We study computational complexity of learning read-once formulas over different boolean bases. In particular we design a polynomial time algorithm for learning read-once formulas over a threshold basis. The algorithm works in time $O(n^3)$ using $O(n^3)$ membership queries. By the result of [Angluin, Hellerstein, Karpinski, 1989] on the corresponding unate class of boolean functions, this gives a polynomial time learning algorithm for arbitrary read-once formulas over a threshold basis with negation using membership and equivalence queries. Furthermore we study the structural notion of nondegeneracy in the threshold formulas generalizing the result of [Heiman, Newman, Wigderson, 1990] on the uniqueness of read-once formulas over different boolean bases and derive a negative result on learnability of nondegenerate read-once formulas over the basis (AND,~XOR).