Microarray analysis of genes differentially expressed in melatonin-rich transgenic rice expressing a sheep serotonin N-acetyltransferase.

Transgenic rice plants overexpressing a sheep serotonin N-acetyltransferase led to an enhanced production of melatonin with various physiological effects, including seminal root elongation and resistance against cold and oxidative stress, which raises the possibility that melatonin may alter gene expression profiles in the transgenic rice. Therefore, we performed a microarray analysis to investigate the regulatory role of melatonin using the melatonin-rich transgenic rice. We identified 260 and 204 genes that were up- or downregulated in the melatonin-rich transgenic rice when compared with the wild type. Of these, 20 upregulated genes were identified in the seedlings of melatonin-rich rice at more than twice the levels in the wild type (P < 0.05), while 23 downregulated genes were also detected. The representative upregulated genes included caleosin, a Ca(2+) -binding oil-body surface protein involved in the degradation of lipids stored in oil bodies and various signaling proteins such as a cyclin F-box protein and leucine-rich repeat protein. In contrast, jasmonate-induced protein, senescence-associated protein, and polygalacturonase were included in the downregulated gene group. These results suggest that melatonin has an important role in modulating a wide range of gene expression, reflecting its pleiotropic physiological roles in plant growth and development.