Functional characterization of plant volatile organic compound (VOC) biosynthetic genes and elucidation of the biological function of their products often involve the screening of large numbers of plants from either independent transformation events or mapping populations. The low time resolution of standard gas chromatographic methods, however, represents a major bottleneck for in planta genetic characterization of VOC biosynthetic genes. Here we present a fast and highly-sensitive method for the high-throughput characterization of VOC emission levels/patterns by coupling a Proton Transfer Reaction Time-of-Flight Mass Spectrometer to an autosampler for automation of sample measurement. With this system more than 700 samples per day can be screened, detecting for each sample hundreds of spectrometric peaks in the m/z 15-300 range. As a case study, we report the characterization of VOC emissions from 116 independent Arabidopsis thaliana lines transformed with a putative isoprene synthase gene, confirming its function also when fused to a C-terminal 3×FLAG tag. We demonstrate that the method is more reliable than conventional characterization of transgene expression for the identification of the most highly isoprene-emitting lines. The throughput of this VOC screening method exceeds that of existing alternatives, potentially allowing its application to reverse and forward genetic screenings of genes contributing to VOC emission, constituting a powerful tool for the functional characterization of VOC biosynthetic genes and elucidation of the biological functions of their products directly in planta.
Keywords: Arabidopsis thaliana; Genetic screening; Isoprene; PTR-MS; Time-of-flight; VOCs.