Dowd Patrick F, Johnson Eric T, Pinkerton T Scott
Crop BioProtection Research Unit, Agricultural Research Service, U.S. Department of Agriculture, National Center for Agricultural Utilization Research, 1815 North University Street, Peoria, Illinois 61604, USA.
J Agric Food Chem. 2007 May 2;55(9):3421-8. doi: 10.1021/jf063562w. Epub 2007 Apr 7.
Insect chitin is a potential target for resistance plant proteins, but plant-derived chitin-degrading enzymes active against insects are virtually unknown. Commercial beta-N-acetylhexosaminidase (NAHA), a chitin-degrading enzyme from jack bean Canavalia ensiformis, caused significant mortality of fall armyworm Spodoptera frugiperda larvae at 75 microg/gm, but no significant mortality was noted with Aspergillus niger NAHA. Maize Zea mays callus transformed to express an Arabidopsis thaliana clone that putatively codes for NAHA caused significantly higher mortality of cigarette beetle Lasioderma serricorne larvae and significantly reduced growth rates (as reflected by survivor weights) of S. frugiperda as compared to callus that expressed control cDNAs. Tassels from model line Hi-II maize (Z. mays) plants transformed with the NAHA gene fed to S. frugiperda caused significantly higher mortality than tassels transformed to express glucuronidase; mortality was significantly correlated with NAHA expression levels detected histochemically. Leaf disks from inbred Oh43 maize plants transformed with the NAHA gene on average had significantly less feeding by caterpillars than null transformants. Leaf disks of Oh43 transformants caused significant mortality of both S. frugiperda and corn earworm Helicoverpa zea larvae, which was associated with higher expression levels of NAHA detected by isoelectric focusing, histochemically, or with antibody. Overall, these results suggest that plant NAHA has a role in insect resistance. Introduction of NAHA genes or enhancement of activity through breeding or genetic engineering has the potential to significantly reduce insect damage and thereby indirectly reduce mycotoxins that are harmful to animals and people.
昆虫几丁质是抗性植物蛋白的一个潜在靶点，但对昆虫具有活性的植物源几丁质降解酶实际上并不为人所知。商业β-N-乙酰己糖胺酶（NAHA），一种来自刀豆的几丁质降解酶，在浓度为75微克/克时可导致草地贪夜蛾幼虫显著死亡，但黑曲霉NAHA则未观察到显著的致死效果。转化以表达拟编码NAHA的拟南芥克隆的玉米愈伤组织，与表达对照cDNA的愈伤组织相比，可导致烟草甲幼虫的死亡率显著更高，并且草地贪夜蛾的生长速率显著降低（以存活幼虫体重反映）。用NAHA基因转化的模式品系Hi-II玉米（玉米）植株的雄穗喂食草地贪夜蛾，其死亡率显著高于转化以表达葡糖醛酸酶的雄穗；死亡率与通过组织化学检测到的NAHA表达水平显著相关。用NAHA基因转化的自交系Oh43玉米植株的叶盘，平均而言，毛虫的取食显著少于空转化体。Oh43转化体的叶盘可导致草地贪夜蛾和玉米螟幼虫显著死亡，这与通过等电聚焦、组织化学或抗体检测到的更高的NAHA表达水平相关。总体而言，这些结果表明植物NAHA在抗虫性中发挥作用。引入NAHA基因或通过育种或基因工程提高其活性，有可能显著减少昆虫损害，从而间接减少对动物和人类有害的霉菌毒素。
