Overexpression of Glutathione reductase in cotton does not alter emergence rates under temperature stress
Cotton (Gossypium hirsutum L.) seedlings are considered to be sensitive to temperature stress. The exposure of plants to high and low temperatures can result in the production of reactive oxygen species that contribute to diminished plant performance. Plants have mechanisms that metabolize oxidants into less harmful chemicals, and enhancement of antioxidant metabolism has been shown to be beneficial to plants exposed to acute oxidative stresses. Transgenic overexpression of glutathione reductase (GR) in cotton could result in faster seedling emergence at nonoptimal temperatures. Transgenic GR and 5 nontransgenic cotton lines were planted at four dates in the field in Lubbock, TX, and in constant temperature growth boxes. The temperatures in the field were typical for the cotton planting period in the region, and in growth boxes ranged from 15 to 45°C. Emergence rates were determined for all lines, and the activity of GR and the levels of malondialdehyde in the cotyledons were monitored to verify altered enzyme activity and to detect differences in oxidative damage, respectively. Enhancement of GR activity did not improve emergence or reduce oxidative damage. It is concluded that GR activity did not limit emergence.