A plea for biological descriptions: the case of reproduction biology

Molecular characterization, ultrastructure, and transovarial transmission of Tremblaya phenacola in six mealybugs of the Phenacoccinae subfamily (Insecta, Hemiptera, Coccomorpha) Abstract Mealybugs (Hemiptera, Coccomorpha: Pseudococcidae) are plant sap-sucking insects which require close association with nutritional microorganisms for their proper development and reproduction. Here, we present the results of histological, ultrastructural, and molecular analyses of symbiotic systems of six mealybugs belonging to the Phenacoccinae subfamily: Phenacoccus aceris, Rhodania porifera, Coccura comari, Mirococcus clarus, Peliococcus calluneti, and Ceroputo pilosellae. Molecular analyses based on bacterial 16S rRNA genes have revealed that all the investigated species of Phenacoccinae are host to only one type of symbiotic bacteria—a large pleomorphic betaproteobacteria—Tremblaya phenacola. In all the species examined, bacteria are localized in the specialized cells of the host-insect termed bacteriocytes and are transovarially transmitted between generations. The mode of transovarial transmission is similar in all of the species investigated. Infection takes place in the neck region of the ovariole, between the tropharium and vitellarium. The co-phylogeny between mealybugs and bacteria Tremblaya has been also analyzed.

Comparative studies on structure of the floral nectaries and the abundance of nectar production of Prunus laurocerasus L. Abstract There is very scanty information concerning the floral nectary structure and nectar secretion in Prunus laurocerasus L. Therefore, the aim of the study was to determine the micromorphology, anatomy and ultrastructure of nectaries; the abundance of nectar production; and the quantitative and qualitative composition of sugars contained in the nectar of two P. laurocerasus cultivars: ‘Schipkaensis’ and ‘Zabeliana’. The nectary structure was studied using light, fluorescence, scanning and transmission electron microscopy techniques. The nectar sugars were analysed with HPLC. The ‘Schipkaensis’ had longer inflorescences with a larger number of flowers and a longer perianth than ‘Zabeliana’. The micromorphological structure of the nectaries in ‘Schipkaensis’ exhibited denser (approx. 39%) and larger (approx. 50%) stomata and thicker (approx. 13%) cuticular striae forming wider bands (approx. 26%) than in ‘Zabeliana’. The results provide new data on the micromorphology, anatomy and ultrastructure of these floral nectaries. Nectary cuticle ornamentation as well as the size, type and density of stomata and stomatal complex topography can have a diagnostic value in Prunus. The nectar sugar weight indicates a significant apicultural value of the cherry laurel, especially in the case of ‘Schipkaensis’. Cherry laurel is an entomophilous species recommended for cultivation in nectariferous zones and insect pollinator refuges; however, climatic conditions eliminating the invasiveness of these plants should be considered.

Elevated gibberellin altered morphology, anatomical structure, and transcriptional regulatory networks of hormones in celery leaves Abstract Gibberellins (GAs), as one of the important hormones in regulating the growth and development of higher plants, can significantly promote cell elongation and expansion. Celery is a widely grown leafy vegetable crop with rich nutritional value. However, the effect of gibberellins on celery leaves is unclear. In this paper, the celery variety “Jinnan Shiqin” plants were treated with gibberellic acid (GA3) and paclobutrazol (PBZ, a gibberellin inhibitor). Our results showed that GA3 treatment promoted the growth of celery leaves and caused lignification of celery leaf tissue. In addition, the transcript levels of genes associated with gibberellins, auxin, cytokinins, ethylene, jasmonic acid, abscisic acid, and brassinolide were altered in response to increased or decreased exogenous gibberellins or inhibitor. GA3 may regulate celery growth by interacting with other hormones through crosstalk mechanisms. This study provided a reference for further study of the regulation mechanism of gibberellins metabolism, and exerted effects on understanding the role of gibberellins in the growth and development of celery.

Insights into physiological responses of mosses Physcomitrella patens and Pohlia drummondii to lichen secondary metabolites Abstract It is widely accepted that allelopathy among mosses and lichens do exist due to its similar ecological needs, though it is rarely documented. With an aim to test whether there is an effect of allelochemicals to mosses, we grow axenically two moss species (namely Physcomitrella patens and Pohlia drummondii) in controlled conditions and use them to test the effect of lichen Pseudevernia furfuracea acetone extracts containing active compounds: atranorin, chloratranorin, and physodic acid. The photosynthesis value and the biochemical parameters were measured to detect changes in moss organisms upon application of different concentration of lichen extract. The results obtained clearly showed that both moss species reacted to allelochemicals applied in test but to different extent. This suggests that tested moss species have various patterns on reaction to allelochemicals, and that the process of allelopathy is rather a recently coevolving one, than pre-defined. The lichen secondary metabolites are allelochemicals effective also to moss species that are not selected lichen cohabitants.

Mitochondrial numbers increase during glucose deprivation in the slime mold Physarum polycephalum Abstract Glucose deprivation in the slime mold Physarum polycephalum leads to a specific morphotype, a highly motile mesoplasmodium. We investigated the ultrastructure of both mesoplasmodia and non-starved plasmodia and found significantly increased numbers of mitochondria in glucose-deprived mesoplasmodia. The volume of individual mitochondria was the same in both growth forms. We conjecture that the number of mitochondria correlates with the metabolic state of the cell: When glucose is absent, the slime mold is forced to switch to different metabolic pathways, which occur inside mitochondria. Furthermore, a catabolic cue (such as AMP-activated protein kinase (AMPK)) could stimulate mitochondrial biogenesis.

Spermiogenesis of the hangingfly Terrobittacus implicatus (Huang and Hua) (Mecoptera: Bittacidae) Abstract The structure of spermatozoa is able to provide valuable characters in resolving phylogenic relationships in Metazoa, especially in insects. Such data, however, are greatly deficient in Mecoptera. Here, we studied the spermiogenesis and ultrastructure of sperm in the hangingfly Terrobittacus implicatus (Huang and Hua) using transmission electron microscopy. The results show that the spermatogenesis of T. implicatus occurs within sperm cysts, following a pattern commonly found in insects. The microtubular doublets of spermatid axoneme exhibit a hooklike projection from the B-subtubule in the early period, but the projection disappears in the mature stage. The mature spermatozoon of T. implicatus is a filiform cell that is pronouncedly elongated and has a bi-layered acrosome, a nucleus with two lateral longitudinal grooves, a neck region with the centriole adjunct, a flagellum with a simple 9 + 2 axoneme, two extra-axonemal accessory structures, two accessory bodies, and two mitochondrial derivatives of unequal size, and a prominent glycocalyx. The basic structure of spermatozoa of T. implicatus is similar to that of other Mecoptera studied. However, this species shows characteristics unique in Bittacidae, such as the reniform appearance of the centriole adjunct, two triangular accessory bodies with granular materials, and two asymmetric mitochondrial derivatives with a circular profile in cross-section. The potential utilization of the sperm ultrastructure for understanding the phylogeny of Bittacidae is briefly discussed.

Ultrastructure of the rectum of the soil-spraying larva in Bittacus cirratus (Mecoptera: Bittacidae) Abstract The larvae of Bittacidae have an interesting behavior of spraying soil particles on their body surface through the anus. However, the hindgut specialization associated with this behavior has rarely been studied hitherto. Here, we investigated the fine structure of the larval rectum in the hangingfly Bittacus cirratus Tjeder using light and transmission electron microscopy. The results show that the larvae of B. cirratus have a tubular rectum without rectal pads or papillae. The rectum consists of well-developed visceral muscle layers, a non-cellular basal lamina, a single-layer epithelium with a cuticular intima, and a central lumen. The folded rectal epithelium consists of two types of flattened epithelial cells: electron-dense type I cells and electron-lucent type II cells. The apical and basal plasma membranes are infolded and are associated with mitochondria in the epithelial cells. The epithelial cells are held by septate and scalariform junctions. The lateral cell membranes are combined with mitochondria among type I cells and generate mitochondria-scalariform junction complexes. These features suggest that the epithelial cells are active in water and ion reabsorption. We conclude that the absence of rectal pads or papillae and the presence of developed circular muscles are likely morphological adaptations of these larvae to the soil-spraying behavior.

Floral micromorphology and nectar composition of the early evolutionary lineage Utricularia (subgenus Polypompholyx , Lentibulariaceae) Abstract Utricularia (Lentibulariaceae) is a genus comprising around 240 species of herbaceous, carnivorous plants. Utricularia is usually viewed as an insect-pollinated genus, with the exception of a few bird-pollinated species. The bladderworts Utricularia multifida and U. tenella are interesting species because they represent an early evolutionary Utricularia branch and have some unusual morphological characters in their traps and calyx. Thus, our aims were to (i) determine whether the nectar sugar concentrations and composition in U. multifida and U. tenella are similar to those of other Utricularia species from the subgenera Polypompholyx and Utricularia, (ii) compare the nectary structure of U. multifida and U. tenella with those of other Utricularia species, and (iii) determine whether U. multifida and U. tenella use some of their floral trichomes as an alternative food reward for pollinators. We used light microscopy, histochemistry, and scanning and transmission electron microscopy to address those aims. The concentration and composition of nectar sugars were analysed using high-performance liquid chromatography. In all of the examined species, the floral nectary consisted of a spur bearing glandular trichomes. The spur produced and stored the nectar. We detected hexose-dominated (fructose + glucose) nectar in U. multifida and U. tenella as well as in U. violacea. In both U. multifida and U. tenella, there were trichomes that blocked the entrance into the throat and spur. Because these trichomes were rich in chromoplasts and contained lipid droplets, they may form an additional visual attractant. Bearing in mind the phylogenetic hypothesis for the genus, we suggest that an early ancestor of Utricularia had a nectariferous spur flower with a lower lip that formed a wide landing platform for bee pollinators.

Different colored Chrysanthemum × morifolium cultivars represent distinct plastid transformation and carotenoid deposit patterns Abstract Carotenoids are the most important pigments determining the color of C. × morifolium; however, it is still unknown whether the changes of plastid ultrastructure affect carotenoids accumulation. In this study, we compared the change of carotenoid composition, content, and the plastid ultrastructures in the different developmental stages of capitulum among fourteen C. × morifolium cultivars from seven color groups. We found that the carotenoids and plastids detected at the early stage of capitulum development were similar in all cultivars, including violaxanthin, lutein, and β-carotene, which were present in proplastids and immature chloroplasts. Immature chloroplasts were degraded completely, forming loosely broken plastids during the development of the capitulum in white and pink cultivars. Meanwhile, a number of lipid vesicles appeared at proplastids, which resulted in only trace amounts of carotenoid accumulation in these cultivars. For yellow, orange, red, and brown cultivars, a great number of chromoplasts were found, which contained diverse ultrastructures, such as plastoglobules, tubules, and lipid droplets; these chromoplasts were derived from proplastids or chloroplasts. Compared with the early stage of capitulum development, these cultivars accumulated large amounts of carotenoids, primarily including lutein, lutein derivatives, and their isomers. In green cultivars, proplastids and immature chloroplasts were completely transformed into mature chloroplasts. These chloroplasts mainly contained violaxanthin, lutein, β-carotene, and two new components, (9Z)-lutein and (9’Z)-lutein, compared with carotenoid components presented in proplastids and immature chloroplasts. This research will be helpful for understanding the mechanisms of carotenoid metabolism of C. × morifolium. Furthermore, we found that two different chromoplast transformation patterns could be present in the same tissue cell, which contributed to the research on plastid differentiation and development in higher plants.