Table 2: Approaches to increase ascorbic acid content or redox state through increasing DHAR expression.

SpeciesTissueSubcellular location Gene sourceFold increase in AscFold increase in Asc redox stateConsequence of increasing DHAR expression Reference

TobaccoLeavesCytosolWheat2.2 to 3.92 to 3Increased GSH content and redox state; increased ozone tolerance; reduced ROS; reduced photoinhibition; embryo twinning [11, 141, 146, 162, 178, 181]
TobaccoLeavesCytosolArabidopsis1.9 to 2.12.4 to 2.6Enhanced tolerance to ozone, drought, and salt[182]
TobaccoLeavesCytosolArabidopsis1.31.6Enhanced tolerance to aluminum[183]
TobaccoLeavesChloroplastHumanNo change2Increased GR activity; lower GSH redox state; enhanced tolerance to low temperature and oxidative stress[179, 180]
Tobacco LeavesChloroplastRice1.62.4 to 3Increased GSH content; decreased GSH redox state; enhanced tolerance to salt and cold stress[184]
Potato LeavesCytosolSesame1.5Not reported1.6-fold increase in Asc in tubers as well using 35S promoter[185]
Potato LeavesCytosolPotato1.61.61.2-fold increase in Asc in tubers as well using 35S promoter[186]
Potato LeavesChloroplastPotato1.4 to 1.51.4 to 1.5No increase in Asc in tubers[186]
Arabidopsis LeavesCytosolArabidopsis2 to 4.253 to 16Increased GSH content and redox state; enhanced tolerance to high-light and high-temperature stress[187]
Arabidopsis LeavesCytosolRice1.1 to 1.40.9 to 1.1Enhanced tolerance to salt stress[188]
Maize LeavesCytosolWheat1.81.3 to 1.4Increased GSH content and redox state[11]
Tomato FruitCytosolTomato1.6Not reportedNo increase in foliar Asc content[189]
Potato TubersCytosolSesame1.1 to 1.3Not reportedNo change in foliar Asc content using the tuber-specific patatin promoter[185]
Maize KernelsCytosolWheat1.91 to 4Improved nutritive value of maize grain; increased GSH content and redox state[11]
Maize KernelsCytosolWheat6Not reportedImproved nutritive value of maize grain[13]