Coates B S, Hellmich R L, Lewis L C
USDA-ARS, Corn Insects and Crop Genetics Research Unit, Iowa State University, Ames, IA 50010, USA.
Insect Mol Biol. 2006 Feb;15(1):13-24. doi: 10.1111/j.1365-2583.2006.00598.x.
Midgut expressed alkaline serine proteases of Lepidoptera function in conversion of Bacillus thuringiensis (Bt) protoxin to active toxin, and reduced level of transcript T23 is associated with Ostrinia nubilalis resistance to Dipel Bt formulations. Three groups of trypsin- (OnT25, OnT23, and OnT3) and two chymotrypsin-like (OnC1 and OnC2) cDNAs were isolated from O. nubilalis midgut tissue. Intraspecific groupings are based on cDNA similarity and peptide phylogeny. Derived serine proteases showed a catalytic triad (His, Asp, and Ser; except transcript OnT23a), three substrate specificity-determining residues, and three paired disulphide bonds. RT-PCR indicated all transcripts are expressed in the midgut. Mendelian-inherited genomic markers for loci OnT23, OnT3 and OnC1 will be useful for association of alleles with bioassayed Bt toxin resistance phenotypes.
鳞翅目昆虫中肠表达的碱性丝氨酸蛋白酶在苏云金芽孢杆菌（Bt）原毒素转化为活性毒素的过程中发挥作用，转录本T23水平的降低与欧洲玉米螟对Dipel Bt制剂的抗性有关。从欧洲玉米螟中肠组织中分离出三组胰蛋白酶（OnT25、OnT23和OnT3）和两组类胰凝乳蛋白酶（OnC1和OnC2）的cDNA。种内分组基于cDNA相似性和肽系统发育。推导的丝氨酸蛋白酶显示出一个催化三联体（His、Asp和Ser；转录本OnT23a除外）、三个底物特异性决定残基和三对二硫键。RT-PCR表明所有转录本均在中肠中表达。OnT23、OnT3和OnC1位点的孟德尔遗传基因组标记将有助于将等位基因与生物测定的Bt毒素抗性表型相关联。
