Effects of elevated CO2 and transgenic Bt rice on yeast-like endosymbiote and its host brown planthopper

Abstract

The effects of elevated CO 2 (750 vs. 375μl/l) on population abundances and metabolism enzyme of AChE and protective enzymes of SOD, POD and CAT in brown planthoppers (BPH) Nilaparvata lugens, and on size and abundances of yeast-like endosymbiotes (YLES) were studied as BPH fed Bacillus thuringiensis (Bt) rice expressing pure Cry1Ab after successively two generations in open-top chambers. The results indicated that: (1) Brachypterous and macropterous subpopulations and total population increased with elevated CO 2 . Significant increases were found as BPH fed non-transgenic rice while only significant increase as macropterous-BPH fed Bt rice. (2) The responses of brachypterous and macropterous-BPH to Bt rice were different. Brachypterous-subpopulation significantly decreased (13.6%) while macropterous ones significantly increased (43.8%) as fed Bt rice relative to non-transgenic rice at elevated CO 2 . (3) Elevated CO 2 only significantly inhibited AChE activity as brachypterous-BPH fed non-transgenic rice. Significant increases in POD and SOD, and significant decrease in CAT were found as brachypterous-BPH fed Bt rice, while significant increases in CAT and significant decrease in POD were also observed as fed non-transgenic rice in elevated CO 2 relative to ambient CO 2 . (4) Bt rice significantly inhibited POD and SOD activity at ambient CO 2 , while only significantly enhanced SOD activity at elevated CO 2 . (5) Elevated CO 2 significantly decreased YLES per mg/head of brachypterous-BPH females while only significantly decreased YLES per mg/head as brachypterous-BPH males fed Bt rice. And there were significant differences in YLES width or length between females and males. Elevated CO 2 can markedly affect the symbiosis relationship between YLES and BPH through the bottom-up forcing on BPH physiological metabolism. And the damage inflicted by BPH on rice, irrespective of the presence of insecticidal genes, is predicted to be higher at elevated CO 2 . Furthermore, transgenic Bt rice can also exacerbate emigrating-macropterous-BPH occurring especially at elevated CO 2 .