Trehalose 6-phosphate and hormone signalling crosstalk

Hormone and sugar signalling pathways have evolved from intermediates of central metabolic flow into conserved core interacting regulatory modules that balance resource acquisition and growth. Hormones play extensive yet often specialised functions, whereas sugar signalling through trehalose 6-phosphate (T6P) is active throughout plant development to integrate sucrose availability into all aspects of growth and physiology. Interaction between T6P and hormones is an emerging area and the focus of this review. The best mechanistically understood interactions are between T6P and auxin, strigolactones and abscisic acid (ABA), with reciprocal interaction for auxin-T6P and ABA-T6P. These interactions regulate root and shoot branching, seed development and stomatal function and converge on SnRK1 and TOR as a major integrating hub. Analysis of cis-acting regulatory elements in the promoters of Arabidopsis trehalose phosphate synthase (TPS) and trehalose phosphate phosphatase (TPP) genes confirms auxin and ABA as major regulators of TPSs and TPPs with an indication also of strong regulation by methyl jasmonate. Intervention in crop improvement will come from understanding how to disrupt the productivity-survival trade off regulated by T6P-hormones that has evolved in the natural environment.