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Abstract
Cotton leafroll dwarf virus (CLRDV, genus: Polerovirus, family: Solemoviridae), is a serious pathogen in cotton production transmitted by the cotton/melon aphid, Aphis gossypii Glover, in a circulative, and non-propagative manner. Among fourteen plant species tested, only hibiscus, okra and prickly sida, were identified as the alternate hosts of CLRDV and aphid in this study. Host plant responses to virus infection vary significantly between different plant species. It is unclear how gene expression profiles differ following aphid feeding and aphid-mediated transmission of a polerovirus between hosts. Gene expression patterns following CLRDV infection in cotton and alternate hosts were assessed. Gene expression profiles were also examined to tease out the differences between aphid feeding and aphid-mediated inoculation of CLRDV in four hosts. The defense genes associated with salicylic acid, jasmonic acid, pathogen-related proteins, heat shock proteins, transcription factors and membrane transporters were differentially expressed between hosts in CLRDV-infected plants. These categories were also differentially expressed upon aphid feeding alone. Acquisition of polerovirus by aphid induced associated gene expression. The transcriptomic analysis of viruliferous aphids that acquired CLRDV from different plant species identified only four common DEGs among viruliferous aphids. The unique DEGs were associated with virus infection, signal transduction, immune systems, and fitness in aphids. These induced changes were not consistent across four alternate hosts. The association of these DEGs with aphid behavior, and fitness of aphids on virus-infected and non-infected cotton and hibiscus plants were evaluated by conducting dual-choice assay, no-choice assay and fitness assay. In contrast to generally accepted preference of non-viruliferous aphids to infected plants and vice-versa in enamo, polero, and sobemovirus pathosystems, both viruliferous and non-viruliferous aphids preferred non-infected cotton and hibiscus plants. Overall, the assessment of tripartite interactions between CLRDV, aphid vector and host species were conducted at both macro and micro levels, revealing that host species behave differentially to virus-infection and vector-feeding. This may impact aphid behavior and fitness even when the same virus isolate is acquired from the host species of same family. These results indicate that differences in host susceptibility to the virus and/or the vector could differentially influence host-virus, and host-vector interactions.