A plant having improved heat tolerance and/or increased growth is produced by steps of: introducing DNA into a plant cell to produce a transformed plant cell, wherein the DNA is selected from the group consisting of: (a) DNA coding for a protein consisting of the amino acid sequence represented by SEQ ID NO: 2, (b) DNA including the coding region of the nucleotide sequence represented by SEQ ID NO: 1, (c) DNA coding for a protein having an amino acid sequence represented by SEQ ID NO: 2 in which one or a few amino acids are substituted, deleted, inserted, and/or added, and being involved in growth promoting effect and heat tolerance, (d) DNA hybridizing with DNA consisting of the nucleotide sequence represented by SEQ ID NO: 1 under stringent conditions and coding for a protein which is involved in growth promoting effect and heat tolerance, and (e) DNA coding for a protein having an amino acid sequence having 90% or more identity with the amino acid sequence represented by SEQ ID NO: 2 and being involved in growth promoting effects, heat tolerance, drought tolerance and salt tolerance; and regenerating a transformed plant from the transformed plant cell.