Ex-Enron Asst Treasurer Strikes Plea Deal  HOUSTON (Reuters) - A former Enron Corp.  &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=ENRNQ.PK target=/stocks/quickinfo/fullquote"&gt;ENRNQ.PK&lt;/A&gt;  assistant treasurer pleaded guilty on Tuesday in U.S. District  Court to conspiracy to commit securities fraud for disguising  the company's weak finances before its dramatic collapse.