The head of each principal department is a secretary, who shall be appointed by the Governor with the advice and consent of the Senate. The Governor shall select, on the bases of professional and administrative knowledge and experience, a secretary who has the qualifications required by law. Unless otherwise provided by law, the secretary of a principal department or, with the approval of the Governor, a designee of the secretary shall represent the State and coordinate its participation in an interstate, regional, or other intergovernmental unit that is in the department.