Recent and Projected Increases in Atmospheric CO2 Concentration Can Enhance Gene Flow between Wild and Genetically Altered Rice (Oryza sativa)

Lewis H. Ziska,Aaron K. Jackson,Howard L. Black,Martha B. Tomecek,David R. Gealy,Dorian Q. Fuller

doi:10.1371/journal.pone.0037522

Abstract

Although recent and projected increases in atmospheric carbon dioxide can alter plant phenological development, these changes have not been quantified in terms of floral outcrossing rates or gene transfer. Could differential phenological development in response to rising CO2 between genetically modified crops and wild, weedy relatives increase the spread of novel genes, potentially altering evolutionary fitness? Here we show that increasing CO2 from an early 20th century concentration (300 µmol mol−1) to current (400 µmol mol−1) and projected, mid-21st century (600 µmol mol−1) values, enhanced the flow of genes from wild, weedy rice to the genetically altered, herbicide resistant, cultivated population, with outcrossing increasing from 0.22% to 0.71% from 300 to 600 µmol mol−1. The increase in outcrossing and gene transfer was associated with differential increases in plant height, as well as greater tiller and panicle production in the wild, relative to the cultivated population. In addition, increasing CO2 also resulted in a greater synchronicity in flowering times between the two populations. The observed changes reported here resulted in a subsequent increase in rice dedomestication and a greater number of weedy, herbicide-resistant hybrid progeny. Overall, these data suggest that differential phenological responses to rising atmospheric CO2 could result in enhanced flow of novel genes and greater success of feral plant species in agroecosystems.

Highlights

Gene transfer between organisms is acknowledged as a significant influence on evolutionary change [1]
Tiller and panicle numbers, which provide the structural basis for floral initiation, rose to a greater extent for the wild relative to the cultivated populations doubling in response to the CO2 increase from 300 to 600 mmol mol21 (Figure 1)
Much of this work is focused on how anthropogenic disturbances are likely to change species range, demography [19], pollinator populations [20], and plant phenology [21], with little empirical evidence regarding outcrossing rates and gene transfer

Summary

Introduction

Gene transfer between organisms is acknowledged as a significant influence on evolutionary change [1]. A scientific understanding of biotic and abiotic factors that promote gene flow is of considerable interest. Occurring abiotic or physical phenomenon are understood; for example, the role of wind in pollen transfer for anemophilous plants, such as ragweed. In addition to these natural drivers, there is increasing recognition that gene flow can be altered by anthropogenic activities [3,4]. One prominent feature of anthropogenic disturbance that has been well quantified globally is the increase in atmospheric carbon dioxide, CO2. Since 1959, concentrations of atmospheric CO2 have increased from 318 to 392 mmol mol; and, depending on anthropogenic emission rates, may exceed 1000 mmol mol by the end of the century [5]

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Conclusion