We study the moduli space M of torsion-free G2-structures on a fixed compact manifold M 7 , and define its associated universal intermediate Jacobian J . We define the Yukawa coupling and relate it to a natural pseudo-Kähler structure on J .We consider natural Chern-Simons type functionals, whose critical points give associative and coassociative cycles (calibrated submanifolds coupled with Yang-Mills connections), and also deformed Donaldson-Thomas connections. We show that the moduli spaces of these structures can be isotropically immersed in J by means of G2-analogues of Abel-Jacobi maps.