Expression analysis of genes enriched in the pulvinus of <i>Lotus japonicus</i>

The pulvinus is a unique motor organ found in leguminous plants. The motor cells surrounding the central vascular bundle of the pulvinus are divided into extensor and flexor halves. The asymmetric change in turgor pressure of the motor cells of the extensor/flexor halves is the driving force behind nyctinastic leaf movement. Omics analysis has recently revealed genes involved in pulvinar development and function, but the molecular mechanism orchestrating the pulvinar movement remains elusive. In this study, we investigated genes predominantly and highly expressed in the pulvinus to find out key genes involved in the regulation of nyctinastic movement. Gene expression in both the pulvinus and stem at dawn and dusk was examined using RNA sequencing analysis. As a result, several genes were identified that preferentially change in expression in the pulvinus at dawn. Among the genes, we first focused on genes that are more highly expressed in the pulvinus than in the stem and validated the results by reverse transcription-polymerase chain reaction (RT-PCR). We further focused on auxin-related genes, as auxin was found to be preferentially expressed in the pulvinus and has been reported to be involved in the regulation of nyctinastic leaf movement. Quantitative real-time PCR and in situ hybridization analyses revealed that at least two auxin-related genes, <i>IAA19</i>/<i>FLS1</i>, are dominantly expressed in the pulvinus. Thus, we provided a new dataset to identify genes involved in the regulation of nyctinastic leaf movement.