Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 13, 2006
Publication Date: June 7, 2006
Citation: Burrows, M.E., Benson, E., Smith, D., Caillaud, M., Gildow, F., Gray, S.M. 2006. The genetic regulation of luteovirus and polerovirus transmission in the aphid schizaphis graminum. Phytopathology. 96:828-837.
Interpretive Summary: This work investigates the genetic mechanisms that regulate plant virus transmission by insect vectors. We have studied the progeny of a sexual cross between two populations of an aphid species; one population is capable of transmitting virus, while the other is unable to transmit virus. First and second generation progeny differ in their ability to transmit two related plant viruses that cause barley yellow dwarf disease in cereal crops. Analysis of the findings indicates there is one major gene or group of tightly linked genes which control virus transmission phenotype, but other aphid genes may modify the phenotype. Further analysis of the parent and the progeny that are unable to transmit virus indicate that there are multiple barriers to virus movement in the aphid and that each of the barriers can be genetically separated. The parent aphid has multiple distinct barriers to virus transmission, whereas some of the progeny have only a subset of the barriers that are found in the parent. These progeny will be very useful in identifying the genes and proteins involved in virus transmission. An understanding of the exact mechanisms of virus transmission may lead to the identification of new targets for novel strategies to disrupt the transmission of viruses and decrease virus disease incidence.
In order to develop tools to investigate the insect genes and proteins involved in the circulative, nonpropagative transmission process of luteoviruses, we have made F1 and F2 crosses between a Barley yellow dwarf virus (BYDV) vector and a nonvector clone of the aphid Schizaphis graminum. Segregation of the transmission phenotype for BYDV - SGV and Cereal yellow dwarf virus - RPV was observed in both F1 and F2 generations, indicating the parents are heterozygous for genes involved in transmission. The ability to transmit both viruses was correlated, however individual aphid clones differed in their ability to transmit each virus. This suggests major genes regulate the transmission of both RPV and SGV, but minor genes can affect the transmission of each virus independently. Purified RPV was injected into the hemocoel of inefficient vector clones to determine the active transmission barrier(s). Whereas the salivary gland and hindgut were active barriers in the parent Sg-SC and most of the hybrids tested, other hybrids were identified with single barriers. Real time RT-PCR was used to quantify the acquisition and retention of RNA by vector and nonvector aphids. Both retained viral RNA for extended periods of time, indicating virus is not degraded in the aphid.