Abstract
CO2 responsive CCT protein (CRCT) is a positive
regulator of starch synthesis related genes such as ADP-glucose
pyrophosphorylase large subunit 1 and starch branching enzyme Iparticularly in the leaf sheath of rice (Oryza sativa L.). The
promoter GUS analysis revealed that CRCT expressed
exclusively in the vascular bundle, whereas starch synthesis related
genes were expressed in different sites such as mesophyll cell and
starch storage parenchyma cell. However, the chromatin
immunoprecipitation (ChIP) using a FLAG-CRCT overexpression line and
subsequent qPCR analyses showed that the 5’-flanking regions of these
starch synthesis-related genes tended to be enriched by ChIP, suggesting
that CRCT can bind to the promoter regions of these genes. The monomer
of CRCT is 34.2 kDa, however CRCT was detected at 270 kDa via gel
filtration chromatography, suggesting that CRCT forms a complex in
vivo . Immunoprecipitation and subsequent MS analysis pulled down
several 14-3-3-like proteins. A yeast two-hybrid analysis and
bimolecular fluorescence complementation assays confirmed the
interaction between CRCT and 14-3-3-like proteins. Although there is an
inconsistency in the place of expression, this study provide important
findings regarding the molecular function of CRCT to control the
expression of key starch synthesis-related genes.