Figure 2. Ntann12 function in tobacco root: a speculative model. (1) Light induces auxin synthesis in young tissues of the aerial part. (2) Auxin moves from shoot to root system via the PAT. (3) Auxin accumulation in root cells induces Ntann12 expression. (4) The increase of the level of cytosolic Ca2+ induced by auxin accumulation triggers recruitment of Ntann12 to negatively charged phospholipids. (5) Ntann12 interacts with other proteins (X1–X3) possibly via a phosphorylation-dependent regulation. (6) The protein complex reaches the cell nucleus. (7) The nuclear Ntann12 protein-complex may acts as a transcription factor to induce the expression of target genes that are required for the functioning of root system in daylight condition.