A single amino acid in the helicase domain of PMMoV-S is responsible for its enhanced accumulation in C. chinense (L3L3) plants at 32 °C

In Capsicum chinense (L3L3) plants a higher accumulation of the tobamovirus Pepper mild mottle virus strain S (PMMoV-S) as compared to the Italian strain PMMoV-I is detected when plants are grown at 32 °C. By using a reverse genetic approach, we have established that a single amino acid at position 898 in the helicase domain of the polymerase protein, outside of the conserved regions of the helicase, is critical for the higher accumulation of PMMoV-S observed. It also is necessary for both increased accumulation of viral RNA of both polarities in pepper protoplasts and enhanced cell-to-cell movement in C. chinense plants. The influence of thermoresistance of PMMoV-S, a P1,2 pathotype, and its prevalence on pepper cultivars over PMMoV-I, a P1,2,3, pathotype, is discussed.

► We have determined the complete nucleotide sequence of the genomic RNA from PMMoV-I.
► Phylogenetic analysis shows that the P1,2,3,4 pathotype has arisen from the P1,2 one.
► A single amino acid substitution is critical for its enhanced accumulation at 32 °C.
► We have examined the biological proccess associated to the enhanced accumulation.
► It is associated to a higher accumulation of viral genomic RNAs of both polarities.