Characterization and expression patterns of a membrane-bound trehalase from Spodoptera exigua.
BACKGROUND
The chitin biosynthesis pathway starts with trehalose in insects and the main functions of trehalases are hydrolysis of trehalose to glucose. Although insects possess two types, soluble trehalase (Tre-1) and membrane-bound trehalase (Tre-2), very little is known about Tre-2 and the difference in function between Tre-1 and Tre-2.


RESULTS
To gain an insight into trehalase functions in insects, we investigated a putative membrane-bound trehalase from Spodoptera exigua (SeTre-2) cloned from the fat body. The deduced amino acid sequence of SeTre-2 contains 645 residues and has a predicted molecular weight of approximately 74 kDa and pI of 6.01. Alignment of SeTre-2 with other insect trehalases showed that it contains two trehalase signature motifs and a putative transmembrane domain, which is an important characteristic of Tre-2. Comparison of the genomic DNA and cDNA sequences demonstrated that SeTre-2 comprises 13 exons and 12 introns. Southern blot analysis revealed that S. exigua has two trehalase genes and that SeTre-2 is a single-copy gene. Northern blot analyses showed that the SeTre-2 transcript is expressed not only in the midgut, as previously reported for Bombyx mori, but also in the fat body and Malpighian tubules, although expression patterns differed between the midgut and fat body. SeTre-2 transcripts were detected in the midgut of feeding stage larvae, but not in pupae, whereas SeTre-2 mRNA was detected in the fat body of fifth instar larvae and pupae.


CONCLUSIONS
These findings provide new data on the tissue distribution, expression patterns and potential function of membrane-bound trehalase. The results suggest that the SeTre-2 gene may have different functions in the midgut and fat body.
Tang
Bin
B
State Key Laboratory of Biocontrol and Institute of Entomology, School of Life Sciences, Sun Yat-sen University, Guangzhou, PR China. tbzm611@yahoo.com
Chen
Xiaofei
X
Liu
Yang
Y
Tian
Honggang
H
Liu
Jian
J
Hu
Jian
J
Xu
Weihua
W
Zhang
Wenqing
W
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D015139:Blotting, Southern; D005091:Exons / Q000235:genetics; D005216:Fat Body / Q000378:metabolism; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D015971:Gene Expression Regulation, Enzymologic; D019476:Insect Proteins / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D007438:Introns / Q000235:genetics; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D010802:Phylogeny; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D018411:Spodoptera / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D014198:Trehalase / Q000145:classification / Q000235:genetics / Q000378:metabolism*
D019476:Insect Proteins; D008565:Membrane Proteins; D012333:RNA, Messenger; D014198:Trehalase