Rotate Texture Over Time

I have the following script I am using for creating an Radar system. I have recently add code to draw a texture called texture. This has a declaration for it that allows it to rotate and its called angle. I need to know how to cause the angle to change to cause it to spin over time forever.

Here is the code:

 using UnityEngine;
 using System.Collections;
 
 public class Test : MonoBehaviour {
 
 
     public Texture blip;
     public Texture blip2;
     public Texture radarBG;
     public Texture radarFG;
     public Transform centerObject;
     public float mapScale = 0.3f;
     public Vector2 mapCenter;
     public float screenWidth=1024.0f;
     public float screenHeight=768.0f;
     public int mapLocation = 3;
 
     public string tagFilter = "Enemy";
     public string tagFilter2 = "Planet";
     public float maxDist = 200;
     
     public Texture2D texture = null;
     public float angle = 0;
     public Vector2 size = new Vector2(128, 128);
     public Vector2 pos = new Vector2(0, 0);
     Rect rect;
     Vector2 pivot;
 
 
  void Start() 
     {
         UpdateSettings();
     }
     
     
     void UpdateSettings() 
     {
         rect = new Rect(new Rect(screenWidth - radarBG.width, screenHeight - radarBG.height, radarBG.width, radarBG.height));
         pivot = new Vector2(rect.xMin + rect.width * 0.5f, rect.yMin + rect.height * 0.5f);
    }
 
 
 
     public void OnGUI()
     {
         
 
       
         GUI.DrawTexture(new Rect(screenWidth - radarBG.width, screenHeight - radarBG.height, radarBG.width, radarBG.height), radarBG);
           UnityEngine.GUI.DrawTexture(new Rect(screenWidth - radarBG.width, screenHeight - radarBG.height, radarBG.width, radarBG.height), radarBG);
         
           mapCenter = new Vector2(screenWidth-(radarBG.width / 2),screenHeight-(radarBG.height / 2));
           
         if (Application.isEditor) { UpdateSettings(); }
         Matrix4x4 matrixBackup = GUI.matrix;
         GUIUtility.RotateAroundPivot(angle, pivot);
         GUI.DrawTexture(rect, texture);
         GUI.matrix = matrixBackup;
 
       DrawBlipsFor(tagFilter);
       DrawBlipsFor2(tagFilter2);
         
         
 
 
     }
  
     private void DrawBlipsFor(string tagName)
     {
       // Find all game objects with tag 
       GameObject[] gos = GameObject.FindGameObjectsWithTag(tagName);
       // Iterate through them
       foreach (GameObject go in gos)
       {
         drawBlip(go, blip);
       }
     }
      private void DrawBlipsFor2(string tagName)
     {
       // Find all game objects with tag 
       GameObject[] gos = GameObject.FindGameObjectsWithTag(tagName);
       // Iterate through them
       foreach (GameObject go in gos)
       {
         drawBlip(go, blip2);
       }
     }
  
     private void drawBlip(GameObject go, Texture aTexture)
     {
       Vector3 centerPos = centerObject.position;
       Vector3 extPos = go.transform.position;
  
       // first we need to get the distance of the enemy from the player
       float dist = Vector3.Distance(centerPos, extPos);
  
       float dx = centerPos.x - extPos.x; // how far to the side of the player is the enemy?
       float dz = centerPos.z - extPos.z; // how far in front or behind the player is the enemy?
  
       // what's the angle to turn to face the enemy - compensating for the player's turning?
       float deltay = Mathf.Atan2(dx, dz) * Mathf.Rad2Deg - 270 - centerObject.eulerAngles.y;
  
       // just basic trigonometry to find the point x,y (enemy's location) given the angle deltay
       float bX = dist * Mathf.Cos(deltay * Mathf.Deg2Rad);
       float bY = dist * Mathf.Sin(deltay * Mathf.Deg2Rad);
  
       bX = bX * mapScale; // scales down the x-coordinate by half so that the plot stays within our radar
       bY = bY * mapScale; // scales down the y-coordinate by half so that the plot stays within our radar
  
       if (dist <= maxDist)
       {
         // this is the diameter of our largest radar circle
         UnityEngine.GUI.DrawTexture(new Rect(mapCenter.x + bX, mapCenter.y + bY, 10, 10), aTexture);
       }
     }
   }