Signaling pathways, specifically mitogen-activated protein kinase (MAPK) cascades, have been implicated in the regulation of stress and developmental signals in plants. Here, we report the characterization of a rice (Oryza sativa L. cv. TN-67) MAPK gene, OsMAPK3, isolated by screening a sugar-starved treated rice cell cDNA library. The OsMAPK3 gene was abundantly expressed in mature leaves and panicles of 3-month-old plants, but poorly in young leaves. Its developmental regulation was suggested by the fact that OsMAPK3 mRNA levels changed during leaf differentiation and root development. Furthermore, the amount of this transcript increased markedly in sugar-starved or mannose-fed cells.
