Cloning and Function of MeABF1 in Cassava

Objective The gene of transcription factor ABF1 from Manihot esculenta Crantz (MeABF1) was cloned, and its prokaryotic expression and disease resistance-related function analyzed.

Method Coding sequence (CDS) of MeABF1 was amplified from the M. esculenta cultivar, 'South China 124' ('SC124'). MeABF1-pET32a fusion expression vector was constructed and transformed into DE3 competent cells for protein induction. Expression of the gene was determined by SDS-PAGE and western blotting. Cassava leaves were sprayed with a solution of purified MeABF1 protein and tested for burst of reactive oxygen species (ROS), expression of pathogenesis-related gene (PR), and disease resistance to Xanthomonas axonopodis pv. manihotis (Xam).

Result The CDS sequence of MeABF1 was 1491 bp long. The MeABF1-Myc fusion protein with increasing band intensity over time was detected after 1 mmol·L⁻¹ isopropyl β-D-thiogalactoside (IPTG) induction at 37 ℃ for 1 h. The peak ROS burst in the treated leaves was 3-fold of control, and the MePR1 and MePR2 expressions upregulated 3.5-fold and 1.75-fold, respectively. A 2 d treatment significantly enhanced the disease resistance to Xam of the cassava leaves. The bacterial counts and lesion area on the leaves 6 d post inoculation (dpi) were significantly reduced with improved phenotypic outcomes over control.

Conclusion MeABF1-pET32a was successfully expressed in cassava leaves with the induction by 1 mmol·L⁻¹ IPTG at 37 °C. The foliar MeABF1 application significantly enhanced the resistance of the leaves to Xam infection with burst of ROS and heightened PR expression.