No abstract

Chitosan, a partially deacetylated form of the natural and biodegradable biopolymer chitin, has been used as plant growth promoter in agriculture. The aim of this work was to investigate the growth promoting responses induced by chitosan at the physiological and molecular level in rice (Oryza sativa L.) seedlings. The combination of the degree of deacetylation (DD), molecular weight and concentration of chitosan had differing effects on the rice seedling growth. For the best enhancement, oligomeric chitosan with an 80 % DD applied at 40 mg/L significantly enhanced the vegetative growth, in terms of the leaf and root fresh weights and dry weights of rice seedlings compared to the control. At the proteomics level, of the 352 rice leaf proteins that could be resolved using the Multi Experiment Viewer software, 105 showed a significantly different expression level in rice leaves treated with chitosan compared to the control. Co-expression network analysis revealed nine of these proteins had significant coexpression with other genes from the three main biochemical network systems of photosynthesis, carbohydrate metabolism and cell redox homeostasis. More than 90 % of the genes positively co-expressed with these nine chitosanresponsive proteins were localized in chloroplasts, suggesting that chitosan enhanced the plant growth of rice seedlings via multiple and complex networks between the nucleus and chloroplast.

No abstract

Nosema ceranae is a microsporidian that infects Apis species. Recently, natural compounds have been proposed to control nosemosis and reduce its transmission among honey bees. We investigated how ethanolic extract of Tetrigona apicalis’s propolis and chito-oligosaccharide (COS) impact the health of N. ceranae-infected Apis dorsata workers. Nosema ceranae spores were extracted from the guts of A. florea workers and fed 106 spores dissolved in 2 µL 50% (w/v) sucrose solution to A. dorsata individually. These bees were then fed a treatment consisting either of 0% or 50% propolis extracts or 0 ppm to 0.5 ppm COS. We found that propolis and COS significantly increased the number of surviving bees and lowered the infection ratio and spore loads of N. ceranae-infected bees 14 days post-infection. Our results suggest that propolis extract and COS could be possible alternative treatments to reduce N. ceranae infection in A. dorsata. Moreover, N. ceranae isolated from A. florea can damage the ventricular cells of A. dorsata, thereby lowering its survival. Our findings highlight the importance of considering N. ceranae infections and using alternative treatments at the community level where other honey bee species can act as a reservoir and readily transmit the pathogen among the honey bee species.