Abstract
Plants have mechanisms to regulate C and N metabolism and growth in response to the C/N ratio in cells and/or environments. Although a few proteins involved in this mechanism was identified in recent studies, the mechanism is largely unknown yet. BT proteins are plant-specific proteins that possess two protein interaction domains, the BTB and TAZ domains, and they are proposed to function as scaffold proteins in protein complexes. In Arabidopsis thaliana, there are 5 genes encoding BT proteins. The expressions of BT1 and BT2 are repressed by sugar but induced by nitrate. Here we show nuclear localization of BT1 and BT2 proteins. We also show the severer glucose inhibition of greening and the weaker antagonistic action of nitrate to glucose in the bt1 and bt2 mutants. Furthermore, we found that the phenotype was much severer in the bt1 bt2 double mutant, implying roles of BT1 and BT2 in the mechanism underlying C/N balance responses. We are currently attempting to identify proteins that interact with BT proteins and proteins of the complexes including BT proteins by a proteomic approach.
