The disaccharide sucrose cannot be utilized directly; rather, it is irreversibly hydrolyzed by invertase to the hexoses glucose and fructose, to shape plant growth. In this context, glucose controls the stability of the transcription factor Ethylene-Insensitive3 (EIN3) via the function of Hexokinase1 (HXK1), a glucose sensor. Thus, invertase, especially the major neutral cytosolic invertase (CINV), constitutes a key point of control for plant growth. However, the cognate regulatory mechanisms that modulate CINV activity remain unclear. Here, we demonstrate that in Arabidopsis thaliana EIN3 binds directly to both the promoters of Production of Anthocyanin Pigment1 (PAP1) and Phosphatidylinositol Monophosphate 5-Kinase 9 (PIP5K9), repressing and enhancing their expression, respectively. Subsequently, PAP1 binds directly to and promotes transcription from the Cytosolic Invertase1 (CINV1) promoter, while PIP5K9 interacts with and negatively regulates CINV1. The accumulated CINV1 subsequently hydrolyzes sucrose, releasing the sequestered signaling cue, glucose, which has been shown to negatively regulate the stability of EIN3 via HXK1. We conclude that a CINV1-glucose-HXK1-EIN3-PAP1/PIP5K9-CINV1 loop contributes to the modulation of CINV1 activity regulating root growth by glucose signaling.
- ethylene-insensitive3 (EIN3)
- production of anthocyanin pigment1 (PAP1
- hexokinase1 (HXK1)
- cytosolic isoforms (CINV),
- phosphatidylinositol monophosphate 5-kinase 9 (PIP5K9)
- root growth
- glucose signal loop