The effect of sub-environment and external influence on Turing pattern formation in two-layer coupled reaction-diffusion systems is studied. When the two layers are in different sub-environments, not only can classical Turing patterns be either induced or inhibited, but also special Turing patterns with different temporal characters may appear. This means Turing pattern formation in the coupled systems may result from coupling. When one of the sub-layers is under external influence, Turing patterns in the coupled systems exhibit stronger ability to survive than in the single-layer cases. Since bilayer membranes or mutilayer tissues are often found, this work is of practical significance for investigations of pattern formation in complex biological systems. (c) 2006 Elsevier B.V. All rights reserved.