A professional corporation which has only 1 shareholder need have only 1 director, who shall be the shareholder. The 1 shareholder shall also serve as the president of the professional corporation. The other officers of the professional corporation, in such a case, need not be licensed or otherwise legally authorized to render the same professional service within this State, as the 1 shareholder. A professional corporation which has only 2 shareholders need have only 2 directors who shall be such shareholders. The 2 shareholders shall, between them, fill all the offices of the professional corporation.