The attorney general shall prosecute and defend all actions in the supreme court, in which the state shall be interested, or a party; he may, in his discretion, designate one of the assistant attorneys general to be known as the solicitor general, who, under his direction, shall have charge of such causes in the supreme court and shall perform such other duties as may be assigned to him; and the attorney general shall also, when requested by the governor, or either branch of the legislature, and may, when in his own judgment the interests of the state require it, intervene in and appear for the people of this state in any other court or tribunal, in any cause or matter, civil or criminal, in which the people of this state may be a party or interested.