Expression of multidrug resistance proteins is localized principally to the Malpighian tubules in larvae of the cabbage looper moth, Trichoplusia ni

Abstract

SUMMARYThe multidrug resistance proteins (MRPs) serve a number of important roles in development, physiological homeostasis and metabolic resistance. In insects, they may also contribute to resistance against xenobiotics including insecticides and plant secondary metabolites. To investigate their contribution to xenobiotic resistance, we have examined the tissue distribution of gene and protein expression of the multidrug resistance proteins TrnMRP1 and TrnMRP4 of the lepidopteran insect, Trichoplusia ni. Using quantitative PCR and immunohistochemistry, we have identified high expression levels of both transporters in the Malpighian tubules relative to levels in other major tissues of the body, where they probably contribute to excretion of metabolic wastes or ingested xenobiotics. We have specifically located TrnMRP protein expression in a subpopulation of Malpighian tubule secondary cells. Expression of TrnMRP1 was also detected both at a high level in specific cortical neurons of larval ganglia and at a lower level throughout the cortex, where it may act in signaling or protective functions, respectively. In contrast, expression of TrnMRP4 was low to absent in larval ganglia, with the exception of single cells in the central connective. We discuss the potential implications of this TrnMRP activity on insect development and metabolic resistance.

Multidrug resistance protein gene expression inTrichoplusia nicaterpillars

“…Labbé et al . () examined two genes encoding members of another ABC protein subfamily known to confer drug resistance, the multidrug resistance proteins (MRPs), in T. ni . TrnMRP1 and trnMRP4 mRNAs were both detected in the Malpighian tubules, and trnMRP4 mRNA was also found in the gut.…”

“…It is interesting that even though the protein products of both mdr49 (Wu et al, 1991) and mdr65 (Begun & Whitely, 2000;Mayer et al, 2009) are associated with xenobiotic resistance, only an induction of mdr49 expression was observed. Labbé et al (2011b) examined two genes encoding members of another ABC protein subfamily known to confer drug resistance, the multidrug resistance proteins (MRPs), in T. ni. TrnMRP1 and trnMRP4 mRNAs were both detected in the Malpighian tubules, and trnMRP4 mRNA was also found in the gut.…”

“…The qPCR protocol consisted of a 10 min, 95°C activation step followed by 35 cycles of a 10 s, 95°C melting step, a 30 s, 60°C annealing step and a 15 s, 72°C extension step, and fluorescence was measured after the extension step of each cycle. Gene-specific qPCR primer pairs and hydrolysis probes were designed for two reference genes, eukaryotic Initiation Factor-4a (eIF4a) and ribosomal protein S5 (Labbé et al, 2011b), as well as trnMDR1, trnMDR2 and trnMDR3 (Table 1). Each primer pair was tested by PCR amplifying T. ni cDNA and no template controls composed of sterile water.…”

Overexpression of a cytochrome P450 and a UDP-glycosyltransferase is associated with imidacloprid resistance in the Colorado potato beetle, Leptinotarsa decemlineata

“…These tissues were selected because expression of detoxifying enzymes and ABC transporters are often enriched in these tissues 19, 30, 56, 57 . The three tissues were pooled and total RNA was isolated using an RNeasy Plant Mini Kit (Qiagen).…”

Malpighian tubules ofTrichoplusia ni: recycling ions via gap junctions and switching between secretion and reabsorption of Na+ and K+ in the distal ileac plexus

“…Stellate cells of dipterans (a SC equivalent) were in the past believed to lack primary active transport mechanisms on the basis of their simple cytoarchitecture and lack of cellular structures characteristic of ion-transporting cells (reviewed by Dow, 2012). However, SCs have subsequently been shown to possess many transporters absent from the neighbouring PCs related to ion, water and xenobiotic transport and their endocrine control: inward rectifier K + channel (Kir), multidrug resistance proteins (MRPs), chloride-bicarbonate exchangers (CBE), Na + /K + -ATPase (NKA), Na + /H + exchanger 2 (NHE2), Na + /H + antiporter 2 (NHA2) and leucokinin receptor (LK-R) (Piermarini et al, 2010Labbe et al, 2011;Kersch and Pietrantonio, 2011;Patrick et al, 2006;Day et al, 2008;Xiang et al, 2012). Therefore, a functional designation of the PCs as ion providers in the SC-containing region is not unreasonable.…”