Performance Of Transgenic Maize Overexpressing ABP9 Under Drought Stress In The Field

Drought is a major environmental factor that severely limits plant productivity in China, often causing extensive economic loss to agriculture. As global climate change progresses, agricultural production worldwide faces serious threats from frequent extreme weather conditions. Developments of plant varieties that can alleviate the negative impacts of environmental stresses to maintain yield stability are essential to sustain and increase agriculture production. Maize(Zea mays L.) is a major crop in China and worldwide. Its production and yield stability are greatly affected by drought stress. Improving drought tolerance in maize has become one of the top priorities for maize enhancement programs in both private and public sectors. Previously we cloned a transcription factor ABP9 from maize that its overexpression in Arabidopsis confers tolerance to mutiple abiotic stresses including drought. To examine its function in maize, transgenic maize plants overexpressing ABP9 were generated. In this research, we evaluated the performance of the transgenic maize plants expressing each of the four constructs of ABP9 under the control of different promoters, namely Pabp9-ABP9.1, Pubi-ABP9.1, Pubi-ABP9.2 and Pubi-ABP9-3xFLAG under both drought at vegetative and reproductive stages and well watered conditions in the field in 2015 and identified several transgenic events showing high level of tolerance to drought stress. During drought stress imposed at vegetative stage, transgenic events 201, 206, 212 and 214 of Pabp9-ABP9.1, 611, 612, 616 and 617 of Pubi-ABP9.1, 707, 714 and 717 of Pubi-ABP9.2, as well as 809 and 815 of Pubi-ABP9-3xFLAG exibited higher chlorophyll fluorescence, increased NDVI, reduced ASI, increased kernel number/ear, 100 kernel weight and average ear grain yield comparing to non-transgenic plants, while similar phenotypes were also observed with transgenic events 201, 202, 204 and 214 of Pabp9-ABP9.1, 617 and 618 of Pubi-ABP9.1, 707 and 714 of Pubi-ABP9.2, as well as 808 and 817 of Pubi-ABP9-3xFLAG when drought was applied at reproductive stage. Under well-watered conditions, transgenic events 201, 210, 212 and 214 of Pabp9-ABP9.1, 611, 617, 612 and 618 of Pubi-ABP9.1, 702, 707, 714 and 717 of Pubi-ABP9.2, and 803, 807, 808 and 817 of Pubi-ABP9-3xFLAG also showed improved traits such as elevated chlorophyll fluorescence, better NDVI, reduced ASI, increased kernel number/ear, 100 kernel weight and average ear grain yield as compared to non-transgenic plants. Collectively, the transgenic maize events identified in this study are valuable resources not only for further disection of the molecular mechanism of ABP9 action in maize, but also for development of biotech products with enhanced drought tolerance.