ZmNHL2 enhances drought tolerance by regulating the expression of stress-responsive genes and ABA signaling pathway in maize

Late embryogenesis abundant (LEA) protein plays an important role in plant response to abiotic stress and growth and development. Research has found that LEA protein plays an important role in plant response to drought stress. Although LEA can enhance plant drought resistance, its specific mechanism of action is not yet clear. To elucidate the potential mechanism of LEA protein in drought resistance, a drought-responsive gene designated ZmNHL2 was identified. Bioinformatics analysis showed that the protein encoded by ZmNHL2 belongs to the LEA-2 protein family. ZmNHL2 contains stress response cis-regulatory elements and ABRE response elements and has positive responses to drought, high temperature, salt stress, and exogenous ABA treatment. Transgenic Arabidopsis and maize plants constitutively overexpressing ZmNHL2 were generated for functional analysis of ZmNHL2. The Arabidopsis Col-0 and the maize B104 wild-type plants showed severe wilting and yellowing of the leaves in response to drought stress induction, whereas the ZmNHL2-overexpression lines showed upright leaves and less wilting and yellowing. Moreover, the relative water content (RWC), and the activities of superoxide dismutase (SOD) and peroxidase (POD) in the ZmNHL2-overexpression transgenic Arabidopsis and maize plants were higher than that of the WT plants, indicating that the overexpression of ZmNHL2 enhances maize tolerance to drought stress. RT-qPCR showed that ZmNHL2-overexpression transgenic plants exhibited higher expression levels of the drought-responsive genes ZmPOD1 and ZmDREB2A, and the ABA-related genes ZmNCED and ZmABF2 under drought-stressed conditions. Our results provide new insights into the regulatory functions and mechanisms of ZmNHL2 in promoting drought tolerance in maize.