Incoming United Nations chief Antonio Guterres on Thursday appointed Nigeria's Environment Minister Amina Mohammed as his deputy secretary-general and Brazilian diplomat Maria Luiza Ribeiro Viotti as chef de cabinet, a UN spokesman said. Before her appointment as environment minister a year ago, Mohammed was outgoing UN Secretary-General Ban Ki-moon's special adviser on post-2015 development planning - a role that culminated last year with the adoption by the General Assembly of sustainable development goals for the next 15 years. Guterres succeeds Ban on Jan. 1.