Disclosed is are gene sequences encoding .gamma.-tocopherol methyltransferases from photosynthetic organisms. The enzyme .gamma.-tocopherol methyltransferase catalyzes the methylation of .gamma.-tocopherol to yield .alpha.-tocopherol, the most bioactive species of tocopherol. .gamma.-tocopherol methyltransferase is believed to be involved in regulating the relative amounts of the various tocopherols present in photosynthetic organisms. By introducing a genetic construct having a .gamma.-tocopherol methyltransferase coding sequence placed under the control of a plant promoter into a plant, transgenic plants can be made having altered .gamma.-tocopherol methyltransferase expression, to effect dramatic changes in the tocopherol profile of the plant. Transgenic plants can be made that have .alpha.-tocopherol as the predominant tocopherol in their seeds and oils.