Abstract
Expression analysis of β subunits of OSK in germinating rice seeds using semi-quantitative RT-PCR techniques revealed high expression of all the four β subunits during seed germination. Analysis of OSK gene promoters fused to GUS gene exhibited very high expression of GUS in the scutellum during germination. An attempt to purify the OSK complex from seeds during the germination stage resulted in isolation of a complex with SNF1-specific kinase activity and molecular weight similar to the proposed hetero-trimeric complex. However, visualization of phosphorylation pattern of the purified complex revealed that in addition to OSK auto-phosphorylation, additional proteins were phosphorylated. These could be substrates of OSK in the germinating seeds. Furthermore, suppression of OSK1, OSK3 and OSK4 during germination, using chemical-inducible RNAi resulted in delayed germination. The results of RNA-interference experiments also suggest that each species of OSK could have distinct function during seed germination.
