Inhibition of agrobacterial oncogenes expression by means of antisense RNA

Plant's infection with soil bacteria Agrobacterium tumefaciens lead to tumour formation, so called crown galls. The reason of tumorigenesis is integration of agrobacterial genes for phytohormone synthesis auxins and cytokinins in plant genome, the most important of them are iaaM and ipt. Obtaining of transgenic plants able to inhibit these genes expression, creates conditions for producing of plants resistant to crown gall disease. With this purpose single and double transformants of tobacco plants with antisense copies of iaaM and ipt genes under the control of single and double promoters of 35S RNA of cauliflower mosaic virus (CaMV 35S and CaMV 35SS) were produced. Infection with virulentA. tumefaciens strains C58 (pTiC58) and A6 (pTiA6) of all types transgenic plants with antisense oncogenes copies showed essential but incomplete inhibition of these genes expression. After agrobacterial transformations of transgenic plants only "weakened" tumours of various morphology, able to regenerate the whole plants, were formed. The analysis data of inhibition of iaaM and ipt genes expression in formed tumour cells were presented. The results indicate perspective RNA-interference strategy for producing of plants resistant to agrobacterial crown gall disease.     

Cuticle hydrolysis in four medically important fly species by enzymes of the entomopathogenic fungus Conidiobolus coronatus

Entomopathogenic fungi infect insects via penetration through the cuticle, which varies remarkably in chemical composition across species and life stages. Fungal infection involves the production of enzymes that hydrolyse cuticular proteins, chitin and lipids. Host specificity is associated with fungus–cuticle interactions related to substrate utilization and resistance to host‐specific inhibitors. The soil fungus Conidiobolus coronatus (Constantin) (Entomophthorales: Ancylistaceae) shows virulence against susceptible species. The larvae and pupae of Calliphora vicina (Robineau‐Desvoidy) (Diptera: Calliphoridae), Calliphora vomitoria (Linnaeus), Lucilia sericata (Meigen) (Diptera: Calliphoridae) and Musca domestica (Linnaeus) (Diptera: Muscidae) are resistant, but adults exposed to C. coronatus quickly perish. Fungus was cultivated for 3 weeks in a minimal medium. Cell‐free filtrate, for which activity of elastase, N‐acetylglucosaminidase, chitobiosidase and lipase was determined, was used for in vitro hydrolysis of the cuticle from larvae, puparia and adults. Amounts of amino acids, N‐glucosamine and fatty acids released were measured after 8 h of incubation. The effectiveness of fungal enzymes was correlated with concentrations of compounds detected in the cuticles of tested insects. Positive correlations suggest compounds used by the fungus as nutrients, whereas negative correlations may indicate compounds responsible for insect resistance. Adult deaths result from the ingestion of conidia or fungal excretions.     

Individual optimization: Mechanisms shaping the optimal reaction norm

In general, optimal reaction norms in heterogeneous populations can be obtained only by iterative numerical procedures (McNamara, 1991; Kawecki and Stearns, 1993). We consider two particular, but biologically plausible and analytically tractable cases of individual optimization to gain insight into the mechanisms which shape the optimal reaction norm of fecundity in relation to an environmental variable or an individual trait. In the first case, we assume that the quality of the environment (e.g. food abundance) or the quality of the individual (e.g. body size) is fixed during its entire life; it may also be a heritable individual trait. In the second case, individual quality is assumed to change randomly such that the probability distribution of quality in the next year is the same for the parent and for her offspring. For these two cases, we obtain analytical expressions for the shape of the optimal reaction norm, which are heuristically interpretable in terms of underlying selective mechanisms. It is shown that better quality may reduce the optimal fecundity. This outcome is particularly likely if better quality increases a fecundity-independent factor of parental survival in a long-lived species with fixed quality. This revised version was published online in July 2006 with corrections to the Cover Date.     

Spawning seasons of Rasbora tawarensis (Pisces: Cyprinidae) in Lake Laut Tawar,Aceh Province,Indonesia

Background  

Rasbora tawarensis is an endemic freshwater fish in Lake Laut Tawar, Aceh Province, Indonesia. Unfortunately, its status is regarded as critical endangered with populations decreasing in recent years. To date no information on the spawning activities of the fish are available. Therefore, this study provides a contribution to the knowledge on reproductive biology of R. tawarensis especially on spawning seasons as well as basic information for conservation of the species.