DUBAI — This year, for the first time among the nearly 300 galleries fine-tuning their last-minute preparations for Art Basel, there are two galleries from the Gulf region: Green Art Gallery and Gallery Isabelle van den Eynde. The inclusion of the galleries, both from Dubai, has signaled for many a sign of the maturation of the Middle Eastern art scene and its increasing global presence. “The fact that you have two galleries from the U.A.E. points to the growth of the region in terms of its artists, galleries, institutions and private collectors,” said Marc Spiegler, co-director of Art Basel, which opens Thursday and runs through June 17.