An insight on Drosophila myogenesis and its assessment techniques.

Movement assisted by muscles forms the basis of various behavioural traits seen in Drosophila. Myogenesis involves developmental processes like cellular specification, differentiation, migration, fusion, adherence to tendons and neuronal innervation in a series of coordinated event well defined in body space and time. Gene regulatory networks are switched on-off, fine tuning at the right developmental stage to assist each cellular event. Drosophila is a holometabolous organism that undergoes myogenesis waves at two developmental stages, and is ideal for comparative analysis of the role of genes and genetic pathways conserved across phyla. In this review we have summarized myogenic events from the embryo to adult focussing on the somatic muscle development during the early embryonic stage and then on indirect flight muscles (IFM) formation required for adult life, emphasizing on recent trends of analysing muscle mutants and advances in Drosophila muscle biology.

Chronic lead (Pb) exposure results in diminished hemocyte count and increased susceptibility to bacterial infection in Drosophila melanogaster.

Heavy metal Pb is a common toxic pollutant present in our environment adversely affecting health of the living organisms. Recent studies suggest positive correlation between heavy metal exposure and immune dysfunction and present work utilizes Drosophila to address this issue in relation to Pb exposure. In-vivo Pb toxicity was established by dietary intake where essential parameters like development and life span were found to be hampered and augmented upon metallothionein B (mtnB) downregulation hinting towards potential role of mtnB in Pb detoxification. Further response of Drosophila to B. subtilis bacterial infection was monitored by carrying out oral infections. Pb fed flies showed increased susceptibility to infection as compared to their controls. Since Drosophila hemocytes play dual role as immune cells, we checked for the total hemocyte count and found significant decrease in hemocyte numbers in Pb fed larvae. Both crystal cells and plasmatocytes, the two major hemocytes in third instar larval hemolymph were reduced. However we did not find any visible morphological changes in Giemsa stained hemocytes. Crystal cells are crucial for synthesis and release of phenoloxidase (PO), an enzyme required for melanin clot synthesis and deposition. PO activity assessed from total hemolymph protein isolates was found to be substantially decreased in Pb raised animals. Results were also confirmed by spot test and native gel activity assay of PO. Overall our results suggest immunotoxic effect of Pb through decrease in hemocyte count including crystal cell which in turn leads to decreased PO activity and increased susceptibility to B. subtilis.