Notes on Genus: Tenuivirus

branched filaments

Type member: Rice stripe virus

General Description

The genus Tenuivirus is quite distinctive, having members with thin (3-10 nm diameter) filamentous particles and an ambisense genome strategy. It is named from the Latin tenui, meaning thin or weak. The viruses are transmitted by planthoppers in a persistent manner to hosts in the Gramineae.

Morphology

Virions filamentous and not enveloped (may appear to be spiral, branched or circular), 3-10 nm in diameter. There are four or five different lengths.

Genome

Multi- (4 to 6) partite, single stranded, positive sense RNA. Sizes of segments about 9000, 3400-3600, 2300-2500 and 2000-2200 nucleotides. Maize stripe virus contains a fifth RNA of 1300 nucleotides, while rice grassy stunt virus has six RNAs.

Genus Genomic Organization

The proteins are encoded in an ambisense arrangement. In most members, there appears to be a single protein (replicase) encoded in the negative (complementary) sense on RNA1 and two proteins, one each in the positive and negative sense, on the remaining three RNA segments. At least two members (EHBV and MSpV) have a fifth RNA encoding a single protein in the negative (complementary) sense. The coat protein is encoded in the complementary sense on RNA3. In rice grassy stunt virus, each of the six segments has two proteins, one each in the positive and negative sense and the coat protein is encoded in the complementary sense on RNA5.

Type Member Genomic Organization

The genome products are:

ORF	Segment	Sense	Size	Putative Function
1:  pC1	RNA1	-	337 kDa	Polymerase
2:  p2	RNA2	+	23 kDa	membrane-associated protein
3:  pC2	RNA2	-	94 kDa	membrane glycoprotein
4:  p3	RNA3	+	24 kDa	non-structural (cytoplasmic) protein
5:  pC3	RNA3	-	35 kDa	Coat protein (nucleocapsid)
6:  p4	RNA4	+	20 kDa	Non-capsid "S" protein (virus inclusion body protein)
7:  pC4	RNA4	-	32 kDa	non-structural protein