The invention relates to methods of producing a desired phenotype in a plant by manipulation of gene expression within the plant. The method relates to means to increase expression level of a bHLH subgroup 1b gene expression or activity, wherein a desired phenotype such as increased heat tolerance relative to a wild type control plant following heat stress results in reduced flower abortion and increased yield. Included are plants produced by said methods. The invention also relates to nucleic acid sequences and constructs useful such methods and methods of generating and isolating plants having increased expression of a bHLH subgroup 1b expression or activity.