  In the holographic model of QCD, theta dependence sharply changes at the
point of confinement deconfinement phase transition. In large N QCD such a
change in theta behavior can be related to the breakdown of the instanton
expansion at some critical temperature T_c. Associating this temperature with
confinement-deconfinement phase transition leads to the description of the
latter in terms of dissociation of instantons into the fractionally charged
instanton quarks. To elucidate this picture, we introduce the nonvanishing
chiral condensate in the deconfining phase and assume a specific lagrangian for
the eta' field in the confining phase. In the resulting picture the high
temperature phase of the theory consists of the dilute gas of instantons, while
the low temperature phase is described in terms of freely moving fractional
instanton quarks.
