Protein-protein interactions of tandem affinity purification-tagged protein kinases in rice

Forty- one rice cDNAs encoding protein kinases were fused to the tandem affinity purification ( TAP) tag and expressed in transgenic rice plants. The TAP- tagged kinases and interacting proteins were purified from the T1 progeny of the transgenic rice plants and identified by mass spectrometry. Ninety- five percent of the TAP-tagged kinases were recovered. Fifty- six percent of the TAP- tagged kinases were found to interact with other rice proteins. A number of these interactions were consistent with known protein complexes found in other species, validating the TAP- tag method in rice plants. Phosphorylation sites were identified on four of the kinases that interacted with either 14- 3- 3 proteins or cyclins.