Although an intermediate in flavonoid synthesis, t-chalcone is phytotoxic, causing mitochondrial disruption and apoptosis-like symptoms in plant roots at concentrations as low as 35 μM and causing bleaching of normally green shoot tissues. These phenomena suggest a unique mode of action. Transcriptome analysis technologies such as RNA-Seq are useful tools which may assist in the elucidation of the mode of action and molecular target(s) of a phytotoxin. Here we report the transcriptome changes in Arabidopsis seedlings during early exposure to t-chalcone. Our study is focused on the analysis of transcriptome profiling using RNAseq during the first 24 h of exposure (at 1, 3, 6, 12 and 24 h) to 21 μM t-chalcone (I50 dose), examining effects on Arabidopsis roots and shoots separately. Using a confidence of p = 0.001 and fold changes of ≥ 2.00, expression of 1357 and 498 genes was affected in roots and shoots, respectively. There was a general pattern of up-regulation for first 6 h after exposure, with down regulation at 12 and 24 h. In the shoots, down-regulation predominated for the first 3 h, followed by mostly up-regulation at 6 – 24 h. According to biological function, the affected genes were mainly transcription factors and genes associated with oxidative stress, heat shock proteins, xenobiotic detoxification, and ABA and auxin biosynthesis. Genes in the root associated with programmed cell death were up-regulated, as were promoters of chalcone synthase and chalcone isomerase. Although our results have not located a single target site, the results indicate that chalcone reaches its target site(s) in the root in less than an hour and that oxidative stress occurs soon afterward.

Probing the mode of action of the phytotoxin t-chalcone with RNAseq

254th National Meeting (2017)

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