous peony (Paeonia lactifloraPall.) miR156e-3p in the regulation of color formation has been investigated. Firstly, P. lactifloramiR156e-3p precursor sequence (pre-miR156e-3p) was isolated. Subsequently, the overexpression vector of pre-miR156e-3p was constructed and transformed into Arabidopsis thaliana. Moreover, the medium screening, GUS staining, polymerase chain reaction (PCR) of the GUS region and real-time quantitative PCR (qRT-PCR) of miR156e-3p all confirmed that the purpose gene had been successfully transferred into Arabidopsisplants and expressed, which resulted in apparent purple lateral branches. And this change in color was caused by the improved anthocyanin accumulation. In addition, expression analysis had shown that the level of miR156e-3p transcript was increased, while transcription level of target gene squamosa promoter binding protein-like gene (SPL1), encoding SPLtranscription factor that negatively regulated anthocyanin accumulation, was repressed in miR156e-3p-overexpressing transgenic plants, and its downstream gene dihydroflavonol 4-reductase gene (DFR) that was directly involved in anthocyanin biosynthesis was strongly expressed, which resulted in anthocyanin accumulation of Arabidopsislateral branches. These findings would improve the understanding of miRNAs regulation of color formation in P. lactiflora.

The mechanical strength of inflorescence stems is an important trait in cut flowers. Calcium ions (Ca2+) play a pivotal role in maintaining stem strength, but little is known about the underlying molecular mechanisms. In this study, we treated herbaceous peony (Paeonia lactifloraPall.) with ethyl glycol tetraacetic acid (EGTA), an effective Ca2+chelator, and used morphology indicators, spectroscopic analysis, histochemical staining, electron microscopy, and proteomic techniques to investigate the role of Ca2+in inflorescence stem mechanical strength. The EGTA treatment reduced the mechanical strength of inflorescence stems, triggered the loss of Ca2+from cell walls, and reduced lignin in thickened secondary walls in xylem cells as determined by spectroscopic analysis and histochemical staining. Electron microscopy showed that the EGTA treatment also resulted in significantly fewer xylem cell layers with thickened secondary walls as well as in reducing the thickness of these secondary walls. The proteomic analysis showed 1065 differentially expressed proteins (DEPs) at the full-flowering stage (S4). By overlapping the Kyoto encyclopedia of genes and genomes (KEGG) and gene ontology (GO) analysis results, we identified 43 DEPs involved in signal transduction, transport, energy metabolism, carbohydrate metabolism, and secondary metabolite biosynthesis. Using quantitative real-time polymerase chain reaction (qRT-PCR) analysis, we showed that EGTA treatment inhibited Ca2+sensors and secondary wall biosynthesis-related genes. Our findings revealed that EGTA treatment reduced the inflorescence stem mechanical strength by reducing lignin deposition in xylem cells through altering the expression of genes involved in Ca2+binding and secondary wall biosynthesis.