The development of genetically modified maize for abiotic stress tolerance

Drought is one of the most serious abiotic stresses affecting crops in Africa. Our group has been addressing the problem using genes obtained from the resurrection plant, Xerophyta viscosa. This South African indigenous monocot, which grows in cracks in rocks in the Drakensberg range of mountains in KwaZulu-Natal province, can tolerate losses of up to 95% relative water content. Upon rehydration, it can “resurrect” within 72 h. It can also tolerate high and low temperatures ranging from 40 °C to below freezing. We have used genes from this plant to transform maize and the model plant, Arabidopsis thaliana, to determine which could be used to confer drought resistance. XvSAP1 codes for a signalling membrane hydrophobic protein with little similarity to any protein in gene banks. It was transformed into A. thaliana and constitutive expression led to higher growth rates during osmotic, high salinity and high temperature stress compared with control plants. Non-transgenic plants had shorter roots, leaf expansion was inhibited and leaves were more chlorotic than those of the transgenic plants. This gene has been transformed into maize and results of exposure to abiotic stresses will be presented. XvAld1 codes for an aldose reductase that converts glucose to sorbitol. Transgenic A. thaliana were more tolerant to osmotic stress, high temperatures and salinity than non-transgenic controls. XvPrx2 encodes a type II peroxiredoxin which is induced in X. viscosa by dehydration, low temperature and ABA. Transgenic maize plants have been made carrying this gene and results of exposure to abiotic stresses will be presented. XvPer1 encodes a 1-Cys peroxiredoxin which is induced in X. viscosa by dehydration, heat, high light intensity and salinity. In initial experiments, transgenic maize expressing this gene showed some tolerance to high light intensity but this was not maintained. Other X. viscosa genes under study include XvERD15 (early-responsive to dehydration), XvINO1 coding for Myo-inositol 1-phosphate synthase, XvGolS coding for galactinol synthase, XvVHA-c″1 encoding a vacuolar H+ATPase subunit c″. The status of their studies will be presented. Future work will include the transformation of maize with XvALD, the generation of more maize plants expressing XvSAP1 and XvPrx2. These will be driven by a stress inducible promoter