Impacts of elevated CO2 on exogenous Bacillus thuringiensis toxins and transgene expression in transgenic rice under different levels of nitrogen

Shoulin Jiang,Fajun Chen,Yongqing Lu,Guijun Wan,Teng Li,Yang Dai,Lei Qian,Adnan Bodlah Muhammad,Megha N Parajulee

doi:10.1038/s41598-017-15321-9

Shoulin Jiang, Fajun Chen + Show 7 more

Open Access

https://doi.org/10.1038/s41598-017-15321-9

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Abstract

Recent studies have highlighted great challenges of transgene silencing for transgenic plants facing climate change. In order to understand the impacts of elevated CO2 on exogenous Bacillus thuringiensis (Bt) toxins and transgene expression in transgenic rice under different levels of N-fertilizer supply, we investigated the biomass, exogenous Bt toxins, Bt-transgene expression and methylation status in Bt rice exposed to two levels of CO2 concentrations and nitrogen (N) supply (1/8, 1/4, 1/2, 1 and 2 N). It is elucidated that the increased levels of global atmospheric CO2 concentration will trigger up-regulation of Bt toxin expression in transgenic rice, especially with appropriate increase of N fertilizer supply, while, to some extent, the exogenous Bt-transgene expression is reduced at sub-N levels (1/4 and 1/2N), even though the total protein of plant tissues is reduced and the plant growth is restricted. The unpredictable and stochastic occurrence of transgene silencing and epigenetic alternations remains unresolved for most transgenic plants. It is expected that N fertilization supply may promote the expression of transgenic Bt toxin in transgenic Bt rice, particularly under elevated CO2.

Highlights

Global atmospheric CO2 concentrations have been increasing at an accelerating rate from 280 ppm before industrialization to 402 ppm in recent years (Mauna Loa Observatory: NOAA-ESRL), and are anticipated to reach at least 550 ppm by the year 20501
The results showed that the aboveground and belowground biomasses of transgenic Bacillus thuringiensis (Bt) rice were significantly affected by N supply rates (Table 4)
The aboveground and belowground biomass of transgenic Bt rice was increased by elevated CO2 in comparison with ambient CO2 at the 2 N level, but the effect of elevated CO2 on rice seedling biomass decreased at sub-optimal levels of N (i.e., 1/8, 1/4 and 1/2 N), with a conspicuous sharp decrease at 1/2 N (Fig. 2)

Summary

Introduction

Global atmospheric CO2 concentrations have been increasing at an accelerating rate from 280 ppm before industrialization to 402 ppm in recent years (Mauna Loa Observatory: NOAA-ESRL), and are anticipated to reach at least 550 ppm by the year 20501. We simulated the future global atmospheric CO2 concentrations to determine how elevated CO2 affects the Bt-transgene methylation and Bt toxins expression in transgenic Bt rice under different rates of N-fertilizer augmentation. The measurement of foliar Bt toxins and total soluble proteins of transgenic Bt rice.

Results

Conclusion