Jasmonate-induced 23kD protein, JIP-23, is involved in seed development of barley

We previously showed the high expression of a 23 kD protein (P23k) in germinating barley seeds. In this study, we examined whether P23k is involved in supplying sugar to developing barley grains. RT-PCR analysis revealed that, although P23k expression was not detectable in developing grain, the 23 kD jasmonate-induced protein (JIP-23) exhibited a high level of RNA expression. JIP-23 belongs to the same protein family as P23k. Its remarkable expression was specifically confirmed at early development stage when sugar import into the filling grains is active. Furthermore, in situ hybridization and immunohistochemistry showed that JIP-23 is localized to active tissues in sugar import, such as vascular tissues, nucellar projections, endosperm transfer cells, and inter nucellar cells. Taken together, these results suggest that JIP-23 is related to sugar import into filling grain of developing barley seeds. Hence, we propose that jasmonate may regulate the development of barley seed.