If the agency defaults in the payment of principal or interest on any issue of notes or bonds after the same shall become due, whether at maturity or upon call for redemption, and such default continues for a period of 30 days, or if the agency fails or refuses to comply with the provisions of this chapter, or defaults in any agreement made with the holders of any issue of notes or bonds, the holders of 25 percent in aggregate principal amount of the notes or bonds of such issue then outstanding may appoint a trustee to represent the holders of such notes or bonds for the purposes set forth in section 462A.17, unless the notes or bonds are issued under an indenture made and entered into by the agency with a designated trustee.