Abstract
Four glycine-rich protein (GRP) genes were identified from expressed sequence tags of the maxillary galea of the silkworm. All four genes were expressed in the maxillary pulp, antenna, labrum, and labium, but none of the genes were expressed in most internal organs. Expression of one of the genes, termed bmSIGRP, was further increased approximately fivefold in the mouth region (including the maxilla, antenna, labrum, labium, and mandible) after 24 h of starvation. bmSIGRP expression peaked at 24 h and gradually declined during the subsequent 2 days. When a synthetic diet not containing proteins was fed, bmSIGRP expression increased significantly in the mouth region to levels similar to that observed in starved larvae. Synthetic diets that lacked vitamins or salts but contained amino acids did not significantly affect bmSIGRP expression. These results suggest that amino acid depletion increases bmSIGRP expression.Electronic supplementary materialThe online version of this article (doi:10.1007/s00360-014-0846-8) contains supplementary material, which is available to authorized users.
Highlights
Glycine-rich proteins (GRPs) with quasi-repetitive glycinerich (GR) motifs (Glyn-X1-2) have been widely identified in prokaryotes and eukaryotes
We identified four GRP genes from expressed sequence tags (ESTs) of maxillary galea from silkworm, and found that one is strongly induced by starvation and amino acid depletion
A few beetle cuticular GRP genes that are induced by an insecticide are thought to provide strength to the beetle’s cuticle and help it survive under severe environmental conditions (Zhang et al 2008)
Summary
Glycine-rich proteins (GRPs) with quasi-repetitive glycinerich (GR) motifs (Glyn-X1-2) have been widely identified in prokaryotes and eukaryotes. These GRPs share similar GR motifs, but their characteristics and functions are diverse. GRPs have been found to act as structural proteins, antimicrobial proteins (Baba et al 1987; Axén et al 1997; Park et al 2000), RNA-binding proteins (Cobianchi et al 1994; Sato 1994), or stress-inducible proteins. Stress-inducible GRPs are extensively documented in plants. Plant GRPs encompass five classes based on their primary structures (Mousavi and Hotta 2005; Mangeon et al 2010). Each class contains several GRPs that are transcriptionally regulated by different types of stresses
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