The present invention concerns a method for increasing plant yield in plants grown under non-stress growth conditions relative to yield in corresponding wild type plants grown under comparable conditions, the method comprising preferentially increasing activity in the cytosol of a plant cell of a type I DnaJ-like polypeptide or a homologue thereof. One such method comprises introducing and/or expressing in a plant, plant part or plant cell a type I DnaJ-like nucleic acid or variant thereof. The invention also relates to transgenic plants grown under non-stress conditions having introduced and/or expressed therein a type I DnaJ-like nucleic acid or variant thereof, which plants have increased plant yield relative to corresponding wild type plants grown under comparable conditions. The present invention also concerns constructs useful in the methods of the invention.