| Research Abstract |
We have studied for three years to characterize proteins which were specific to either Cry1Ac susceptible P. xylostella or resistant one. These researches have been also done in relation to elucidate the kill mechanism of such B. thuringiensis insecticidal toxins. We have found that the content of oligosaccharylceramide which had longer sugar chain in midgut epithelial cell membrane in the resistant P. xylostella was less than half compared to that of susceptible one. Whereas, another membrane elements such as cholesterol glycerol etc were almost the same each other in both P. xylostella strains. We found a protein whose molecular size and pI were 40 kDa and 5.79, respectively. This was completely missing in Cry1Ac resistant P. xylostella. After completion of cloning of this protein this will be most suitable candidate to make ELISA system to monitor occurrence of resistant insect in field.
During these quests, we found various interesting facts. For example, Cry1Ab could kill most effectively the resistant P. xylostella among Cry1A toxins tested, but binding signal of Cry1Ab with apical membrane proteins was least. Cry1Ab bound with 230, 180, 127 and 105 kDa proteins which came from whole midgut membrane. On the other hand, when proteins came from apical-membrane of midgut tissue were used, binding signals were detected in 230, 110, 105, 60 and 55 kDa proteins. These suggested that 230, 110 and 105 kDa proteins which were detected in apical-membrane tissue must localize in apical membrane. Whereas, The proteins of 180 and 127 kDa which were detected in whole midgut tissue but missing in apical membrane materials seemed to localize in basolateral membrane of midgut tissue. These all results suggested that cadherin like protein with 180 kDa molecular size may be in basolateral membrane and could not be Cry toxin receptor.
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