Gao Xiwu

Induction of Phenylalanine ammonia-lyase and lipoxtgenase in cotton seedlings by mechanical wounding and aphid infestation∗

It has been suggested that infestation of plants causes increases in the activities of phenylalanine ammonia-lyase (PAL) and lipoxygenase (LOX), key enzymes in the phenolic compounds synthesis pathway and the octadecanoid pathway, respectively. The purpose of this work is to investigate whether the infestation of cotton aphid (Aphis gossypii) and mechanical wound can cause the induction of PAL and LOX activities in cotton seedlings, and whether the induction occurs in healthy seedlings growing nearby the attacked ones. The specific activities of PAL and LOX were measured using spectrophotometric method after aphid infestation and mechanical wounding. Result indicated that PAL activity and LOX activity were greatly induced by mechanical wounding and aphid infestation in cotton seedlings. The induction of PAL and LOX occurred not only in wounded and infested seedlings but also in intact healthy seedlings growing nearby. After exposed to the aphid infestation-induced volatiles, the specific activity of PAL in cotton seedlings increased by 6% at 24 h, 80% at 48 h, 235% at 72 h compared to the control, and the specific activity of LOX increased by 18% at 24 h, 34% at 48 h, 24% at 72 h, respectively. In comparison, the specific activity of PAL in unwounded seedlings exposed to wound-induced volatiles increased by 0.0 at 24 h, 200% at 48 h, 164% at 72 h, respectively and the specific activity of LOX increased by 28% at 24 h, 37% at 48 h, 8% at 72 h, respectively. It suggests that the induced volatiles are involved in plant-plant communication as airborne transferred signals.

Application of Liquid Chromatography‐Time‐of‐Flight‐Mass Spectrometry for the Analysis of Urea Herbicides Residues in Soybean

Abstract In this work, a new multiresidue methodology using liquid chromatography‐time‐of‐flight‐mass spectrometry (LC‐TOF‐MS) for the quantitative analysis of pesticide residues has been developed. The accurate mass was obtained in different levels (from 0.02 to 0.10 mg · kg−1) and accuracy errors was lower than 3 ppm, which is well within the accepted limits for target confirmation. Linearity of response ranged from 0.01 mg · kg−1 to 1 mg · kg−1. The average recoveries of nine urea herbicides in spiked soybean ranged from 70.16% to 114.41%, and the relative standard deviations (RSD) were between 2.22% and 11.12%. Limits of detection (LOD) were between 0.00003 and 0.009 mg · kg−1. The results indicated that the method developed was easier, faster, and more sensitive. It also demonstrated that this method could meet the requirements for simultaneous determination of urea herbicides in soybean. This study provides valuable evidence for that LC‐TOF‐MS method has the potential in screening multi‐residue pesticides in soybean.

Tissue-specific expression of gluthathione S-transferases induced by 2-tridecanone or quercetin in cotton bollworms, Helicoverpa armigera (Hübner)*

Abstract The tissue-specific expression of glutathione S-transferases (GSTs) in the cotton bollworm and the expression level induced by 2-tridecanone and quercetin were examined using the methods of biochemistry and the quantitative PCR. The relative expression level of GST mRNA was unanimous with the GSTs activity conjugaging with 1-chloro-2, 4-dimitro-benzene (CDNB) in fat bodies, midguts, heads and integuments of cotton bollworms. The GSTs activity in fat bodies was the highest, then midguts, heads and integuments in turn, which was in consistent with the relative expression level of GST mRNA. The specific activity of GSTs and the relative expression level of GST mRNA could be significantly induced by 2-tridecanone and quercetin, and after the induction the order of the GSTs activity and relative expression level of GST mRNA in the above four tissues in cotton bollworms was not different from the control. The induction of GSTs by 2-tridecanone was stronger than by quercetin in all four tissues, which w...

A COMPARISON OF SENSITIVITY TO INHIBITOR AMONG ACETYLCHOLINESTERASE (AChE) MOLECULAR FORMS OF RESISTANT AND SUSCEPTIBLE STRAINS IN HELICOVERPA ARMIGERA

Abstract The sensitivity of 2.8s and 8.7s acetylcholinesterase (AChE) to eserine sulfate is significantly lower in resistant (R) strain than in susceptible (S) strain in five AChE forms isolated by sucrose gradient centrifugation from cotton bollworm, Helicoverpa armigera. There are 186 and 85 times of difference in heads of adults and 1010 and 105 times of difference in heads of larvae based on a comparison of I50 values for 2.8s and 8.7s forms respectively. The sensitivity of 5.3s form of AChE to eserine sulfate shows 123 times of difference between R and S strains in larvae, however no difference in adults. The above results indicate that insensitive 2.8s, 8.7s and 5.3s forms of AChE may play an important role in the resistance of cotton boll‐worm to organophosphate and carbamate insecticides.