Sound wave affects the expression of ethylene biosynthesis-related genes through control of transcription factors RIN and HB-1

We previously reported that sound wave treatment (1 kHz) delays fruit ripening in tomato ( Solanum lycopersicum ), affecting the expression of ethylene biosynthesis-related genes encoding 1-aminocyclopropane-1-carboxylic acid (ACC) synthases (ACS) and ACC oxidases (ACO). In this study, we investigated the activity of the transcription factors RIN and HB-1, which function in the ethylene biosynthetic pathway, in response to sound treatment. To investigate whether RIN and HB-1 directly activate the transcription of ACS and ACO , we performed transcriptional activation analysis in Arabidopsis thaliana leaf protoplasts, transiently expressing RIN or HB - 1 and using reporter constructs with promoters of the tomato ACS and ACO genes. Activation of the endogenous AtACS and AtACO genes was also measured by qPCR. The RIN- and HB-1-induced expression of these genes decreased, but the HB-1-induced expression of some genes increased after sound treatment. To confirm these results, we performed transient assays in Nicotiana tabacum , which produced results similar to those observed in Arabidopsis. The major ethylene biosynthesis-related genes harbor a CArG-box as a RIN-binding motif. These findings indicate that RIN and HB-1 affect the expression of ethylene biosynthesis-related genes in response to sound treatment, and they suggest that RIN may regulate the ethylene biosynthesis-related genes by binding to their CArG-boxes.