Fig 2: Function and localization of FBP in response to fructose.(A) A simplified schematic diagram of the sucrose biosynthesis pathway. The fructose metabolic pathway includes fructokinase1 (FRK1), phosphofructokinase1 (PFK1), and putative fructose-1,6-bisphopatase (FBP). (B) FBP suppressed CAB2-fLUC activity. Leaf mesophyll protoplasts were cotransfected with CAB2-fLUC together with PFK1, FRK1, FBP (FBP_3 or FBP_4), or SSM (FBPS126AS127A). UBQ10-rLUC was cotransfected as a transfection control. An empty vector was used as a control for effectors. Protein expression was analyzed by protein blotting using an anti-HA antibody. (C) FBP was localized to both the nucleus and cytoplasm. Leaf mesophyll protoplasts were transfected with FBP-GFP and then incubated for 5 h or 18 h. GFP-only and EIN3-GFP constructs were transfected and examined as control proteins localized to the cytosol and nucleus, respectively. GFP was observed under a fluorescence microscope (200× magnification). Cell images were also taken under white light as a control.

Fig 3: Working model of hexose signaling network during A. thaliana early seedling development.HXK1/GIN2-dependent glucose signaling acts upstream of GIN1/ABA2, while FINS1/FBP functions downstream of GIN1/ABA2. Glucose signaling may also integrate into GIN1/ABA2 directly. Only a minor portion of fructose signaling may occur via GIN2/HXK1. Both hexose signals positively and negatively modulate ABA and ethylene responses, respectively.