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Cell proliferation, growth and survival are three different basic processes which converge at determining a fundamental property -the size of an organism. Scalloped (Sd) is the first characterised transcriptional partner to Yorkie (Yki), the downstream effector of the Hippo pathway which is a highly potential and evolutionarily conserved regulator of organ size. Here we have studied the hypomorphic effect of sd on the development of Mushroom Bodies (MBs) in Drosophila brain. We show that, sd non-function results in an increase in the size of MBs. We demonstrate that, sd regulation on MB size operates through multiple routes. Sd expressed in the differentiated MB neurons, imposes non-cell autonomous repression on the proliferation of MB precursor cells, and Sd expression in the MB neuroblasts (NB) cell autonomously represses mushroom body neuroblast (MBNB) proliferation. Further Sd in Kenyon cells (KCs) imparts a cell autonomous restriction on their growth. Our findings are distinctive because, while the classical sd loss of function phenotypes in eye, wing and lymph gland are reported as loss of tissue or reduced organ size, the present study shows that, Sd inactivation in the developing MB, promotes precursor cell proliferation and results in an increase in the organ size.

The tumor-suppressor morphogen, Patched (Ptc), has extensive homology to the Niemann-Pick-C 1 (NPC1) protein. The NPC disease is a paediatric, progressive and fatal neurodegenerative disorder thought to be due to an abnormal accumulation of cholesterol in neurons. Here, we report that patched mutant adults develop a progressive neurodegenerative disease and their brain contains membranous and lamellar inclusions. There is also a significant reduction in the number of synaptic terminals in the brain of the mutant adults. Interestingly, feeding cholesterol to wild type flies generates inclusions in the brain, but does not cause the disease. However, feeding cholesterol to mutant flies increases synaptic connections and suppresses the disease. Our results suggest that sequestration of cholesterol in the mutant brain in the form of membranous material and inclusions affects available pool of cholesterol for cellular functions. This, in turn, negatively affects the synaptic number and contributes to the disease-state. Consistent with this, in ptc mutants there is a reduction in the pool of cholesterol esters, and cholesterol-mediated suppression of the disease accompanies an increase in cholesterol esters. We further show that Ptc does not function directly in this process since gain-of-function for Hedgehog also induces the same disease with a reduction in the level of cholesterol esters. We believe that loss of function for ptc causes neurodegeneration via two distinct ways: de-repression of genes that interfere with lipid trafficking, and de-repression of genes outside of the lipid trafficking; the functions of both classes of genes ultimately converge on synaptic connections.

Seven species of the montium subgroup of Drosophila found in South India were analysed with polyacrylamide disc electrophoresis. Eleven loci coding for enzymes were surveyed. The genetic distances between species have been measured. The dendrogram revealed three clusters. The first cluster includes D. nagarholensis, D. agumbensis, D. jambulina and D. kikkawai; the second group consists of D. truncata and D. anomelani; while D. mysorensis was the only species of the third group.

The metaphase karyotypes of eight species of the montium species subgroup of Drosophila are described, of which the information pertaining to six species is new to the literature. Each of these species studied was distinctly different from the others with respect to the metaphase chromosomes, this remarkable degree of differentiation being mainly due to the extensive variability of the 4th and of the Y chromosomes.

Three paracentric inversions constitute the polymorphic system in Drosophila sulfurigaster neonasuta. Of these, two linked inversions, namely 2LA and 2RA, exhibit linkage disequilibrium, and the overall pattern of polymorphism is flexible.