Submitted to: American Society for Virology Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 5/1/2006
Publication Date: 7/15/2006
Citation: Stenger, D.C., Hein, G.L., Gildow, F.E., French, R.C. 2006. Nested deletion analysis of tritimovirus hc-pro. American Society for Virology Meeting. Interpretive Summary:
Technical Abstract: A series of in frame and nested deletions which progressively removed 5’-proximal sequences of the Wheat streak mosaic virus (WSMV) HC-Pro coding region (1152 nts) was constructed in the context of an infectious clone. Transcripts of mutants with 5’-proximal deletions in HC-Pro of 12 to 720 nts systemically infected wheat and retained autoproteolytic activity in vitro. Boundary sequences flanking the deletions were stable and unaltered by passage through plants for all infectious deletion mutants except HCD12 (lacking HC-Pro codons 3-6) that exhibited strong bias for G to A substitution at nt 1190 in HC-Pro codon 2. In contrast, 5’-proximal deletion of 852 nts of the HC-Pro coding region abolished both infectivity and in vitro proteolytic activity. Inoculation of wheat with deletion mutants also bearing the GUS reporter gene revealed that the 852 nt deletion mutant was unable to establish primary infection foci in inoculated leaves, suggesting that correct processing of the P3 amino-terminus was essential. Surprisingly, a WSMV construct with the HC-Pro coding region completely deleted was infectious to wheat, oats, and corn. This result indicated that HC-Pro was not required for WSMV replication, virion assembly, or systemic movement in plants. However, WSMV HC-Pro was required for transmission by the wheat curl mite (Aceria tosichella Keifer), as the complete deletion mutant was not vector transmissible. Deletion of as few as 24 nts (HC-Pro codons 3-10) also eliminated transmission by the wheat curl mite, revealing a vector transmission domain within the amino-terminal region of WSMV HC-Pro. Collectively, these results indicate that tritimovirus HC-Pro has functional domains for vector transmission and polyprotein processing arranged in a fashion similar to that of potyvirus HC-Pro but, unlike potyvirus HC-Pro, tritimovirus HC-Pro does not appear to perform essential function(s) necessary for pathogenicity.