Required for normal embryo development, vegetative growth and transition to flowering. Regulates embryo growth, cell wall deposition, starch and sucrose degradation, but not cell differentiation. Involved in the regulation of glucose sensing and signaling genes during plant development. D-glucose 6-phosphate + UDP-alpha-D-glucose = alpha,alpha-trehalose 6-phosphate + H(+) + UDP Determined in transgenic tobacco plants expressing TPS1. Expressed in seedlings, leaves, roots, stems, flowers and siliques. Up-regulated during seed development. Low induction by sucrose after 24 hours. Down-regulated by dark incubation. The N-terminal part (1-88) has an inhibitory function on the enzymatic activity. Embryonic lethality. In the N-terminal section; belongs to the glycosyltransferase 20 family. In the C-terminal section; belongs to the trehalose phosphatase family.