Seed development in Paeonia ostii (Paeoniaceae), with particular reference to embryogeny.

BACKGROUND: Seeds of Paeonia ostii have been proposed as a source of raw material for the production of edible oil; however, lack of information about the developmental biology of the seeds hampers our ability to use them. Our aim was to investigate development of the seed coat, endosperm and embryo of P. ostii in relation to timing of accumulation of nutrient reserves from pollination to seed maturity. Ovules and developing seeds of P. ostii were collected at various stages of development from zygote to maturity. Seed fresh mass, dry mass, germination, moisture, soluble sugars, starch, protein and oil content were determined. Ontogeny of seeds including embryo, endosperm and seed coat were analyzed histologically. RESULTS: The ovule of P. ostii is anatropous, crassinucellate and bitegmic. The zygote begins to divide at about 5 days after pollination (DAP), and the division is not accompanied by cell wall formation. By 25 DAP, the proembryo begins to cellularize. Thereafter, several embryo primordia appear at the surface of the cellularized proembryo, but only one matures. Endosperm development follows the typical nuclear type. The seed coat is derived from the outer integument. During seed development, soluble sugars, starch and crude fat content increased and then decreased, with maximum contents at 60, 80 and 100 DAP, respectively. Protein content was relatively low compared with soluble sugars and crude fat, but it increased throughout seed development. CONCLUSIONS: During seed development in P. ostii, the seed coat acts as a temporary storage tissue. Embryo development of P. ostii can be divided into two stages: a coenocytic proembryo from zygote (n + n) that degenerates and a somatic embryo from peripheral cells of the proembryo (2n → 2n). This pattern of embryogeny differs from that of all other angiosperms, but it is similar to that of gymnosperms.

Why does only one embryo sac develop in the Paeonia ovule with multiple archesporium?

Structure of the multiple archesporium in an ovule, time and place of archesporial cell differentiation and their developmental potential have not been studied in detail. In Paeonia species supernumerary archesporial cells are formed and differentiate as multiple megasporocytes, but only one embryo sac usually develops into an ovule. The reasons leading to development of one gametophyte and the death of most megasporocytes are unknown. The morphological structure of the multiple archesporium in Paeonia veitchii and P. caucasica was studied using cytoembryological methods. We used staining with aniline blue and fluorescence microscopy for visualization of callose on the megasporocyte walls. All cells of the ovule in investigated Paeonia species are uniform and meristematic at the earliest development stage. The onset of archesporium differentiation correlates with inner integument initiation. The sporogenous complex includes ten to 25 cells which develop asynchronously. The cell located in the central part of the sporogenous complex is differentiated into a megasporocyte earlier than in neighbouring cells. Only this megasporocyte is enveloped in callose; it develops further through to meiosis and forms a female gametophyte. The other megasporocytes degenerate during ovule development. We consider that callose participates in the mechanism of 'lateral inhibition' during megasporocyte maturation. The cell located in the central part of the Paeonia ovule is the first to receive signals that stimulate the onset of megasporogenesis and formation of the callose wall. It is possible that callose participates in blocking of development signals to neighbouring megasporocytes, leading to the arrest of their development.

Physicochemical properties and antioxidant activities of tree peony (Paeonia suffruticosa Andr.) seed protein hydrolysates obtained with different proteases.

The physicochemical and antioxidant properties of tree peony seed protein (TPSP) hydrolysates by Alcalase, Neutrase, Papain, Protamex, and Flavourzyme were investigated in this study. The physicochemical properties were characterized by SDS-PAGE, particle size distribution, fourier transform infrared and fluorescence spectroscopy etc. The antioxidant activities were determined by DPPH radical, ABTS radical, Fe2+ chelating, and reducing power. The results showed five proteases produced hydrolysates with a significantly reduced average particle size, α-helices, and surface hydrophobicity compared to TPSP. Alcalase and Neutrase hydrolysis enhanced the nutritional value of the hydrolysates. Alcalase hydrolysates possessed the highest degree of hydrolysis (27.97%) and lowest molecular weight (<13 kDa) with average particle size (231.33 nm). Alcalase hydrolysate displayed the highest radical scavenging (DPPH IC50 = 0.18 mg/mL, ABTS IC50 = 1.57 mg/mL), Fe2+ chelating activity (IC50 = 0.99 mg/mL), and reducing power (0.594). These results provide the fundamentals for TPSP hydrolysates as antioxidants to be employed in food industry or pharmaceutical industry.

Profiling of neuraminidase inhibitory polyphenols from the seeds of Paeonia lactiflora.

Bacterial neuraminidase (NA) is a lynch pin enzyme in the formation of biofilms. Thus NA continues to be one of the key enzymes targeted by bacterial infection. The purpose of this manuscript is to communicate four new naturally derived inhibitors of neuraminidase (IC50s 3.7-24.4µM). All these active species (1-4) contained a resveratrol chemotype, however resveratrol itself was inactive (IC50>100µM). 1-4 were isolated from the 60% aqueous ethanol extract of seeds of Paeonia lactiflora, which exhibited potent neuraminidase inhibition. Purification of the extracts yielded four chiral polyphenols, suffruticosol A (1), suffruticosol B (2), trans-ε-viniferin (3), and trans-gnetin H (4). Mechanistic analysis of 1-4's inhibition showed that they were all reversible, noncompetitive inhibitors. Trans-ε-viniferin (3) underwent trans-cis isomerization, which led to a reduction in inhibition potency. This correlates with the fact that the cis-isomer is a weaker inhibitor of neuraminidase than the trans-isomer. Importantly, significantly different optical rotations ([α]D) compared to previous reports were found for suffruticosols A (+95 vs -34) and B (+136 vs +13). These two species are the most important standard metabolites in the whole paeoniaceae family and therefore correction of this error is important.

cis-Ampelopsin E, a stilbene isolated from the seeds of Paeonia suffruticosa, inhibits lipopolysaccharide-stimulated nitric oxide production in RAW 264.7 macrophages via blockade of nuclear factor-kappa B signaling pathway.

Stilbenes are a class of compounds that has been reported to inhibit a variety of pathological processes during inflammatory reactions. In this study, cis-ampelopsin E, a stilbene isolated from the seeds of Paeonia suffruticosa, was shown to dose-dependently reduce the nitric oxide (NO) production from lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. The reduction in the nitric oxide release occurred in parallel with the comparable inhibition of inducible nitric oxide synthase (iNOS) enzyme expression, which was achieved by cis-ampelopsin E's suppressive effect on nuclear factor-kappa B (NF-κB) signaling activation. By inhibiting LPS-induced inhibitor kinase (IKKα/ß) phosphorylation, cis-ampelopsin E significantly decreased LPS-induced IκBα phosphorylation, prevented IκBα degradation, and subsequently reduced the translocating of transcription factor p65 into the nucleus. As a result, the LPS-induced upregulation of NF-κB transcriptional activity was efficiently inhibited. Moreover, it is revealed that cis-ampelopsin E inhibited LPS-induced cyclooxygenase-2 (Cox-2) expression, cPLA2 activation and prostaglandin E2 (PGE2) production. These results, taken together, suggested that cis-ampelopsin E might exert potential anti-inflammatory effects via blockage of the NF-κB signaling pathway.

The interplay of pollination, costs of reproduction and plant size in maternal fertility limitation in perennial Paeonia officinalis.

Although several factors can limit female fertility in perennial plants, rarely have they been jointly studied in a single species over several years. In this study we experimentally manipulate seed production and simultaneously analyse the potential contribution of pollen limitation, costs of reproduction and plant size to variation in seed output over a 3-year period in the perennial herb Paeonia officinalis, in southern France. Since this rare species is threatened by forest closure in many sites we also examine the causes of female fertility variation in relation to habitat closure (open habitat vs. woodland). P. officinalis has a partial self-incompatibility system and only very low ability for autonomous self pollination in the absence of pollinators. However, supplementary pollination of individual plants in three consecutive years did not significantly increase seed production above natural levels. Forest closure was associated with a decline in ovule and seed production, which again was not due to pollen limitation since supplementary pollination had no significant effect on seed set in the woodland habitat. Comparison of the maternal fertility of plants which were previously excluded from reproduction with those which were hand pollinated to maximise seed set in two previous years produced no evidence that seed production in year three is limited by costs associated with prior reproduction. Likewise, flowering probability was not related to prior seed production but was however positively related to plant size. The absence of any influence of pollen limitation or prior reproduction on seed production suggests that sub-maximal seed production in long-lived perennial herbs may be part of a size-dependent strategy that maximises life-time seed production and fitness without compromising survival.

Cryopreservation of somatic embryos of the herbaceous peony (Paeonia lactiflora Pall.) by air drying.

This study was carried out to establish a suitable method for the cryopreservation of somatic embryos of the herbaceous peony. The somatic embryos were obtained from cotyledon and anther cultures on a MS medium supplemented with abscisic acid (ABA) and phenylacetic acid (PAA), respectively. The frequency of somatic embryo formation was the greatest (61%) from the cotyledons cultured on a MS medium supplemented with 1.0 mg l(-1) of ABA. Embryos were also obtained directly from anthers cultured on a MS medium with or without 2.0 mg l(-1) of PAA. For the cryopreservation of peony somatic embryos, the embryos were dried under a stream of sterile air and frozen by immersion in liquid nitrogen. Thawed embryos were germinated into plantlets after placing on a medium containing 0.3 mg l(-1) of gibberellic acid (GA(3)). The frequency of the post-thaw regrowth of cryopreserved somatic embryos was related to their size and desiccation time, the latter ranging from 0 to 2 h. When the somatic embryos were desiccated for 1 h, the frequency of post-thaw regrowth was greater than 66%. The frequency of post-thaw regrowth of the cryopreserved somatic embryos from anthers and cotyledon tissues was generally high when they were 2-3 mm in size. Desiccation may be a suitable method for the cryopreservation of somatic embryos of the herbaceous peony.