Genetic Engineering of Maize with theArabidopsisDREB1A/CBF3Gene Using Split‐Seed Explants

Abstract

Transformation of maize (Zea maysL.) split‐seed explants from inbred line R23 was performed following particle bombardment with a construct carrying theArabidopsistranscriptional factorCBF3under the control of the inducible promoterrd29Aand the selectable marker hygromycin phosphotransferase. OverexpressingCBF3has been shown to enhance cold, drought, and salt tolerance inArabidopsis, tobacco (Nicotiana tabacumL.), and wheat (Triticum aestivumL.). TheCBF3gene was detected in 18 lines by polymerase chain reaction (PCR), and stable integration of multiple copies ofCBF3was confirmed by Southern blot analysis in three selected lines. Reverse transcription PCR detected expression ofCBF3in the transgenic lines under unstressed conditions despite the use of the stress‐induciblerd29Apromoter. This constitutive expression was associated with growth retardation and sterility in most of the transgenic lines. Transmission of the gene in a Mendelian fashion to T1and T2generations was confirmed in one line by Southern blot analysis. Plants of this line showed stress‐inducible expression of theCBF3gene and hardly detectable expression under unstressed conditions along with significant tolerance to cold, drought, and salinity compared with wild‐type plants. These results demonstrate that stress‐inducible overexpression ofCBF3has the potential to enhance abiotic stress tolerance in corn.