The subject invention pertains to novel mutant polynucleotide molecules
that encode enzymes that have increased heat stability. These
polynucleotides, when expressed in plants, result in increased yield in
plants grown under conditions of heat stress. The polynucleotide
molecules of the subject invention encode maize endosperm ADP glucose
pyrophosphorylase (AGP) and soluble starch synthase (SSS) enzyme
activities. Plants and plant tissue bred to contain, or transformed with,
the mutant polynucleotides, and expressing the polypeptides encoded by
the polynucleotides, are also contemplated by the present invention. The
subject invention also concerns methods for isolating polynucleotides and
polypeptides contemplated within the scope of the invention. Methods for
increasing yield in plants grown under conditions of heat stress are also
provided.
