Expression of the oligomerization domain of the replication-associated protein (Rep) of Tomato leaf curl New Delhi virus interferes with DNA accumulation of heterologous geminiviruses

The minimal DNA binding domain of the replication-associated protein (Rep) of Tomato leaf curl New Delhi virus was determined by electrophoretic mobil ity gel shift analysis and co-purification assays. DNA binding activity map s to amino acids 1-160 (Rep-(1-160)) of the Rep protein and overlaps with t he protein oligomerization domain. Transient expression of Rep protein (Rep (1-160)) was found to inhibit homologous viral DNA accumulation by 70-86% i n tobacco protoplasts and in Nicotiana benthamiana plants. The results obta ined showed that expression of N-terminal sequences of Rep protein could ef ficiently interfere with DNA binding and oligomerization activities during virus infection. Surprisingly, this protein reduced accumulation of the Afr ican cassava mosaic virus, Pepper huasteco yellow vein virus and Potato yel low mosaic virus by 22-48%, electrophoretic mobility shift assays and co-pu rification studies showed that Rep-(1-160) did not bind with high affinity in vitro to the corresponding common region sequences of heterologous gemin iviruses. However, Rep-(1-160) formed oligomers with the Rep proteins of th e other geminiviruses. These data suggest that the regulation of virus accu mulation may involve binding of the Rep to target DNA sequences and to the other Rep molecules during virus replication.