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.

Seed Proteomic Profiles of Three Paeonia Varieties and Evaluation of Peony Seed Protein as a Food Product

Peony (Paeonia) has high ornamental, edible, and medicinal values. In order to distinguish seeds varieties, describe the proteomic profiles correlated with stress tolerance, and evaluate peony seed protein (PSP) as a functional food product, we characterized the seed protein profiles of these three species and their glucosidase inhibition activities. Results showed that the intensity of protein bands in sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and specific protein ID (especially for specifically expressed proteins (SEPs)) was effective to distinguish these peony seed varieties. Proteomic analysis of the three species showed that P. ostii "Fengdan" has heat and pathogen tolerance-related proteins, while P. rockii has higher content of proteins related to cold resistance, which were all highly consistent with their adaptation of heat or cold habitat. Moreover, stress-related proteins were also accumulated in P. lactiflora Pall "Hangshao" seeds, showing its potential for stress resistance. Further protein analysis showed that the primary composition of PSP was albumin and globulin. And the solubility of PSP was good. Furthermore, PSP also showed high glucosidase inhibition activity, indicating that PSP might have some potential function for the remission of hyperglycemia. And P. ostii "Fengdan" seeds may be a better source for protein production than seeds of the other two species in terms of protein solubility and the content of total protein, albumin, and globulin. In addition, an optimal protocol of microwave-assisted alkali extraction was developed to produce PSP. In conclusion, the evaluated stress-related proteins in three peony seed species by proteomic analysis quite agreed with their adaptation of heat or cold stress; proteomics could also be a very useful tool for distinguishing species in the production; and peony seeds may be a good source for protein production.

Evaluating the Comprehensive Performance of Herbaceous Peonies at low latitudes by the Integration of Long-running Quantitative Observation and Multi-Criteria Decision Making Approach

Enlarging the planting area of economic plants, such as the "Southward Planting of Herbaceous Peony" (Paeonia lactiflora. Pall), is significant for improving people's lives. Peony is globally known as an ornamental because of gorgeous flowers and is mainly cultivated in the temperate regions with relatively cool and dry climates in the Northern Hemisphere. Promoting the landscape application of peony to the lower latitude regions is difficult because of the hot-humid climate. In this study, 29 northern peony cultivars and a unique Chinese southern peony, 'Hang Baishao', were introduced to Hangzhou, located in the central subtropics. Annual growth cycles, resistances and dormancy durations were measured, and crossbreeding between the southern and northern peonies was performed for six years, from 2012 to 2017. Based on data collected from the long-running quantitative observation (LQO), a multi-criteria decision making (MCDM) system was established to evaluate the comprehensive planting performance of these 30 cultivars in the central subtropics. 'Qihua Lushuang', 'Hang Baishao' and 'Meiju' were highly recommended, while 'Zhuguang' and 'Qiaoling' were scarcely recommended for the Hangzhou landscape. This study highlights the dependability and comprehensiveness of integrating the LQO and MCDM approaches for evaluating the introduction performance of ornamental plants.

Comparative transcriptome and coexpression network analysis of carpel quantitative variation in Paeonia rockii

BACKGROUND

Quantitative variation of floral organs in plants is caused by an extremely complex process of transcriptional regulation. Despite progress in model plants, the molecular mechanisms of quantitative variation remain unknown in woody flower plants. The Paeonia rockii originated in China is a precious woody plant with ornamental, medicinal and oil properties. There is a wide variation in the number of carpel in P. rockii, but the molecular mechanism of the variation has rarely been studied. Then a comparative transcriptome was performed among two cultivars of P. rockii with different development patterns of carpel in this study.

RESULTS

Through the next-generation and single-molecule long-read sequencing (NGS and SMLRS), 66,563 unigenes and 28,155 differentially expressed genes (DEGs) were identified in P. rockii. Then clustering pattern and weighted gene coexpression network analysis (WGCNA) indicated that 15 candidate genes were likely involved in the carpel quantitative variation, including floral organ development, transcriptional regulatory and enzyme-like factors. Moreover, transcription factors (TFs) from the MYB, WD, RING1 and LRR gene families suggested the important roles in the management of the upstream genes. Among them, PsMYB114-like, PsMYB12 and PsMYB61-like from the MYB gene family were probably the main characters that regulated the carpel quantitative variation. Further, a hypothetical model for the regulation pattern of carpel quantitative variation was proposed in which the candidate genes function synergistically the quantitative variation process.

CONCLUSIONS

We present the high-quality sequencing products in P. rockii. Our results summarize a valuable collective of gene expression profiles characterizing the carpel quantitative variation. The DEGs are candidate for functional analyses of genes regulating the carpel quantitative variation in tree peonies, which provide a precious resource that reveals the molecular mechanism of carpel quantitative variation in other woody flower crops.

Elucidation of the mechanism of reflowering in tree peony (Paeonia suffruticosa) 'Zi Luo Lan' by defoliation and gibberellic acid application

In this study, the reflowering mechanism of tree peony (Paeonia suffruticosa 'Zi Luo Lan') after defoliation and gibberellic acid (GA) application (autumn-flowering treatment) was investigated by monitoring the morphological changes, measuring the endogenous GA₃ and abscisic acid (ABA) contents, and determining the expression patterns of six GA- and two ABA-related genes. The results show that autumn-flowering treatment induced tree peony reflowering in autumn, which was accompanied by nutrient absorption in buds. The application of exogenous GA₃ induced a simultaneous increase in GA₃ and decrease in ABA levels, suggesting that the high ratios of GA₃/ABA may play a key role in inducing tree peony reflowering. RT-qPCR analysis shows that PsCPS and PsGA2ox were significantly induced and inhibited by GA₃ application, respectively, which supports the hypothesis that GA₃ treatment induces endogenous GA₃ production. In addition, GA₃ treatment inhibited the expression of the PsGID1c, but its effect on PsGAI1 was limited, whereas the expression of PsGAMYB could be GA- or ABA-related. Furthermore, autumn-flowering treatment significantly inhibited the expression of PsNCED and PsbZIP, which coincides with the observed changes in ABA levels. Therefore, we postulate that autumn-flowering treatment induces tree peony reflowering by inhibiting the function of ABA accumulation and signaling.

Identification and comparative profiling of miRNAs in herbaceous peony (Paeonia lactiflora Pall.) with red/yellow bicoloured flowers

Herbaceous peony (Paeonia lactiflora Pall.) is popular worldwide because of its gorgeous flower colour, and the yellow flower is the rarest. However, its mechanism of yellow formation is still unexplored from the post-translational level. In this study, the anatomy of the petal, cell sap pH and metal elements were investigated in bicoloured flower cultivar 'Jinhui' with red outer-petal and yellow inner-petal, and the yellow formation was influenced by the anatomy of petal, while not by the cell sap pH and metal elements. Subsequently, microRNAs sequencing (miRNA-seq) was used to identify small RNAs (sRNAs). A total of 4,172,810 and 3,565,152 specific unique sRNAs were obtained, 207 and 204 conserved miRNAs and 38 and 42 novel miRNAs were identified from red outer-petal and yellow inner-petal, respectively, which were confirmed by subcloning. Among these miRNAs, 163 conserved and 28 novel miRNAs were differentially expressed in two wheel of petals. And 5 differentially expressed miRNAs and their corresponding target genes related to yellow formation were screened, and their dynamic expression patterns confirmed that the yellow formation might be under the regulation of miR156e-3p-targeted squamosa promoter binding protein-like gene (SPL1). These results improve the understanding of miRNA regulation of the yellow formation in P. lactiflora.

[Comparative study of biological characters and paeoniflorin content of wild and asexual cultivated Paeonia lactiflora growing at Duolun county, Inner Mongolia]

This study aims to investigate whether the cultivation peony, can take the place of wild herbaceous peony by comparing the biological traits and paeoniflorin content between them. The result showed that the biomass of the stem, leaf, crown, fleshy root and fine root of wild plants were all smaller than that of bud asexual cultivated plants, while there was no significant differences in below-ground and aboveground biomass ratio between these two plants. The stele diameter, the proportion of stele, and the ratio of stele diameter to cortex thickness of wild plants were significantly higher than that of bud asexual cultivated plants, while the cortex thickness and the proportion of cortex were significantly smaller than bud asexual cultivated plants. Although the biological traits of bud asexual cultivated plants have changed significantly, the paeoniflorin content in fleshy roots has no significant difference between wild and bud asexual cultivated plants. Therefore, it is feasible to use the bud asexual cultivation to the conservation and large-scale cultivation of Paeonia laciflora, which is an endangered species.

Transcriptome sequencing of a chimaera reveals coordinated expression of anthocyanin biosynthetic genes mediating yellow formation in herbaceous peony (Paeonia lactiflora Pall.)

BACKGROUND

Herbaceous peony (Paeonia lactiflora Pall.) is a traditional flower in China and a wedding attractive flower in worldwide. In its flower colour, yellow is the rarest which is ten times the price of the other colours. However, the breeding of new yellow P. lactiflora varieties using genetic engineering is severely limited due to the little-known biochemical and molecular mechanisms underlying its characteristic formation.

RESULTS

In this study, two cDNA libraries generated from P. lactiflora chimaera with red outer-petal and yellow inner-petal were sequenced using an Illumina HiSeq™ 2000 platform. 66,179,398 and 65,481,444 total raw reads from red outer-petal and yellow inner-petal cDNA libraries were generated, which were assembled into 61,431 and 70,359 Unigenes with an average length of 628 and 617 nt, respectively. Moreover, 61,408 non-redundant All-unigenes were obtained, with 37,511 All-unigenes (61.08%) annotated in public databases. In addition, 6,345 All-unigenes were differentially expressed between the red outer-petal and yellow inner-petal, with 3,899 up-regulated and 2,446 down-regulated All-unigenes, and the flavonoid metabolic pathway related to colour development was identified using the Kyoto encyclopedia of genes and genomes database (KEGG). Subsequently, the expression patterns of 10 candidate differentially expressed genes (DEGs) involved in the flavonoid metabolic pathway were examined, and flavonoids were qualitatively and quantitatively analysed. Numerous anthoxanthins (flavone and flavonol) and a few anthocyanins were detected in the yellow inner-petal, which were all lower than those in the red outer-petal due to the low expression levels of the phenylalanine ammonialyase gene (PlPAL), flavonol synthase gene (PlFLS), dihydroflavonol 4-reductase gene (PlDFR), anthocyanidin synthase gene (PlANS), anthocyanidin 3-O-glucosyltransferase gene (Pl3GT) and anthocyanidin 5-O-glucosyltransferase gene (Pl5GT).

CONCLUSION

Transcriptome sequencing (RNA-Seq) analysis based on the high throughput sequencing technology was an efficient approach to identify critical genes in P. lactiflora and other non-model plants. The flavonoid metabolic pathway and glucide metabolic pathway were identified as relatived yellow formation in P. lactiflora, PlPAL, PlFLS, PlDFR, PlANS, Pl3GT and Pl5GT were selected as potential candidates involved in flavonoid metabolic pathway, which inducing inhibition of anthocyanin biosynthesis mediated yellow formation in P. lactiflora. This study could lay a theoretical foundation for breeding new yellow P. lactiflora varieties.

Effects of shade on plant growth and flower quality in the herbaceous peony (Paeonia lactiflora Pall.)

Herbaceous peony (Paeonia lactiflora Pall.) is an important ornamental plant used in urban green spaces, but little is known about whether it can grow in a shaded environment or understory. In this study, effects of shade on plant growth and flower quality in the herbaceous peony were investigated. The results showed that P. lactiflora morphology parameters, including plant height, leaf number, stem diameter, branch number, node number and plant crown width, were higher in plants grown with sun exposure compared to those grown in shade; however, opposite trends were observed for the top and middle leaf areas of the plant. Compared with sun exposure, shade decreased P. lactiflora photosynthetic capacity, light saturation point (LSP) and light compensation point (LCP) and increased the apparent quantum yield (AQY), mainly due to declined stomatal conduction (Gs). These decreases caused the soluble sugar, soluble protein and malondialdehyde (MDA) contents to decline, which led to delayed initial flowering date, prolonged flowering time, reduced flower fresh weight, increased flower diameter and faded flower color. Through cloning and expression analysis of anthocyanin biosynthetic genes, we determined that the fading of flower color was the result of reduced anthocyanin content, which was caused by the combined activity of anthocyanin biosynthesis genes and, in particular, of the upstream phenylalanine ammonialyase gene (PlPAL) and chalcone synthase gene (PlCHS). These results could provide us with a theoretical basis for further application of P. lactiflora in the greening of urban spaces and an understanding of the mechanisms behind the changes induced by shade.

[Comparative study of plant morphological characteristics and photosynthetic physiological characteristics of wild and cultivated Paeonia lactiflora]

OBJECTIVE

The aim of this study was to compare the plant morphological characteristics and photosynthetic physiological characteristics of Paeonia Radix Rubra and Paeonia Radix Alba, and find evidence of whether there are intraspecific variations of Paeonia lactiflora.

METHOD

With wild and cultivated P. lactiflora of the roots as asexual reproduction materials for cultivation experiment, morphological index, photosynthetic parameters and photosynthetic pigment content were measured.

RESULT

In the 9 of morphological characteristics between wild and cultivated P. lactiflora, the number of leaf, blade length, the width of leaf and the length of top leaf showed a significant difference. The variances within wild P. lactiflora group were big than those within cultivated P. lactiflora in 8 of morphological characteristics. In photosynthetic physiological characteristics, wild P. lactiflora were significantly higher than cultivated P. lactiflora in Max. net photosynthetic rate (P(max)), light compensation point (LCP), light saturation point(LSP), CO2 saturation point (CSP) and CO2 saturated P(n) (P(m)). And significantly lower than cultivated P. lactiflora in maximum net photosynthetic rate (P(max)), light compensation point (LCP), light in apparent quantum yield (AQY), CO2 compensation point (CCP), carboxylation efficiency (CE) and photosynthetic pigment content.

CONCLUSION

Wild and cultivated P. lactiflora have significant difference in morphological characteristics of leaf and photosynthetic physiological characteristics.

[Comparative research on pharmacognostic characteristics and microscopic characteristics of Radix Paeoniae Rubra from different areas]

OBJECTIVE

To compare pharmacognostic characteristics and microscopic characteristics of Radix Paeoniae Rubra (chishao) from different areas.

METHOD

Pharmacognostic characteristics and microscopic characteristics of Radix Paeoniae Rubra were compared by microscope count methods.

RESULT

Chishao in duolun was more straighter and longer, cortex with a set of closely spaced rill, peel off easily, pink section, etc. The wild chishao were different from the cultivated chishao on pharmacognostic characteristics and microscopic characteristics, such as appearance shape, smell, vessel arrangement, and number of crystal and starch in unit area.

CONCLUSION

Chishao in duolun were different form others, appearance shape, wood fiber, difference of appearance shape, vessel arrangement, and number of crystal and starch in unit area can be used as identificatin feature of the wild chishao and the cultivated chishao.

[Unusual alternations of floral organs in Paeonia: structure and possible mechanism of formation]

Morphological analysis of flowers was carried out in Paeonia cultivars. Some unusual alternations of floral organs were described: sepal-(petal-stamen) x N-carpel, where 2 < or = n < or = 4 (appearance of an additional zone of petal and stamen formation in the medial flower part). The identity of floral organs was not affected in the flowers with this unusual alternation. It was shown on the basis of mathematical simulation of the genes responsible for flower development that these alternations may be determined by increased pool of stem cells, which may lead to delayed termination of flower development.

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.

[Study on the original plants and macroscopic characters of Radix Paeoniae]

OBJECTIVE

For the identification of botanical origin and macroscopic characters of Radix Paeoniae.

METHODS

Different types of original plant and crude of Radix Paeoniae samples were collected from 10 main producing areas.

RESULTS

By taxonomical and morphological researches, Paeonia lactiflora and P. lactiflora var. trichocarpa could be identified.

CONCLUSION

The root of P. lactiflora is cylindrical, pale white to reddish brown in surface color, with longitudinal furrows, flat borken section, with radial rows in xylem elements, sour taste. While the root of the variety can be differ from its irregular-cylindrical shape, brownish surface, floury transverse section and sweet taste.

Sexual allocation in single-flowered hermaphroditic individuals in relation to plant and flower size

Gender expression in hermaphroditic plant species usually departs from strict equisexuality. Study of those departures can aid understanding of non hermaphroditic breeding systems and prevalence of hermaphroditism within angiosperms. Plant size is one of the most studied factors in relation to gender modification. We studied variation in gender expression in the hermaphroditic, mostly single-flowered Paeonia cambessedesii. We separately studied gender modification with increasing plant and flower size using a variety of currencies: number of ovules and stamens, dry mass, N and P. Flower size and number of floral structures (petals, stamens, carpels, and ovules) increased with plant size. Number of ovules increased more rapidly with increasing plant size than number of stamens, indicating a bias towards femaleness with increasing plant size. A similar pattern was found when regressing number of stamens and number of seeds against plant size. Number of floral structures increased with increasing flower mass, but no significant difference was found between stamens and ovules in their rate of increase. Thus, gender modification at plant level was not consistent with patterns at flower level. No differential allocation to stamens vs gynoecium, or sexual structures vs petals was found when using dry mass, N or P as currencies. However, a disproportionate increase in female allocation was found when number of structures was utilised as currency. Study of size-dependent gender expression will benefit from contrast of results obtained using several analysis levels and allocation currencies.