Transcriptome profiling of activation of isoprene emission in a tropical tree, Ficus septica. Ficus septica

Isoprene is the most abundant non-methane biogenic volatile organic carbon in the atmosphere, originating mainly from land plants. The tropical tree species, Ficus septica (Rosales: Moraceae), has been shown to cease isoprene emission when exposed to temperatures of 12 ?C or lower, but subsequent exposure to temperatures of 30 ?C or greater can reactivate the isoprene production after a full day. To elucidate the dynamics of gene expression underlying this phenomenon, we conducted transcriptome profiling of F. septica during this process by using a next generation sequencing platform, SOLiD technology, and quantitative real-time PCR (qRT-PCR). The transcriptome sequencing yielded 9.9 Gbp data assembled into 50,596 transcript sequences, in which genes involved in the central metabolic pathways were comprehensively identified. Quantification of gene expression levels in the pathways by SOLiD and qRT-PCR indicated that increased gene expression level of isoprene synthase (ispS) regulated the temperature dependent inactivation and reactivation of isoprene emission. In addition to ispS, genes involved in substrate supply and hormone signalling were upregulated one day after temperature elevation, implying an upstream regulation of isoprene emission following perception of ambient temperature change.