Plugging into the network: belowground connections between germlings and extraradical mycelium of arbuscular mycorrhizal fungi.

Arbuscular mycorrhizal fungi (AMF) are obligate biotrophs; nevertheless their spores can germinate in the absence of host plants. Such inconsistent behavior is balanced by diverse survival strategies. The ability of AM fungal hyphae to fuse might represent a fundamental survival strategy because germlings could plug into compatible mycorrhizal networks, thus gaining access to plant-derived carbon before asymbiotic growth arrest. An in vivo experimental system was used to grow extraradical mycelium produced by Glomus mosseae colonizing three different plant species and germlings of the same isolate. After symbiotic and asymbiotic mycelia came into contact we showed that germling hyphae fused with symbiotic network hyphae and established protoplasm connections with nuclei occurring in fusion bridges. The frequency of anastomoses between germling and symbiotic hyphae was 4.9-23.9%. Prefusion and postfusion incompatible responses, with protoplasm withdrawal in interacting hyphae, were evident in some hyphal contacts. Given the multigenomic nature of AMF, the mingling of germling nuclei with those of the mycorrhizal network through perfect fusions might represent a means for the maintenance of genetic diversity in the absence of sexual recombination.

Life cycle and mating behavior of Zygotylenchus guevarai (Nematoda: Pratylenchidae) on excised Petroselinum crispum roots.

The life cycle and mating behavior of Zygotylenchus guevarai were observed in vitro on excised roots of Petroselinum crispum in gnotobiotic culture. Eggs hatched into juveniles whose appearance and structure were similar to those of the adults. Juveniles grew in size and each juvenile stage was terminated by a molt. Z. guevarai had four juvenile stages with the first molt occurred outside the egg shortly after hatching. After the final molt the juveniles differentiated into adult males and females. Mating was required for reproduction. After mating, fertilized females began to lay eggs. The life cycle from second stage juvenile to second stage juvenile was completed in 43 days.

Effects of Petroselinum crispum extract on pancreatic B cells and blood glucose of streptozotocin-induced diabetic rats.

This study investigated both morphologically and biochemically whether parsley (Petroselinum crispum), which is used as a folk remedy to decrease blood glucose, has any antidiabetic effect on pancreatic B cells of rats. Parsley extract was given to male diabetic rats. In the diabetic group given parsley extract, it was detected that the number of secretory granules and cells in islets and other morphologic changes were not different from the control diabetic group, while the blood glucose levels in the diabetic group given the plant extract were reduced in comparison to the diabetic group. In addition, a decrease was observed in the weight of the control diabetic group and the diabetic group given the plant extract. It is suggested that the plant therapy can provide blood glucose homeostasis and cannot regenerate B cells of the endocrine pancreas.

Non-self recognition, transcriptional reprogramming, and secondary metabolite accumulation during plant/pathogen interactions.

Disease resistance of plants involves two distinct forms of chemical communication with the pathogen: recognition and defense. Both are essential components of a highly complex, multifaceted defense response, which begins with non-self recognition through the perception of pathogen-derived signal molecules and results in the production, inter alia, of antibiotically active compounds (phytoalexins) and cell wall-reinforcing material around the infection site. To elucidate the molecular details and the genomic basis of the underlying chains of events, we used two different experimental systems: suspension-cultured cells of Petroselinum crispum (parsley) and wild-type as well as mutant plants of Arabidopsis thaliana. Particular emphasis was placed on the structural and functional identification of signal and defense molecules, and on the mechanisms of signal perception, intracellular signal transduction and transcriptional reprogramming, including the structural and functional characterization of the responsible cis-acting gene promoter elements and transacting regulatory proteins. Comparing P. crispum and A. thaliana allows us to distinguish species-specific defense mechanisms from more universal responses, and furthermore provides general insights into the nature of the interactions. Despite the complexity of the pathogen defense response, it is experimentally tractable, and knowledge gained so far has opened up a new realm of gene technology-assisted strategies for resistance breeding of crop plants.