Induction of P450 genes in Nilaparvata lugens and Sogatella furcifera by two neonicotinoid insecticides

Nilaparvata lugens and Sogatella furcifera are two primary planthoppers on rice throughout Asian countries and areas. Neonicotinoid insecticides, such as imidaclo- prid （IMI）, have been extensively used to control rice planthoppers and IMI resistance consequently occurred with an important mechanism from the over-expression of P450 genes. The induction of P450 genes by IMI may increase the ability to metabolize this insecticide in planthoppers and increase the resistance risk. In this study, the induction of P450 genes was compared in S. furcifera treated with IM] and nitromethyleneimidazole （NMI）, in two planthopper species by IMI lethal dose that kills 85% of the population （LD85）, and in N. lugens among three IMI doses （LD15, LD50 and LD85）. When IMI and NMI at the LD85 dose were applied to S. furcifera, the expression changes in most P450 genes were similar, including the up-regulation of nine genes and down-regulation of three genes. In terms of the expression changes in 12 homologous P450 genes between N. lugens and S. furcifera treated with IMI at the LD85 dose, 10 genes had very similar patterns, such as up-regulation in seven genes, down-regulation in one gene and no significant changes in two genes. When three different IMI doses were applied to N. lugens, the changes in P450 gene expression were much different, such as up-regulation in four genes at all doses and dose-dependent regulation of the other nine genes. For example, CYP6AY1 could be induced by all IMI doses, while CYP6ER1 was only up-regulated by the LDs0 dose, although both genes were reported important in IMI resistance. In conclusion, P450 genes in two planthopper species showed similar regulation patterns in responding to IMI, and the two neonicotinoid insecticides had similar effects on P450 gene expression, although the regulation was often dose-dependent.

Expression of cytochrome P450 CYP81A6 in rice: tissue specificity, protein subcellular localization, and response to herbicide application

The cytochrome P450 gene CYP81A6 confers tolerance to bentazon and metsulfuron-methyl, two selective herbicides widely used for weed control in rice and wheat fields. Knockout mutants of CYP81A6 are highly susceptible to both herbicides. The present study aimed to characterize the CYP81A6 expression in rice. Quantitative real-time polymerase chain reaction（PCR） analyses demonstrated that foliar treatment of bentazon（500 mg/L） greatly induced expression of CYP81A6 in both wild-type（Jiazhe B） and its knockout mutant（Jiazhe m B）： a 10-fold increase at 9 h before returning to basal levels at 24 h in Jiazhe B, while in the mutant the expression level rose to 20-fold at 12 h and maintained at such high level up to 24 h post exposure. In contrast, metsulfuron-methyl（500 mg/L） treatment did not affect the expression of CYP81A6 in Jiazhe B within 80 h; thereafter the expression peaked at 120 h and returned gradually to basal levels by Day 6. We suggest that a metabolite of metsulfuron-methyl, 1H-2,3-benzothiazin-4-（3H）-one-2,2-dioxide, is likely to be responsible for inducing CYP81A6 expression, rather than the metsulfuronmethyl itself. Use of a promoter-GUS reporter construct（CYP81A6Pro：：GUS） demonstrated that CYP81A6 was constitutively expressed throughout the plant, with the highest expression in the upper surfaces of leaves. Subcellular localization studies in rice protoplasts showed that CYP81A6 was localized in the endoplasmic reticulum. These observations advance our understanding of CYP81A6 expression in rice, particularly its response to the two herbicides.

Effects of CeCl_3 and LaCl_3 on callus and root induction and the physical response of tobacco tissue culture

La3＋ and Ce3＋ have positive effects on plant growth and production. Although it is well known that rare earth elements promote cell growth. The biological effects of La^（3＋） and Ce^（3＋） on callus, shoot and root induction in tobacco are still unclear. The relationships among callus induction, rooting, enzyme activities and stomatal characteristics in tobacco are unknown. The objectives of this study were to identify the relationships between the induction of calluses, shoots, roots, stomata and enzyme activities. The induction percentages of calluses, buds, roots were recorded at 5,10,15, 20 and 25 days after La^（3＋） and Ce^（3＋） treatments. Peroxidase isoenzyme activity was determined by electrophoresis. The characteristics of the stomata were observed under an optical microscope. Our results show that low concentrations of Ce^（3＋）（〈15 mg/L） result in increases in the induction percentages of calluses,buds and roots, but La^（3＋）（〉5 mg/L） inhibits the induction of calluses, buds and roots. There are more peroxidase isoenzyme bands in Ce^（3＋） treatments than in La^（3＋） treatments. This is consistent with the induction percentages of calluses,buds and roots in Ce^（3＋） and La^（3＋） treatments. High enzyme activities may promote the induction of calluses, buds and roots. The stomata area and stomata number of leaves are significantly different between La^（3＋） treatments and Ce^（3＋） treatments. La^（3＋） improves the stomata area and number. Based on these results, we speculate that La^（3＋） may promote the development of the photosynthetic system. Ce^（3＋）may promote tobacco growth and rooting by improving enzyme activities.