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- Author or Editor: Xiaoxiao Zhang x
The effects of different pollen sources on fruit and seed characteristics of Paeonia ostii ‘Feng Dan’ were investigated using analysis of three different pollination treatments and pollen sources from fifteen cultivars in two successive years. The results showed that self-pollination decreased fruit setting, the number of seeds per fruit, seed volume, seed and kernel weights, and the linoleic acid (LA) concentration in the seed oil, but increased the concentration of oleic acid (OA) compared with cross-pollination. Among those pollen donors, P. suffruticosa ‘Yinhong Qiaodui’ produced the highest fruit set (87.5%); the lowest fruit set was obtained with P. suffruticosa ‘Mo Run Jue Lun’ (44.33%). The most seeds per fruit were achieved by P. suffruticosa ‘Mochi Jin Hui’. P. suffruticosa ‘Dahong Baozhu’ produced the largest fruit, which contained larger and heaviest seeds. The oil extraction ratio (26% to 31.6%) and the concentration of three major unsaturated fatty acids (UFAs) in seed oil also significantly differed among pollen sources. The content of OA, LA, and α-linolenic acid (ALA) ranged from 13.82 to 24.79, 12.09 to 21.84, and 23.50 to 38.64 g/100 g crude oil, respectively. Overall, pollen source has clear effects on seed yield and even on fatty acid (FA) composition of seed oil in tree peony.
Expansins are proteins that have been reported to contribute to fruit softening. In this study, an expansin gene, CDK-Exp3, was identified from persimmon fruit, and the mRNA accumulation of CDK-Exp3 during postharvest softening was examined using real-time polymerase chain reaction (PCR). Sequence analysis showed that CDK-Exp3 contained a putative open reading frame of 765 bp encoding a polypeptide of 254 amino acid residues, which had all the characteristics of α-expansin. As fruit softened, the expression of CDK-Exp3 increased dramatically within the initial 8-day ripening at 20 °C followed by a gradual decline at the late stages of ripening. The expression of CDK-Exp3 was inhibited by gibberellic acid, and the maximum transcript abundance was delayed by 20 days compared with that of the control fruit. The results suggest that CDK-Exp3 might be closely related to softening of persimmon fruit during postharvest ripening.
Tree peony (Paeonia sp.) is a popular traditional ornamental plant in China. Among the nine wild species, Paeonia rockii displays wide-ranging, deep purple variegation at the base of the petals, whereas Paeonia ostii exhibits purely white petals. Overall, the posttranscriptional regulation involved in tree peony flower opening and pigmentation remains unclear. To identify potential microRNAs (miRNAs) involved in flower variegation, six small RNA libraries of P. ostii and P. rockii petals at three different opening stages were constructed and sequenced. Using Illumina-based sequencing, 22 conserved miRNAs and 27 novel miRNAs were identified in P. rockii and P. ostii petals. Seventeen miRNAs were differentially expressed during flower development, and several putative target genes of these miRNAs belonged to transcription factor families, such as Myb domain (MYB), and basic helix-loop-helix (bHLH) transcription factors. Furthermore, an integrative analysis of the expression profiles of miRNAs and their corresponding target genes revealed that variegation formation might be regulated by miR159c, miR168, miR396a, and novel_miR_05, which target the MYB transcription factors, chalcone synthase (CHS), and ABC transporter. Our preliminary study is the first report of miRNAs involved in Paeonia flower pigmentation. It provides insight regarding the molecular mechanisms underlying the regulation of flower pigmentation in tree peony.