Ecdysone signaling is required for proper organization and fluid secretion of stellate cells in the Malpighian tubules of Drosophila melanogaster

Abstract

Drosophila development is a tightly regulated process involving metamorphosis of a relatively less mobile larva to a highly motile adult, triggered by secretion of 20-hydroxyecdysone. Under the influence of ecdysone, most of the larval tissues degenerate, while the imaginal cells differentiate and form adult specific structures. Although the larval Malpighian tubules do not seem to be affected by ecdysone during metamorphosis, we show that ecdysone signaling plays an important role in the early development and functioning of Malpighian tubules. Disruption of ecdysone receptor function, using targeted expression of dominant negative ecdysone receptor in stellate cells, results in disruption of organization of Malpighian tubules. The number of stellate cells is reduced in such Malpighian tubules. Further, they get clustered rather than distributed in their characteristic wild type pattern. We also demonstrate that expression of Drosophila integrin protein (DRIP), an aquaporin responsible for trans-cellular water transport, is also reduced in stellate cells when ecdysone signaling is disrupted. Our results show that of the three ecdysone receptor isoforms, only EcR-B2 rescues these phenotypes. A similar pattern of stellate cell clustering and reduced expression of DRIP is observed in ecd 1 , a temperature sensitive mutant, under non-permissive conditions. These results suggest that ecdysone signaling is required for proper patterning and functioning of stellate cells and that EcR-B2 may be the primary isoform required for ecdysone signaling in stellate cells.

Early gene Broad complex plays a key role in regulating the immune response triggered by ecdysone in the Malpighian tubules of Drosophila melanogaster

“…Interestingly, we have identified EcR isoforms B1 and B2 to be involved in MTs immune response as shown earlier in S2-cell line where enhanced expression of Relish is observed after transfecting cells with EcR-B1 and B2 (Celine, 2010). The importance of EcR-B1 and EcR-B2 in the development and function of MTs has been reported earlier (Gautam and Tapadia, 2010) and the present results strengthens the conclusion that EcRB1 and B2 are the predominant isoforms required for the functioning of MTs.…”

“…The immune response in MTs is developmentally regulated and they show constitutive immune response independent of infection (Verma and Tapadia, 2012). Ecdysone has an important role in the development of MTs (Gautam and Tapadia, 2010), but during metamorphosis it does not lead to their histolysis as other larval tissues (Shukla and Tapadia, 2011).…”

Non-apoptotic function of apoptotic proteins in the development of Malpighian tubules of Drosophila melanogaster

“…Recent studies have shown that the PCs and SCs of MTs originate from two different lineages, with PCs originating from ectodermal epithelial buds in the hindgut and the SCs from the caudal mesoderm cells that lie above the hindgut in the region from where MTs bud (Denholm et al 2003). Ecdysone regulates the proper intercalation and integration of these cell types as well as fluid secretion (Gautam and Tapadia 2010). During metamorphosis, extensive remodelling of the entire organism takes place wherein most of the larval tissues undergo apoptosis and adultspecific structures are made.…”

Ecdysone Elicits Chronic Renal Impairment via Mineralocorticoid-Like Pathogenic Activities

“…In stark contrast to the traditional opinion that natural medications used by alternative medical practices are largely safe and beneficial by exerting a normalizing effect upon bodily processes, a growing body of evidence recently suggests that a number of natural medications might be detrimental to kidney health [6,[9][10][11]. In particular, ecdysone targets the drosophila Malpighian tubules, which are equivalent to renal tubules in mammals, and regulates ionic changes and water retention in arthropods [12,13]. Recently, the use of ecdysone-containing adaptogens in mammalian has been associated with kidney growth and enlargement [14][15][16], which are evident clinical signs of disturbed kidney homeostasis.…”