Transcriptome and binding data indicate that citral inhibits single strand DNA-binding proteins

BCKGROUND: Citral is a phytochemical monoterpene aldehyde that has been reported to be phytotoxic to a number of plant species. When treated in a solution, citral was phytotoxic to barnyard grass, wild oat, redroot pigweed, ribwort, lettuce, and barley, but not active on soybean, rice, maize, wheat, field bindweed, or common purslane. To investigate the mechanism of citral phytotoxicity in plant, we performed transcriptome analysis experiments using the model plant Arabidopsis. RESULTS: The concentration of citral that inhibited growth by 50% (202 μM) down regulated transcription of 9156 and 5541 genes in roots and shoots, respectively, at the p ≤ 0.001 level after 1 h. Only 56 and 62 genes in roots and shoots, respectively, were upregulated. In the roots, these effects dissipated after 3 and 6 h, but similar effects began again at 12 and continued until 24 h. In the shoots, the down regulation increased at 3 h (6239 genes downregulated, vs. 66 upregulated) with the effect decreasing at from 6 to 24 h, with only 1 gene downregulated at 24 h. Of all genes affected in roots at 1 h and shoots at 3 h (times of greatest effect), 6.5 and 9.2 %, respectively, of affected genes were for DNA and RNA binding functions. Genes for single strand DNA binding proteins (SSBP) WHY1, WHY 2 and WHY3 were strongly downregulated in the shoot up until 12 h after citral exposure. CONCLUSIONS: Molecular docking analysis suggests a potential binding model of citral with the single-strand binding proteins (SSBPs) WHY1, WHY2, and WHY3, as well as with other transcription factors such as MYC-2, ANAC, and SCR-SHR. Such an effect could account for the profound and unusual effects on down-regulation of gene transcription. Overall design: Arabidopsis seedlings (14 days-old) were treated with citral at IC50 concentration (202 µM). After treatment, plants were incubated for 0, 1, 3, 6, 12 and 24 h. Three replicate samples were collected from control plants (0.1% EtOH) and treated plants for each time point.