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

The effects of elevated CO2 (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 CO2. 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 CO2. (3) Elevated CO2 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 CO2 relative to ambient CO2. (4) Bt rice significantly inhibited POD and SOD activity at ambient CO2, while only significantly enhanced SOD activity at elevated CO2. (5) Elevated CO2 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 CO2 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 CO2. Furthermore, transgenic Bt rice can also exacerbate emigrating-macropterous-BPH occurring especially at elevated CO2.