AtCBF4 gene, derived from Arabidopsis thaliana, is a homolog of the DREB1
transcription factors. It has an important role in the plant's drought
stress response. There are four members of the CBF family, which are
responsible for the plants' response to abiotic stresses. The first three
genes, CBF1, CBF2 and CBF3, are essential for low temperature responses
while CBF4 is vital for drought responses. Previous studies have proved that
transgenic Arabidopsis over-expressing this CBF4 were more tolerant to water
deficit, suggesting its role in the plant response to drought. Researchers
believe that this effect of the overexpression in Arabidopsis is also
applicable to maize.

The study reports the characterization of transgenic maize (inbred line
Mo17) expressing AtCBF4 from Arabidopsis. Morphological and physiological
traits related to drought tolerance, such as relative water content (RWC),
were measured. Results showed that the expression of AtCBF4 in maize
significantly enhanced its drought tolerance. Under dehydration stress,
AtCBF4 transgenic plants showed lower cell membrane damage and higher RWC.
The transgenic lines also had better growth and development, greater biomass
and a significant increase in grain yield compared to wild types.

The transgenic lines kept significantly higher germination index and drought
tolerance index under PEG condition. These results strongly indicate that
expression of AtCBF4 could increase drought tolerances in maize.

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