Effective delivery of a nematode‐repellent peptide using a root‐cap‐specific promoter

The potential of the MDK4‐20 promoter of Arabidopsis thaliana to direct effective transgenic expression of a secreted nematode‐repellent peptide was investigated. Its expression pattern was studied in both transgenic Arabidopsis and Solanum tuberosum (potato) plants. It directed root‐specific β‐glucuronidase expression in both species that was chiefly localized to cells of the root cap. Use of the fluorescent timer protein dsRED‐E5 established that the MDK4‐20 promoter remains active for longer than the commonly used constitutive promoter CaMV35S in separated potato root border cells. Transgenic Arabidopsis lines that expressed the nematode‐repellent peptide under the control of either AtMDK4‐20 or CaMV35S reduced the establishment of the beet cyst nematode Heterodera schachtii. The best line using the AtMDK4‐20 promoter displayed a level of resistance >80%, comparable to that of lines using the CaMV35S promoter. In transgenic potato plants, 94.9 ± 0.8% resistance to the potato cyst nematode Globodera pallida was achieved using the AtMDK4‐20 promoter, compared with 34.4 ± 8.4% resistance displayed by a line expressing the repellent peptide from the CaMV35S promoter. These results establish the potential of the AtMDK4‐20 promoter to limit expression of a repellent peptide whilst maintaining or even improving the efficacy of the cyst‐nematode defence.