Transcriptome profiling reveals ethylene production by reactive oxygen species in trichloroisocyanuric acid-treated rice seeds

Reactive oxygen species (ROS) have been extensively suggested to stimulate ethylene production. However, the molecular mechanism by which ROS stimulate ethylene production remains largely unclear. Here, transcriptome profiling was used to verify if ROS could stimulate ethylene production via direct formation of ethylene from ROS. Trichloroisocyanuric acid (TCICA) can stimulate seed germination in rice. When transcriptome profiling was performed to determine the molecular responsiveness of rice seeds to TCICA, TCICA was initially proven to be a ROS-generating reagent. A total of 300 genes potentially responsive to TCICA treatment were significantly annotated to cysteine, and the expression of these genes was significantly upregulated. Nonetheless, the levels of cystine did not exhibit significant changes upon TCICA exposure. Cystine was then proven to be a substrate that reacted with TCICA to form ethylene under FeSO4 conditions. Moreover, 7 of 22 genes responsive to TCICA were common with the hydrogen peroxide (H2O2)-responsive genes. Ethylene was then proven to be produced from cysteine or cystine by reacting with H2O2 under FeSO4 condition, and the hydroxyl radical (OH-) was proposed to be the free radical species responsible for ethylene formation under FeSO4 condition. These results provide the first line of evidence that ethylene can be produced from ROS in a non-enzymatic manner, thereby unveiling one new molecular mechanism by which ROS stimulate ethylene production and offering novel insights into the crosstalk between ethylene and ROS.