Resistance to African cassava mosaic virus conferred by a mutant of the putative NTP-binding domain of the Rep gene (AC1) in Nicotiana benthamiana

We constructed a mutation in DNA A of African cassava mosaic virus (ACMV) t o alter the putative NTP-binding site in the replication-associated protein gene (AC1). When transgenic Nicotiana benthamiana plants expressing the mu tated AC1 gene were infected with ACMV, the plants exhibited tolerance to i nfection consisting in a delay in symptom appearance and/or the presence of mild symptoms. In addition, the resistant plants accumulated less viral DN A than non-transgenic plants. As judged by northern blot analysis and sympt om development of segregating progeny from different lines, a high level of expression of the mutated AC1 gene is essential for the development of res istance. Issues related to the use of different versions of AC1 for the con trol of ACMV are discussed.