Flower development of Meliosma (Sabiaceae): evidence for multiple origins of pentamery in the eudicots

Flower developmental studies are a complement to molecular phylogenetics and a tool to understand the evolution of the angiosperm flower. Buds and mature flowers of Meliosma veitchiorum, M. cuneifolia, and M. dilleniifolia (Sabiaceae) were investigated using scanning electron microscopy to clarify flower developmental patterns and morphology, to understand the origin of the perianth merism, and to discuss the two taxonomic positions proposed for Sabiaceae, among rosids or in the basal grade of eudicots. Flowers in Meliosma appear pentamerous with two of the five sepals and petals strongly reduced, three staminodes alternating with two fertile stamens opposite the small petals, and a two-carpellate gynoecium. The flower development in Meliosma is spiral without distinction between bracteoles and sepals. Because of this development, sepals, petals, and stamens are almost opposite and not alternating as expected in cyclical pentamerous flowers. In four-sepal flowers the direction of petal initiation is reversed. The symmetry of the flower appears to be transversally zygomorphic, although this is hidden by the almost equal size of the larger petals. Evidence points to a unique pentamerous origin of flowers in Meliosma, and not to a trimerous origin, as earlier suggested, and adds support to multiple origins of pentamery in the eudicots.     

A comparison of venation pattern development in wild type and a homeotic sepaloid petal mutant of Clarkia tembloriensis (Onagraceae)

Vascular system development in sepals, petals, and sepaloid petals was compared in wild-type and crinkled petal mutant plants of Clarkia tembloriensis. Patterns of vascularization in cleared whole mounts were visualized and traced under both brightfield and polarizing illumination. Wild-type sepals exhibited a basipetal pattern of maturation, with tracheary elements maturing relatively rapidly. Mature sepals had three primary veins with numerous secondary veins. In contrast, wild-type petals exhibited an acropetal pattern of maturation, with tracheary elements maturing relatively slowly. The mature petals had only one primary vein with numerous secondary veins. Sepaloid (crinkled) petals combined characteristics of both wild-type sepals and wild-type petals. They exhibited a basipetal pattern of development and a relatively rapid maturation of the tracheary elements characteristic of wild-type sepals. Venation architecture in crinkled petal mutants showed a single primary vein with numerous secondary veins, similar to wild-type petals. The crinkled petal mutant fits the definition of a homeotic mutant in that the petal has assumed characteristics of the sepal. However, homeotic transformation from petal to sepal is incomplete since the crinkled petal still retains many of the characteristics of wild-type petals.     

Non-targeted analysis of spatial metabolite composition in strawberry (Fragariaxananassa) flowers

Formation of flower organs and the subsequent pollination process require a coordinated spatial and temporal regulation of particular metabolic pathways. In this study a comparison has been made between the metabolite composition of individual flower organs of strawberry (Fragaria × ananassa) including the petal, sepal, stamen, pistil and the receptacle that gives rise to the strawberry fruit. Non-targeted metabolomics analysis of the semi-polar secondary metabolites by the use of UPLC-qTOF-MS was utilized in order to localize metabolites belonging to various chemical classes (e.g. ellagitannins, proanthocyanidins, flavonols, terpenoids, and spermidine derivatives) to the different flower organs. The vast majority of the tentatively identified metabolites were ellagitannins that accumulated in all five parts of the flower. Several metabolite classes were detected predominantly in certain flower organs, as for example spermidine derivatives were present uniquely in the stamen and pistil, and the proanthocyanidins were almost exclusively detected in the receptacle and sepals. The latter organ was also rich in terpenoids (i.e. triterpenoid and sesquiterpenoid derivatives) whereas phenolic acids and flavonols were the predominant classes of compounds detected in the petals. Furthermore, we observed extensive variation in the accumulation of metabolites from the same class in a single organ, particularly in the case of ellagitannins, and the flavonols quercetin, kaempferol and isorhamnetin. These results allude to spatially-restricted production of secondary metabolite classes and specialized derivatives in flowers that take part in implementing the unique program of individual organs in the floral life cycle.     

FRL1 is required for petal and sepal development in Arabidopsis

A novel flower mutant, frl1 (frill 1) was isolated in Arabidopsis thaliana. The frl1 mutant has serrated petals and sepals but the other floral and vegetative organs appear to be normal. To analyse the role of the FRL1 gene, morphological, cytological and double mutant analyses were carried out. The frl1 flower had broader petals and sepals as compared with the wild-type. The distal region of frl1 petals contained fewer epidermal cells but their size was variable and generally larger than that in the wild-type. However, no significant difference was found in the basal region. Observations of the early petal development revealed that the morphology of the developing frl1 petal was normal until the middle of stage 9, but the frl1 phenotype became apparent in stages later than 10. Furthermore, larger nuclei with varied sizes were observed in the distal region of frl1 petals, but not in this region in wild-type petals. This strongly suggests that abnormal endo-reduplication had occurred. These observations indicate that the frl1 mutation affects the number of cell divisions and the subsequent cell expansion during the late stage of petal lamina formation, and that FRL1 might be maintaining the mitotic state or suppressing the transition to the endo-reduplication cycle. Double mutants with the homeotic mutants apetala3-1 and agamous showed additive phenotypes. Ectopic petals in the third whorl of fr11 ag flowers were serrated, indicating that the FRL1 gene acts in petal and sepal development in an organ-specific manner.     

Subcellular Localization of Secondary Lipid Metabolites Including Fragrance Volatiles in Carnation Petals

Pulse-chase labeling of carnation (Dianthus caryophyllus L. cv Improved White Sim) petals with [14C]acetate has provided evidence for a hydrophobic subcompartment of lipid-protein particles within the cytosol that resemble oil bodies, are formed by blebbing from membranes, and are enriched in lipid metabolites (including fragrance volatiles) derived from membrane fatty acids. Fractionation of the petals during pulse-chase labeling revealed that radiolabeled fatty acids appear first in microsomal membranes and subsequently in cytosolic lipid-protein particles, indicating that the particles originate from membranes. This interpretation is supported by the finding that the cytosolic lipid-protein particles contain phospholipid as well as the same fatty acids found in microsomal membranes. Radiolabeled polar lipid metabolites (methanol/water-soluble) were detectable in both in situ lipid-protein particles isolated from the cytosol and those generated in vitro from isolated radiolabeled microsomal membranes. The lipid-protein particles were also enriched in hexanal, trans-2-hexenal, 1-hexanol, 3-hexen-1-ol, and 2-hexanol, volatiles of carnation flower fragrance that are derived from membrane fatty acids through the lipoxygenase pathway. Therefore, secondary lipid metabolites, including components of fragrance, appear to be formed within membranes of petal tissue and are subsequently released from the membrane bilayers into the cytosol by blebbing of lipid-protein particles.     

Evolution of petaloid sepals independent of shifts in B-class MADS box gene expression

Attractive petals are an integral component of animal-pollinated flowers and in many flowering plant species are restricted to the second floral whorl. Interestingly, multiple times during angiosperm evolution, petaloid characteristics have expanded to adjacent floral whorls or to extra-floral organs. Here, we investigate developmental characteristics of petaloid sepals in Rhodochiton atrosanguineum, a close relative of the model species Antirrhinum majus (snapdragon). We undertook this in two ways, first using scanning electron microscopy we investigate the micromorphology of petals and sepals, followed by expression studies of genes usually responsible for the formation of petaloid structures. From our data, we conclude that R. atrosanguineum petaloid sepals lack micromorphological characteristics of petals and that petaloid sepals did not evolve through regulatory evolution of B-class MADS box genes, which have been shown to specify second whorl petal identity in a number of model flowering plant species including snapdragon. These data, in conjunction with other studies, suggests multiple convergent pathways for the evolution of showy sepals.     

Ectopic expression of a single homeotic gene, the Petunia gene green petal, is sufficient to convert sepals to petaloid organs.

Genetic studies in Arabidopsis and Antirrhinum showed that petal determination requires the concomitant expression of two homeotic functions, A and B, whereas the A function alone determines sepal identity. The B function is represented by at least two genes. The Petunia homeotic gene green petal (gp) is essential for petal determination as demonstrated by a Petunia gp mutant that has sepals instead of petals. We have used ectopic expression of the gp gene as a tool to study flower development in Petunia. CaMV 35S-gp expression leads to homeotic conversion of sepals into petaloid organs when expressed early in development. This demonstrates that a single homeotic gene is sufficient to induce homeotic conversion of sepals to petals, suggesting that other petal determining genes are regulated in part by ectopically expressed gp. Indeed, two other MADS-box-containing genes, pmads 2 and fbp 1, which show homology to the Antirrhinum B function gene globosa, are activated in the converted petal tissue. Furthermore, our data provide evidence for autoregulation of gp expression in the petaloid tissue and uncover the role of gp in fusion of petal tissues.     

Phyllotaxis and the Initiation of Primordia During Flower Development in Silene

The measured divergence angles between successive primordiain the developing flower were compared with angles expectedon several hypotheses concerning primordial initiation. Theresults lead to the conclusion that the position and sequenceof initiation of the younger sepals is determined by the olderones but that the influence of an older primordium lasts foronly two plastochrons. The petals and carpels are apparentlypositioned by the sepals. The positions of the stamens are consistentwith their king determined by the sepals (antesepalous stamens)or petals (antepctalous stamens), but their sequence of initiationis consistent with its being determined, like the sepals, bythe two youngest primordia. The data indicate that there aretwo sets of factors governing the initiation of the primordiasubsequent to the sepals: one governing the positioning of theprimordia and resembling the factors governing the positionsof axillary buds, and the other governing the sequence of primordiaand resembling the factors which determine the initiation ofleaves. Measurements of the plastochron ratios were used tocalculate the sizes of the sepal, petal and stamen primordiaat initiation. At the moment of initiation the sepal primordiawere about one third, and the petal and stamen primordia aboutone sixth, of the size of the leaf primordia. In its early developmentthe Silene flower therefore resembles a condensed leafy shootwith precocious axillary buds but with primordia which are smallcompared to leaf primordia. Silene coeli-rosa, flower development, primordia, phyllotaxis     

重瓣紫蓝大岩桐组培苗的花同源异型现象（简报）

Six types of floral homeotic variants of in vitro seedlings were observed in doubleflower sinningia. Type I, red and green mosaic petals exist in the outermost whorl of petal-whorls, 2.38%. Type II, the outermost whorl of petal-whorls exhibit green petals with thin yellow edge, 25.0%. Type III, green petals exist in the innermost side of normal red petal whorls, 1.78%. Type IV, multiple whorls of green petals exist in the inner side of normal sepals, no stamen and carpel, 1.67%. Type V, it exhibits duplicated whorls of sepals in the outermost, 7.14%. Type VI, it exists multiple whorls of green sepals, no petal, stamen and carpel, 0.12%. The total percentage of all types of floral homeotic variants is up to 38.1%. The distribution of nodal site of homeotic flowers were analyzed, and the results showed that the homeotic flower occurred mainly at the fourth and fifth nodes.     

基于UPLC-MS/MS技术的代谢组学方法研究麸皮对杨树桑黄代谢的影响

桑黄孔菌属Sanghuangporus是一类具有重要药用价值的大型真菌,目前被国际公认为抗肿瘤效果最好的药用真菌之一。本研究以添加麸皮栽培的杨树桑黄Sanghuangporus vaninii子实体为研究对象,基于液质联用技术的广泛靶向代谢组学研究,从杨树桑黄子实体中检测出355种代谢产物,差异代谢物86种,上调51种,下调35种,主要集中在氨基酸及其衍生物、核苷酸及其衍生物、糖及醇类、脂质、黄酮、生物碱、有机酸和酚酸等。KEGG代谢通路分析结果表明,差异代谢物富集于56条物质代谢通路,差异显著的有7条,分别为泛醌和其他萜类醌生物合成、次级代谢物的生物合成、色氨酸代谢、丙酸代谢、异喹啉生物碱生物合成和酪氨酸代谢。基于UPLC-MS/MS技术对杨树桑黄子实体进行代谢组学测定,确定麸皮的添加能够促进杨树桑黄次级代谢产物的合成和累积,为杨树桑黄的综合评价利用提供参考。     

Are Petals Sterile Stamens or Bracts? The Origin and Evolution of Petals in the Core Eudicots

BACKGROUND: The aim of this paper is to discuss the controversial origins of petals from tepals or stamens and the links between the morphological expression of petals and floral organ identity genes in the core eudicots. SCOPE: I challenge the widely held classical view that petals are morphologically derived from stamens in the core eudicots, and sepals from tepals or bracts. Morphological data suggest that tepal-derived petals have evolved independently in the major lineages of the core eudicots (i.e. asterids, Santalales and rosids) from Berberidopsis-like prototypes, and that staminodial petals have arisen only in few isolated cases where petals had been previously lost (Caryophyllales, Rosales). The clear correlation between continuous changes in petal morphology, and a scenario that indicates numerous duplications to have taken place in genes controlling floral organ development, can only be fully understood within a phylogenetic context. B-gene expression plays a fundamental role in the evolution of the petals by controlling petaloidy, but it does not clarify petal homology. CONCLUSIONS: An increased synorganization of the flower in the core eudicots linked with the establishment of floral whorls restricts the petaloid gene expression to the second whorl, reducing the similarities of petals with tepals from which they were originally derived. An increased flower size linked with secondary polyandry or polycarpelly may lead to a breakdown of the restricted gene expression and a reversal to ancestral characteristics of perianth development. An altered 'sliding boundary' hypothesis is proposed for the core eudicots to explain shifts in petaloidy of the perianth and the event of staminodial petals. The repetitive changes of function in the perianth of the core eudicots are linked with shifts in petaloidy to the outer perianth whorl, or losses of petal or sepal whorls that can be secondarily compensated for by the inclusion of bracts in the flower. The origin and evolution of petals appears to be as complex on a molecular basis as it is from a morphological point of view.     

STUDIES IN THE FLORAL ANATOMY OF CLAYTONIA (PORTULACACEAE)

Claytonia virginica has a regular flower with two sepals, five petals with an equal number of stamens in positions opposite the petals and a many-seeded tricarpellate gynoecium with basal placentation. The flower has been interpreted as uniseriate, the putative sepals as bracts and the corolla as modified calyx lobes. Anatomical and developmental studies were undertaken to find evidence for the existence of vestigial or rudimentary parts whose existence would illuminate the true nature of the flower. Vascular and epidermal anatomy of sepals are both similar to that of leaves. Corolla and androecium develop basipetally and petals and stamens share common vascular traces in the lower part of the receptacle. Thus, in terms of both anatomy and development, evidence supports the conclusion that the perianth is essentially biseriate. Vestigial or rudimentary parts are not present which would alter the manifest design of the mature flower.     

Reactive Oxygen Species and Alternative Respiration in the Developing Flowers of Two Subtropical Woody Plants

Petals, sepals, pistils, and stamens from flowers of two landscape tree species (Elaeocarpus hainanensis Oliv and Michelia alba DC) were analyzed to determine the changes in levels of reactive oxygen species (ROS), lipoxygenase (LOX) activity, and alternative pathway respiration throughout flower development. Histochemical and quantitative analyses revealed that ROS levels differed among tissues and stages of flower development. ROS levels were high in all flower tissues early in development and then declined to low levels late in development. ROS levels were highest in the stamen. In contrast, LOX activity, heat energy evolution, and the percentage of total respiration represented by alternative respiration in M. alba petals increased with flower development. The results suggest that ROS are involved in the growth of various flower tissues at early developmental stages and not only located on the tip site of growing tissues. The reduction in ROS generation later in development is probably due to the significant elevation in alternative respiration. The increase in LOX activity and heat energy evolution might contribute to the formation and release of some aromatic compounds and to flower opening. LOX, however, might not mediate ROS generation in the petal during development.     

刺芹侧耳不同发育时期的转录组差异分析

为了探讨刺芹侧耳子实体生长发育时期的基因表达变化,本文利用高通量测序技术对刺芹侧耳不同发育时期（菌丝期、原基期、子实体时期）进行RNA-Seq分析,在转录水平上解析差异表达基因在刺芹侧耳生长发育过程中的作用和功能。KEGG功能富集显示,菌丝期差异表达基因主要富集在碳代谢和氨基酸代谢中,其中三羧酸循环中编码柠檬酸合酶、乌头酸水合酶、异柠檬酸脱氢酶、琥珀酰辅酶A合成酶、琥珀酸脱氢酶、苹果酸脱氢酶的基因表达量均上调,说明碳代谢和氨基酸代谢是菌丝时期的主要能量来源;原基期上调的差异表达基因主要富集在脂肪酸代谢,其中RT-PCR定量结果显示原基期编码脂肪酸合酶的基因和编码脂酰辅酶A合成酶的基因下调,编码超氧化物酶的基因和编码过氧化氢酶的基因上调,表明脂肪酸代谢和抗氧化酶对刺芹侧耳原基期维持机体的稳定和生物应激方面起着重要作用。子实体时期上调的差异表达基因主要富集在剪接体、类固醇的生物合成以及AMPK信号通路中,说明环境因子对子实体时期有一定的影响。