Exchange of Three Amino Acids in the Coat Protein Results in Efficient Whitefly Transmission of a Nontransmissible Abutilon Mosaic Virus Isolate

Abstract

Geminiviruses are transmitted in a circulative manner by whiteflies, leafhoppers, or treehoppers. The whitefly species Bemisia tabaci (Genn.) is the vector for members of the genus Begomovirus. The closely related bipartite Central American begomoviruses Abutilon mosaic virus (AbMV), Sida golden mosaic virus originating from Costa Rica (SiGMV-CR), and Sida golden mosaic virus originating from Honduras (SiGMV-Hoyv) were used to study transmission by their insect vector. The AbMV isolate is defective in transmission, whereas the two Sida-infecting viruses are readily transmitted by B. tabaci. These three viruses are able to form pseudorecombinant viruses by exchange of genomic components. The pseudorecombinant virus SiGMV-Hoyv A/AbMV B was transmissible, whereas the reciprocal pseudorecombinant virus AbMV A/SiGMV-Hoyv B was not transmitted, indicating that DNA B is not involved in the transmission defect. However, the uptake of the pseudorecombinant virus AbMV A/SiGMV-Hoyv B was much better than AbMV itself, indicating that DNA B or DNA B gene products enhance uptake of viral DNA. Exchange of AbMV coat protein with that of SiGMV-CR resulted in a transmissible chimeric AbMV. Mutagenesis of the AbMV coat protein showed that the exchange of two amino acids, at positions 124 and 149, was sufficient to obtain a whitefly-transmissible AbMV mutant. However, when amino acid 174 was altered in addition to amino acids 124 and 149 AbMV was readily transmitted by B. tabaci. From this we conclude that it is not a concise motif, such as the amino acid triplet, aspartate-alanine-glycine (DAG), involved in aphid transmission of potyviruses, that determines transmissibility of begomoviruses by B. tabaci. Instead it is the composition of the coat protein domain from amino acid 123 to 149, as a minimal transmission domain, with the contribution of amino acids 149 to 174 for efficient transmission.

Virion Stability Is Important for the Circulative Transmission of Tomato Yellow Leaf Curl Sardinia Virus by Bemisia tabaci , but Virion Access to Salivary Glands Does Not Guarantee Transmissibility

“…1A). The relevance of this region in transmission has been confirmed for Watermelon chlorotic stunt virus (41) and Abutilon mosaic virus (AbMV) (38).…”

Mutational Analysis of Effectors Encoded by Monopartite Begomoviruses and Their Satellites

“…The CP of the monopartite begomoviruses facilitates the transfer of infecting viral DNA into the host cell nucleus and is essential for systemic virus movement [5,46,50,104]. The CP also determines the vector specificity [10,32,33] and protects the viral ssDNA from degradation during transmission by the insect vector [3], or mechanical inoculation [24].…”

Early Function of the Abutilon Mosaic Virus AC2 Gene as a Replication Brake

“…During 150 years of vegetative propagation of infected host plants, the virus has been attenuated and has lost its capability of whitefly transmission (35). Although it is still able to induce severe symptoms in test plants such as Malva parviflora, only mild symptoms are observed in the model plant Nicotiana benthamiana (33,36,37).…”