Abstract
Insect vectors play significant roles in geminivirus spread and evolution in nature. To date little is known about the population dynamics of begomoviruses in their insect vector Bemisia tabaci. In this study we analyzed the genetic variation of tomato yellow leaf curl virus (TYLCV) in its host plant, Solanum lycopersicum, in its transmission vector B. tabaci raised on TYLCV-infected S. lycopersicum plants, and in B. tabaci after being transferred from S. lycopersicum to Gossypium hirsutum. We found that the levels of variability of TYLCV remained stable in S. lycopersicum plants, but increased significantly in both invasive and indigenous species of B. tabaci. We also presented evidence that the elevated mutation frequencies in TYLCV populations from vector whiteflies were caused mainly by mutations that occurred at several distinct sites within the TYLCV genome. Simultaneous introduction of mutations in the hot spots did not affect the ability of TYLCV to be transmitted by B. tabaci, but reduced its pathogenicity in both S. lycopersicum and Nicotiana benthamiana. Our findings provide new information on population variability of TYLCV in its insect vector, extending the knowledge of the influence of insect vector on plant virus population dynamics.
Highlights
Mutations that occur during virus replication are one of the main sources of genetic variation in viruses
Mutations observed in the populations from the Tomato yellow leaf curl virus (TYLCV)-infected tomato plants at various dpi were distributed randomly across the viral genome, with the levels of genetic variation ranging from 2.02 × 10−4 to 3.66 × 10−4 (Fig. 1, Table 1)
The C to T, T to C, A to G transitions, and a T to G transversion were, the main changes in the populations from B. tabaci MED whiteflies collected at 15 d after being transferred to cotton plants (Table 3). These findings indicate that there are major substitution biases in the populations from B. tabaci MED whiteflies fed on cotton plants compared with those obtained from TYLCV-infected tomato plants or from B. tabaci MED whiteflies collected at 12 h acquisition access period (AAP)
Summary
Mutations that occur during virus replication are one of the main sources of genetic variation in viruses. Different steps of the life cycle of RNA viruses, such as vector-mediated transmissions and systemic colonization of new leaves, may impose a bottleneck[6,7,8] These bottlenecks could have profound effects on the maintenance of genetic variation of virus populations, thereby determing the extent to which different random forces drive virus evolution. Tomato yellow leaf curl virus (TYLCV) in the genus Begomovirus of the family Geminiviridae is one of the devastating viruses causing tomato yellow leaf curl disease (TYLCD). It was originally described in the Middle East in the 1960’s, and has spread to tropical, subtropical and temperate regions of the world. Introduction of mutations occurring in the TYLCV progeny obtained from whiteflies reduced the pathogenicity of TYLCV in both tomato and N. benthamiana
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