Localization of abutilon mosaic virus (AbMV) DNA within leaf tissue by in situ hybridization

Abutilon mosaic virus (AbMV) is a whitefly-transmitted geminivirus with a a bipartite genome. Using in situ hybridization AbMV DNA was detected exclusively in the phloem of infected Abutilon sellovianum leaves and intracellularly predominant in the nuclei. No AbMV DNA was found in cells from palisade and spongy parenchyma, the tissues which show the predominant cytopathological effects. A hypothesis is discussed to account for the finding that, while AbMV accumulates in the phloem, symptoms are observed in other tissues. Shoot tips were analyzed by in situ hybridization to determine the earliest stage of leaf development in which AbMV is detectable. We found the first hybridization signals in the sixth to seventh leaf of the shoot tip, whereas we could not detect any viral DNA in younger leaves and meristems. These results are discussed with reference to the relation of AbMV multiplication to the cell cycle.