Mesh.uv

Description

The base texture coordinates of the Mesh.

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour
{
    void Start()
    {
        Mesh mesh = GetComponent<MeshFilter>().mesh;
        Vector3[] vertices = mesh.vertices;
        Vector2[] uvs = new Vector2[vertices.Length];

        for (int i = 0; i < uvs.Length; i++)
        {
            uvs[i] = new Vector2(vertices[i].x, vertices[i].z);
        }
        mesh.uv = uvs;
    }
}

Note: Texture coordinates have to be modified or created externally from the Mesh. In the script example above, the uvs is created as a new array, then the texture coordinates are assigned to that array. Once these are assigned, the array is assigned to the Mesh.