不同发育阶段谷蠹侵害对储藏小麦蛋白结构的影响

Effects of infestation by Rhyzopertha dominica in different development stages on wheat storage protein structure

为探索谷蠹在不同生长发育阶段对储藏小麦蛋白结构的影响,该文以谷蠹种虫感染后的小麦为研究对象,对谷蠹不同发育阶段(卵期、幼虫期、蛹期、成虫期)侵害后小麦中麦谷蛋白大聚合体(glutenin macropolymer,GMP)、沉降值、面筋蛋白持水力、蛋白二级结构、巯基(-SH)、二硫键(-S-S-)及面筋显微结构进行测定与分析。结果表明:在谷蠹发育的4个阶段,GMP、沉降值、β转角总体呈增加趋势,-SH、β折叠比例变化与之相反;面筋蛋白持水力、-S-S-和α螺旋比例总体呈先降后升趋势,无规卷曲比例变化则与之相反。卵期谷蠹危害较小,只有β转角和面筋蛋白持水力有显著变化(P<0.05);幼虫期和蛹期谷蠹危害严重,与相同试验条件下相应时期的无虫小麦对照样相比,GMP、无规卷曲和β转角比例及沉降值均显著增加(P<0.05),面筋蛋白持水力、-SH、-S-S-、α螺旋和β折叠显著减少(P<0.05)。面筋蛋白显微结构显示:随着谷蠹在小麦籽粒内部发育,面筋表面粗糙程度加重,微纤维状丝增多,结构疏松散乱,断裂严重,至成虫期时,面筋结构已无法识别,因此在实际储藏过程中不仅要关注成虫的数量,还应注意及时控制谷蠹的生长发育。

As a kind of the stored grain insect pests bored inside grains, the damages caused by Rhyzopertha dominica are very serious in the process of wheat storage, and it has severe impacts to wheat quality in many aspects, such as starch, lipid, protein, and so on. In order to explore the effects of infestation by Rhyzopertha dominica in different growth and development stages on wheat storage protein structure, and provide some references for the detection of wheat quality and the growth and development of stored grain insect pests in the process of wheat storage,the wheat infected by Rhyzopertha dominica was taken as the research material. The glutenin macropolymer content, Zeleny sedimentation value, gluten moisture capacity and protein secondary structure were inspected and analyzed, as well as the content of thiol（-SH） and disulfide bond（-S-S-）and gluten microstructures of wheat infected by Rhyzopertha dominica in different growth and development stages i.e. egg stage, larval stage, pupa stage and adult stage. The results showed that in the 4 growth and development stages of lesser grain borer, the Zeleny sedimentation value, glutenin macropolymer conten and β-turn had an increasing trend in general, while the content of-SH and β-pleated sheet showed a completely opposite change trend. The gluten water absorption capacity, and the content of-S-S- and α-helix showed a downward trend first and then an upward trend, and the change of random curl content showed an opposite trend. The lesser grain borer in the egg stage did less harm to wheat storage protein structure, and just the gluten water absorption capacity and β-turn content had a great change（P〈0.05）, while the lesser grain borer in larval stage and pupa stage had a serious damage to wheat storage protein structure. Compared to the control samples of the insect-free wheat with the relevant infection stages under the same experimental conditions, the Zeleny sedimentation value, content of glutenin macropolymer, β-turn and random curl of wheat infected by lesser grain borer in the larval and pupa stages increased significantly（P〈0.05）, but the gluten water absorption capacity, content of-SH and-S-S-, α-helix and β-pleated sheet decreased（P〈0.05）. In addition, the microstructure analysis results showed that the micro fiber filament increased and the surface of gluten got rough, the structure got loose and scattered, and the structure fracture became more and more severe with the growth and development of lesser grain borer. Until the stage of adult, some microstructure of gluten could not even be identified. All the experiment results show that the damages on wheat protein structure are severe with the growth and development of lesser grain borer inside wheat granules. Accordingly, timely control on lesser grain borer is necessary and it will reduce the damage to wheat storage protein structure before infestation by Rhizopertha dominica in the larval and pupa stages. The research results provide the reference for the control of the lesser grain borer for the wheat during the storage.