Sequence diversity of NS(M) movement protein of tospoviruses.

In order to determine the diversity of the movement protein (NS(M)) among tospoviruses, the NSM genes of five distinct tospovirus species occurring in Brazil (Tomato chlorotic spot virus, Groundnut ring spot virus, Chrysanthemum stem necrosis virus, Zucchini lethal chlorosis virus and Iris yellow spot virus) were cloned, sequenced and compared with NS(M) sequences of other available tospoviruses. The 'D-motif', a conserved region present in the majority of '30K superfamily' virus movement proteins, is present in all NSM amino acid sequences available. In addition to the 'D-motif', a conserved phospholipase A2 motif was found. The NSM amino acid sequence comparisons among tospovirus species revealed several conserved regions located in the internal part of the protein and diverse domains mainly located in the amino-terminus. Prediction of secondary structure showed similar patterns among all NS(M) proteins analyzed. Considering the geographical prevalence and phylogenetic analysis of N and NS(M) proteins, tospoviruses were tentatively clustered in 'American' and 'Eurasian' groups. Both phylogenetic trees may reflect the natural evolution of tospovirus species within distinct ecological niches. The sequence information obtained in this work would facilitate functional analysis of NS(M) during the tospovirus infection process.