Sequences of cDNAs and expression of genes encoding chitin synthase and chitinase in the midgut of Spodoptera frugiperda.
The focus of this study was on the characterization and expression of genes encoding enzymes responsible for the synthesis and degradation of chitin, chitin synthase (SfCHSB) and chitinase (SfCHI), respectively, in the midgut of the fall armyworm, Spodoptera frugiperda. Sequences of cDNAs for SfCHSB and SfCHI were determined by amplification of overlapping PCR fragments and the expression patterns of these two genes were analyzed during insect development by RT-PCR. SfCHSB encodes a protein of 1523 amino acids containing several transmembrane segments, whereas SfCHI encodes a protein of 555 amino acids composed of a catalytic domain, a linker region and a chitin-binding domain. SfCHSB is expressed in the midgut during the feeding stages, whereas SfCHI is expressed during the wandering and pupal stages. Both genes are expressed along the whole midgut. Chitin staining revealed that this polysaccharide is present in the peritrophic membrane (PM) only when SfCHSB is expressed. There is little or no chitin in the midgut when SfCHI is expressed. These results support the hypothesis that SfCHSB is responsible for PM chitin synthesis during the larval feeding stages and SfCHI carries out PM chitin degradation during larval-pupal molting, suggesting mutually exclusive temporal patterns of expression of these genes.
Bolognesi
Renata
R
USDA-ARS-Grain Marketing and Production Research Center, Manhattan, KS 66502, USA.
Arakane
Yasuyuki
Y
Muthukrishnan
Subbaratnam
S
Kramer
Karl J
KJ
Terra
Walter R
WR
Ferreira
Clélia
C
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002687:Chitin Synthase / Q000235:genetics*; D002688:Chitinases / Q000235:genetics*; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics*; D018507:Gene Expression Regulation, Developmental; D015971:Gene Expression Regulation, Enzymologic; D017344:Genes, Insect; D008969:Molecular Sequence Data; D020133:Reverse Transcriptase Polymerase Chain Reaction; D018411:Spodoptera / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development
D018076:DNA, Complementary; D002687:Chitin Synthase; D002688:Chitinases