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Labellum structure of Bulbophyllum echinolabium J.J. Sm. (section Lepidorhiza Schltr., Bulbophyllinae Schltr., Orchidaceae Juss.) Abstract This micromorphological, chemical and ultrastructural study is a continuation of research conducted on the section Lepidorhiza. The Bulbophyllum echinolabium flowers comprised features that characterize a sapromyophilous syndrome, having large, glistening parts that emit an intense scent of rotten meat. The secretory activity was described in the hypochile (nectary in longitudinal groove and in the prickles) and the epichile (putative osmophore). The ultrastructural studies revealed a dense cytoplasm in the epidermis and subepidermal tissue with large nuclei and numerous mitochondria, the profiles of SER and RER, and dictyosomes. Large amounts of heterogeneous residues of secreted material (possibly phenolic) were present on the cuticle surface, similar to the unusual prominent periplasmic space with flocculent secretory material. The chemical analysis (GC/MS) of the scent profile of lips comprised carbohydrates and their derivatives (29.55% of all compounds), amino acids (1.66%), lipids (8.04%) and other organic compounds (60.73%). A great number of identified compounds are Diptera attractants (mainly Milichiidae, Tephritidae, Drosophilidae, Muscidae, Sarcophagidae, Tachinidae). The examination of visual and olfactory features indicates correlation between colour of flowers and the type of olfactory mimicry, where a dark colour labellum emits strong smell of rotten waste.

Differentiation of follicular epithelium in polytrophic ovaries of Pieris napi (Lepidoptera: Pieridae)—how far to Drosophila model Abstract Lepidoptera together with its sister group Trichoptera belongs to the superorder Amphiesmenoptera, which is closely related to the Antliophora, comprising Diptera, Siphonaptera, and Mecoptera. In the lepidopteran Pieris napi, a representative of the family Pieridae, the ovaries typical of butterflies are polytrophic and consist of structural ovarian units termed ovarioles. Each ovariole is composed of a terminal filament, germarium, vitellarium, and ovariole stalk. The germarium houses developing germ cell clusters and somatic prefollicular and follicular cells. The significantly elongated vitellarium contains linearly arranged ovarian follicles in successive stages of oogenesis (previtellogenesis, vitellogenesis, and choriogenesis). Each follicle consists of an oocyte and seven nurse cells surrounded by follicular epithelium. During oogenesis, follicular cells diversify into five morphologically and functionally distinct subpopulations: (1) main body follicular cells (mbFC), (2) stretched cells (stFC), (3) posterior terminal cells (pFC), (4) centripetal cells (cpFC), and (5) interfollicular stalk cells (IFS). Centripetal cells are migratorily active and finally form the micropyle. Interfollicular stalk cells derive from mbFC as a result of mbFC intercalation. Differentiation and diversification of follicular cells in Pieris significantly differ from those described in Drosophila in the number of subpopulations and their origin and function during oogenesis.

Bacterial associates of Orthezia urticae , Matsucoccus pini , and Steingelia gorodetskia - scale insects of archaeoccoid families Ortheziidae, Matsucoccidae, and Steingeliidae (Hemiptera, Coccomorpha) Abstract The biological nature, ultrastructure, distribution, and mode of transmission between generations of the microorganisms associated with three species (Orthezia urticae, Matsucoccus pini, Steingelia gorodetskia) of primitive families (archaeococcoids = Orthezioidea) of scale insects were investigated by means of microscopic and molecular methods. In all the specimens of Orthezia urticae and Matsucoccus pini examined, bacteria Wolbachia were identified. In some examined specimens of O. urticae, apart from Wolbachia, bacteria Sodalis were detected. In Steingelia gorodetskia, the bacteria of the genus Sphingomonas were found. In contrast to most plant sap-sucking hemipterans, the bacterial associates of O. urticae, M. pini, and S. gorodetskia are not harbored in specialized bacteriocytes, but are dispersed in the cells of different organs. Ultrastructural observations have shown that bacteria Wolbachia in O. urticae and M. pini, Sodalis in O. urticae, and Sphingomonas in S. gorodetskia are transovarially transmitted from mother to progeny.

Cytological and histochemical evaluations reveal roles of the cotyledonary petiole in the germination and seedling development of Mauritia flexuosa (Arecaceae) Abstract The cotyledonary petiole (CP) completely envelops the embryo axis during embryogenesis in Arecaceae. There is little information available, however, on the roles of that structure in seed germination and initial seedling development—crucial plant life cycle phases. The study therefore sought to evaluate the roles of CP in the germination and post-seminal development of the recalcitrant seeds of Mauritia flexuosa, an ecologically and economically important neotropical palm. The CP and the embryo/vegetative axis were evaluated during germination and initial seedling development using standard morphological, anatomical, histochemical, and ultrastructural methodologies. Evaluations of dormant seeds incubated for 60 days were also performed. The CP (a) promotes seedling protrusion in the germination, extending the embryo axis outside the seed; (b) protects the vegetative axis through the development of coating rich in phenolic compounds and lignin; (c) participates in reserve translocation, with the conversion of its own proteinaceous/mucilaginous reserves into transitional starch, as well as acting in the transport of endospermic reserves; (d) favors aeration, with the formation of pathways among stomata, substomatal chambers, and intercellular spaces; (e) controls seedling morphogenesis by modulating the curvature of the vegetative axis; and (f) contributes to overcoming seed bank dormancy through cytological alterations (protein synthesis and mitochondrial proliferation). The cotyledonary petiole of palms is a unique and multifunctional structure among angiosperms, with crucial roles in germination and seedling establishment.

Impact of antimycin A and myxothiazol on cadmium-induced superoxide, hydrogen peroxide, and nitric oxide generation in barley root tip Abstract In order to gain more insight into the involvement of mitochondrial complex III in the Cd-induced stress, we studied the effect of complex III inhibitors, antimycin A (AA), and myxothiazol (MYXO), on the Cd-induced ROS and NO generation in the barley root tip. Short-term exposure of barley roots to either MYXO or AA provoked a dose-dependent increase in both H2O2 and NO formation. In contrast to H2O2 generation, an enhanced superoxide formation in the transition zone of the root was a characteristic feature of AA-treated roots. MYXO and AA co-treatment had an additive effect on the amount of both H2O2 and NO formed in roots. On the other hand, AA-induced superoxide formation was markedly reversed in roots co-treated with MYXO. Both AA and MYXO exacerbated the Cd-mediated H2O2 or NO generation in the root tip. On the contrary, while AA also exacerbated the Cd-induced superoxide generation, MYXO dose-dependently attenuated it. These data provide strong evidence that ROS generation, a very early symptom of Cd toxicity in roots, is originated in mitochondria. Cd, similarly to AA, generates superoxide by blocking the mitochondrial electron transport chain (ETC) at complex III. In turn, the site of Cd-induced NO generation is not associated with complex III, but ROS formed in mitochondria at this third complex of ETC are probably responsible for enhanced NO generation in barley root under Cd stress.

Atemoya fruit development and cytological aspects of GA 3 -induced growth and parthenocarpy Abstract The exogenous application of GA3 to atemoya tree flowers induces parthenocarpy, and in association with artificial pollination, it increases the fruit size. Morphological, anatomical, ultrastructural, and chemical aspects were evaluated during development of (1) fruit produced by artificial pollination (AP), (2) fruit from AP followed by the application of 250 ppm GA3, and (3) parthenocarpic fruit induced by the application of 1000 ppm GA3. Fruit growth showed a sigmoidal pattern, with development occurring in three phases: (I) cell division, (II) cell differentiation, and (III) maturation. Phase I presented cells with large nuclear volumes and a large population of organelles, phase II presented cells with a reduction in cytoplasm and an increase in vacuole volume, and phase III presented cells with an increase in plastids with reserve compounds. The application of GA3, in association with pollination, precedes cytological events and delays when applied exclusively. GA3 promotes the growth of pollinated fruits by stimulating cell division and expansion, which occur in association with reduced seed production, and the GA3 induces parthenocarpy by maintaining division and stimulating cell expansion. The absence of seeds accounts for the smaller size of the parthenocarpic fruits, and the lower accumulation of calcium accounts for less firm fruit.

Transcriptomic analysis of Chinese wild Vitis pseudoreticulata in response to Plasmopara viticola Abstract Downy mildew, resulted from Plasmopara viticola, is one of most severe fungal diseases of grapevine. Since Vitis vinifera is susceptible to downy mildew, much effort has been focused on improving the resistance of V. vinifera. The Chinese wild V. pseudoreticulata accession Baihe-35-1 (BH) shows resistance to P. viticola; however, the molecular mechanism underlying its resistance to P. viticola is largely unknown. In order to better understand the cellular processes, the transcriptomic changes were investigated at 0, 12, 24, 48, 96, and 120 h post infection (hpi). Transcriptome analysis identified a total of 175 differentially expressed genes. Most of them were found to be associated with oxidative stress, cell wall modification, and protein modification. Moreover, the BH resistance to P. viticola was involved in metabolism process, including terpene synthesis and hormone synthesis. In addition, we verified 12 genes to ensure the accuracy of transcriptome data using quantitative real-time PCR (qRT-PCR). This study broadly characterizes a molecular mechanism in which oxidative stress and cell wall biosynthesis and modification play important roles in the response of BH to P. viticola and provides a basis for further analysis of key genes involved in the resistance to P. viticola.

High temperature and drought stress cause abscisic acid and reactive oxygen species accumulation and suppress seed germination growth in rice Abstract Seed germination is one of the most important biological processes in the life cycle of plants, and temperature and water are the two most critical environmental factors that influence seed germination. In the present study, we investigated the roles of the plant hormone abscisic acid (ABA) and reactive oxygen species (ROS) in high temperature (HT) and drought-induced inhibition of rice seed germination. HT and drought stress caused ABA accumulation in seeds and inhibited seed germination and seedling establishment. Quantitative real-time polymerase chain reaction analysis revealed that HT and drought stress induced the expression of OsNCED3, a key gene in ABA synthesis in rice seeds. In addition, ROS (O2•- and H2O2) and malondialdehyde contents were increased in germinating seeds under HT and drought stress. Moreover, we adopted the non-invasive micro-test technique to detect H2O2 and Ca2+ fluxes at the site of coleoptile emergence. HT and drought stress resulted in a H2O2 efflux, but only drought stress significantly induced Ca2+ influx. Antioxidant enzyme assays revealed that superoxide dismutase (SOD), peroxidase, catalase (CAT), and ascorbate peroxidase (APX) activity were reduced by HT and drought stress, consistent with the expression of OsCu/ZnSOD, OsCATc, and OsAPX2 during seed germination. Altogether, these results suggest that ABA and ROS accumulation under HT and drought conditions can inhibit rice seed germination and growth.

Acute salt stress differentially modulates nitrate reductase expression in contrasting salt responsive rice cultivars Abstract Salt stress response includes alteration in the activity of various important enzymes in plants. Nitrate reductase (NR) is one of the known enzyme affected by salt stress. In this study, contrasting salt responsive cultivars (CVS) (IR64-sensitive and CSR 36-tolerant) were considered to study the regulation of NR genes under salt stress conditions. Using Arabidopsis genes Nia1 and Nia2, three different NR genes were identified in rice and their expression study was conducted. Under stress condition, salt-sensitive CVS (IR64) showed a decrease in NR activity under in vitro and in vivo conditions, whereas tolerant CVS showed an increase in NR activity. Different trends for NR activity in contrasting genotype are explained by the variable number of GATA element in the upstream region of the NR gene. This variation of NR activity in contrasting CVS further co-relates with the transcript level of NR genes. The transcript level of three different NR genes also evidenced the effect of CREs in gene regulation. Promoter (1-kb upstream region) of different NR genes contained different abiotic stress-responsive CREs, which explain the differential behavior of these genes towards the abiotic stress. Overall, this study concludes the role of CREs in the regulation of NR gene and indicates the importance of transcriptional control of NR activity under stress condition. This is the first type of report that highlights the role of the regulatory mechanism of NR genes under salt stress condition.