Isolation and Characterization of Triacontanol-Regulated Genes in Rice (Oryza sativa L.): Possible Role of Triacontanol as a Plant Growth Stimulator

Triacontanol (TRIA) is a saturated long-chain alcohol that is known to have a growth promoting activity when exogenously supplied to a number of plants. In this study, dry weight, protein and chlorophyll contents of rice seedlings were increased by foliar application of TRIA. Leaf net photosynthesis rate (Pn) was increased very quickly and persistently at a given photon flux density (PFD). The TRIA-regulated genes in rice were isolated from cDNA library by differential screening with probes generated from the forward- and reverse-suppression subtractive hybridization (SSH) populations and confirmed by Northern blot. Sequence analysis revealed that most of the up-regulated genes encoded the photosynthetic and photorespiratory proteins. Two down-regulated genes were identified as those encoding an ABA- and stress-related protein and a wounding-related protein. These results suggested that TRIA up-regulated the photosynthesis process and suppressed stresses in rice plants. Time-course profiles of expression of rbcS isogenes suggested the complex mechanisms involved in the regulation of photosynthesis promoted by TRIA.