Recent investigations show that exogenously applied small interfering RNAs (siRNA) and long double-stranded RNA (dsRNA) precursors can be taken up and translocated in plants to induce RNA interference (RNAi) in the plant or in its fungal pathogen. The question of whether genes in the plant genome can undergo suppression as a result of exogenous RNA application on plant surface is almost unexplored. This study analyzed whether it is possible to influence transcript levels of transgenes, as more prone sequences to silencing, in Arabidopsis genome by direct exogenous application of target long dsRNAs. The data revealed that in vitro synthesized dsRNAs designed to target the gene coding regions of enhanced green fluorescent protein (EGFP) or neomycin phosphotransferase II (NPTII) suppressed their transcript levels in Arabidopsis. The fact that, simple exogenous application of polynucleotides can affect mRNA levels of plant transgenes, opens new opportunities for the development of new scientific techniques and crop improvement strategies.

In bivalves neurotransmitters are involved in a variety of behaviors, but their diversity and distribution in the nervous system of these organisms remains somewhat unclear. Here, we first examined immunohistochemically the distributions of neurons containing different neurotransmitters, neuropeptides, and related enzymes, as well as the proliferative status of neurons in the ganglia of the mussel Crenomytilus grayanus. H-Phe-Met-Arg-Phe-NH2 (FMRFamide), choline acetyltransferase (ChAT), γaminobutyric acid (GABA) and tyrosine hydroxylase (TH) were found to be expressed by neurons in all the ganglia, whereas serotonin (5-HT) neurons were found only in the cerebropleural and pedal, but not visceral ganglia. Moreover, incubation of living mussels in the presence of a 5-HT precursor (5-HTP) confirmed the absence of 5-HT-containing neurons from the visceral ganglia, indicating that the "serotonin center" of the visceral nervous system is located in the cerebral ganglia. Furthermore, immunostaining of molecules related to neurotransmission together with α-acetylated tubulin demonstrated that this cytoskeletal protein may be a potential pan-neuronal marker in bivalves. Adult mussel neurons do not proliferate, but a population of proliferating PCNA-LIP cells which do not express any of the neurotransmitters examined, perhaps glia cells, was detected in the ganglia. These novel findings suggest that the nervous system of bivalves contains a broad variety of signal molecules most likely involved in the regulation of different physiological and behavioral processes. In addition, proliferating cells may maintain and renew glial cells and neurons throughout the lives of bivalves.

Exogenous application of double-stranded RNAs (dsRNAs) and small-interfering RNAs (siRNAs) to plant surfaces has emerged as a promising method for regulation of essential genes in plant pathogens and for plant disease protection. Yet, regulation of plant endogenous genes via external RNA treatments has not been sufficiently investigated. In this study, we targeted the genes of chalcone synthase (CHS), the key enzyme in the flavonoid/anthocyanin biosynthesis pathway, and two transcriptional factors, MYBL2 and ANAC032, negatively regulating anthocyanin biosynthesis in Arabidopsis. Direct foliar application of AtCHS-specific dsRNAs and siRNAs resulted in an efficient downregulation of the AtCHS gene and suppressed anthocyanin accumulation in A. thaliana under anthocyanin biosynthesis-modulating conditions. Targeting the AtMYBL2 and AtANAC032 genes by foliar dsRNA treatments markedly reduced their mRNA levels and led to a pronounced upregulation of the AtCHS gene. The content of anthocyanins was increased after treatment with AtMYBL2-dsRNA. Laser scanning microscopy showed a passage of Cy3-labeled AtCHS-dsRNA into the A. thaliana leaf vessels, leaf parenchyma cells, and stomata, indicating the dsRNA uptake and spreading into leaf tissues and plant individual cells. Together, these data show that exogenous dsRNAs were capable of downregulating Arabidopsis genes and induced relevant biochemical changes, which may have applications in plant biotechnology and gene functional studies.

The biplexiform cell (bpxRGC) is a relatively and recently discovered type of retinal ganglion cells. Like "ordinary" ganglion cells, bpxRGCs have dendrites arborizing within the inner plexiform layer. However, as distinct from other ganglion cells, they have dendrites ascending to the outer plexiform layer. To date, bpxRGCs have been found in mammals, amphibians, and teleost fishes (Cook et al. [1996] Vis Neurosci 13:517-528). The mammalian and amphibian bpxRGCs form direct contacts with photoreceptors and may participate in rapid signal transmission to the brain (Mariani [1982] Science 216:1134-1136; Straznicky and Gábriel [1995] J Hirnforsch 36:135-141). The synaptic organization of teleost bpxRGCs has not been studied. We have studied the synaptic structure of bpxRGCs in the teleost fish Hexagrammos octogrammus. In the sclerad part of the outer plexiform layer, bpxRGC dendrites occurred among the elements in invaginated ribbon synapses (triads) in cone pedicles and rod spherules. Earlier, we showed that greenling bpxRGCs project to the optic tectum (Podugolnikova et al. [2002] Sensornye systemy 15:44-53). We suggest that greenling bpxRGCs participate in some of the tectum-mediated reactions requiring a quick launch of visuomotor reflexes.

Pollen ultrastructure has been studied in two relict and rare species of the genus Aristolochia, A. contorta Bunge and A. manshuriensis Kom. (Aristolochiaceae). Both species have inaperturate, spheroidal, sometimes distally monocolpate or distally bicolpate pollen grains. The equatorial and polar axes of pollen grain in A. manshuriensis are 48.5 and 44.0 μm, respectively. The percentage of defective pollen grains in A. manshuriensis is 3.4%. The fossulate, perforated exine is up to 2.3 μm in thickness; the sexine and the nexine are almost equal in thickness. In A. contorta, the equatorial axis of pollen grain is 36.6 μm: the defectiveness percentage, 24.5%. The exine is verrucate, up to 0.3 μm in thickness, while the sexine is two to three times thicker than the nexine. The pollen germination experiments have shown that pollen of A. manshuriensis, in contrast to A. contorta, can germinate in 10-20% sucrose at 22°С. These data and the high percentage of pollen defectiveness in A. contorta indicate that the androecium function in this species is reduced. The reduction of the androecium function is evidenced by a small amount of pollen grains in anthers or empty anthers and a high percentage of defective pollen grains.

Experimental studies showed that in echinoids egg size of a species affects magnitude of phenotypic plasticity in larvae of the species. Here we tested whether any difference in magnitude of plasticity exists in pre-feeding larvae of two sea urchins, Mesocentrotus nudus (A. Agassiz, 1864) and Strongylocentrotus intermedius (A. Agassiz, 1864). These species are closely related by their phylogenetic position, have overlapping ranges, and differ by size of their eggs. Our results indicate that by the end of pre-feeding development (4 d after fertilization) the larvae from high algae treatment (8 000 cells 1 ml-1) had shorter post-oral arms as compared to their siblings of the same age from no algae treatment (0 cells 1 ml-1). In spite the egg volume of M. nudus was approximately 2-times bigger than that in S. intermedius, relative difference in post-oral arms length in no algae and high algae conditions in S. intermedius was approximately 1.5 times larger. Our results support the assumption that the degree of phenotypic plasticity in the larvae, developing from smaller eggs with lower maternal investment, is higher than in the larvae, developing from bigger eggs. We propose that pre-feeding larvae of S. intermedius are more phenotypically plastic than the larvae of M. nudus.

Larvae of many echinoids are known to be phenotypically plastic and capable of changing the growth rate of their post-oral arms depending on the microalgae concentration in their habitat. As literature data show, developing larvae use chemosensation to detect algae in the environment and "adjust" the rate of growth of their post-oral arms through dopamine signaling. According to our results, dopamine has a significant effect on the post-oral arm growth in early larvae of two sea urchin species, Mesocentrotus nudus and Strongylocentrotus intermedius. The dopamine effect depends on concentration: the higher the dopamine concentration in the water, the shorter the post-oral arms. We suggest that the pattern of response to variation in dopamine concentration, manifested by early larvae of both species, is similar to that observed at different concentrations of microalgae.

Two types of cells were observed in germinative epithelium of male and female sea urchins: germ cells and somatic accessory cells; the latter referred to as nutritive phagocytes. At the onset of gametogenesis, nutritive phagocytes accumulate nutrients and greatly increase in their size. As gametogenesis progresses, the accumulated nutrients are transferred from nutritive phagocytes into developing gametes, and size of the nutritive phagocytes decreases. An electron microscopic study of nutritive phagocytes in sea urchins, Strongylocentrotus intermedius, at different stages of annual reproductive cycle showed for the first time that both macro- and microautophagy take place in nutritive phagocytes. Both processes occur simultaneously and regulate size and composition of nutritive phagocytes in male and female sea urchins. Nutritive phagocytes consume redundant cytoplasm via macroautophagy. Microautophagy is probably involved in consumption of redundant membranes that appear within nutritive phagocytes due to destruction of nutrient-storing globules, macroautophagy, and phagocytosis of germ cells or their remnants.