Expression of AtGA2ox1 enhances drought tolerance in maize

Drought is a major limiting factor to maize (Zea mays L.) yield. Plant hormones, including gibberellins (GAs), play important roles in plant response to drought stress. In previous studies, significant reductions in GAs levels have been reported under drought stress. In maize, GA content is correlated to drought tolerance, but the molecular mechanism remains unclear. In the present study, AtG2ox1, a member of the GA2ox family with a clear function, was used to create GA deficiency maize. The transgenic maize had a higher chlorophyll content and faster growth rate, when compared to the wild type (WT) plants, under drought stress in a greenhouse. The physiological and biochemical test results revealed that transgenic maize had decreased levels of GA1 and malondialdehyde (MDA), and increased content of proline and soluble sugars, and antioxidant enzyme activities, when compared to the WT. Furthermore, the transcriptomic analysis revealed that some differentially expressed genes involved in transcription factors correlated to drought stress and abiotic stress responses, and that signaling was enriched. All these results reveal the possible molecular mechanism of GA regulation in drought tolerance, in which the overexpression of AtGA2ox1 altered the expression of multiple genes correlated to the internal antioxidant system and maintenance of cell osmotic potential. The present study demonstrates that the overexpression of AtGA2ox1 could control GA content and improve drought tolerance in transgenic maize. Furthermore, this strategy represents a novel approach to address drought tolerance in maize breeding.