The United States generates one-fifth of the world's cotton fiber valued at about four billion dollars annually. Although consumers prefer cotton, man-made fibers are capturing a major share of the textile market while the market share of cotton is shrinking. In order for the market share to increase, cotton fiber quality must be improved. In the past, cotton fiber quality has been improved by classical plant breeding; however, this approach is limited by species incompatibility and available traits. An alternative approach is to introduce foreign genes to confer desired traits into cotton via genetic engineering. Protein-based polymers (PBPs) are available in nature as materials with extraordinary mechanical properties, such as spider webs composed of silk threads tougher than steel and elastin, a rubber like elastic fiber found in human arteries, that typically survives for more than 70 years, undergoing repeated cycles of stretching and relaxation. The PBP made from synthetic genes, containing the sequence Val-Pro-Gly-Val-Gly, typically found in elastin, exhibits elastic moduli that can range from 10⁶-10⁹ dynes/cm² and temperature transition properties that enable water absorption 10 times its own weight. Therefore, introducing this PBP into cotton fiber will increase the fiber strength, water absorption, thermal characteristics and dye binding. In this project, we attempt to genetically engineer cotton fiber with a PBP gene, GVGVP, the sequence derived from human elastin.