Genome organization of mycoviruses 18-09-24.pdf

Mycovirus classification

1. REFLECTION OF 5 QUESTION OF FUNGAL
VIROLOGY (5 MIN DISCUSSION)

2. GENOME ORGANIZATION
OF MYCOVIRUSES
DrMuhammad Faraz Bhatti

3. CLASS LEARNING OBJECTIVES
▪Students will be acquainted with the viral classification
▪Description of different mycoviralgenomes as per classification

4. Class engagement activity
The code36 93 04 3expiresin 14 days

5. BALTIMORE CLASSIFICATION
David Baltimore Nobel
prize 1975
Classification in 1971
Caltech Archives
ID:1.2.001-6
https://www.ncbi.nlm.nih.gov/books/NBK559437/figure/F3/
▪https://www.youtube
.com/watch?v=cKQ9
iolhux4

6. CLASSIFICATION OF FUNGAL VIRUSES
(adapted from Van de Sande et al., [2010]).

7. 7
Adapted from Kotta-Loizou I and Coutts RHA (2017). Front. Microbiol. 8:1699.
Classification of Mycoviruses

11. 7

12. Partitiviridae (dsRNA)
•No. of segments – 2
•Size range – 1.4-2.4 kbp
e.g., Rosellinia necatrixpartitivirus 6 (RnPV6)
ORF 1 (RdRp, 756 aa)
ORF 2 (CP, 729 aa)
5’
5’ 3’
3’
dsRNA 1
dsRNA 2
180 23502462
1 85 22742499
(A) n
(A) n

13. Totiviridae(dsRNA)
•Monosegmented, bicistronic
•Size range – 4.6-7.0 kbp
•e.g., Rosellinia necatrix victorivirus 1
(RnVV1)
ORF2(CP)
ORF1(RDRP)

14. Chrysoviridae(dsRNA)
•3-7 segments
•Size range 1.2-3.6 kbp
•Colletotrichum gloeosprioides chrysovirus 1 (CgCV1)
ORF 1(RdRp ,1080aa)
ORF2 (CP, 900aa)
Hypothetical protein (823 aa)
5’
5’
5’
3’
3’
3’
1
1
1
72
67
72
33973338
28692774
26302538
dsRNA 1
dsRNA 2
dsRNA 3

15. Megabirnaviridae(dsRNA)
•Two genome segment
•Size 7.2, 8.9 Kb
•e.g., Rosellinia necatrix megabirnavirus 2 (RnMBV2)
ORF 1 (CP) ORF 2 (RdRp)
ORF 3
dsRNA 1
dsRNA 2
5’
5’
3’
3’
A CP-RdRP fusion protein is translated
from a bicistronic transcript of dsRNA1
and encapsidated in virus particles

16. Quadriviridae(dsRNA)
•four monocistronic genome segments
•3.7–4.9 kbp in length.
•Accommodates a single species to date, Rosellinia necatrix quadrivirus1(RnQV1)
•dsRNA2 and dsRNA4 (capsid protein, CP)
while dsRNA3 encodes the replicase (RNA-
dependent RNA polymerase, RdRP). dsRNA1
encodes a non-structural protein of unknown
function
•All the genomic segments except for dsRNA3
have (CAA)
nrepeats, which are presumably
translational enhancers
Double lines indicate genomic dsRNAs; boxes indicate open reading frames on the positive-sense
strands which begin and end at the nucleotide positions indicated.
.

17. Reoviridae(dsRNA)
Figure. Genome organization of Mycoreovirus 1(MyRV1)
•Mycoreovirus genome segments
are monocistronic with 5 caps on
their positive strands.
•MyRV1 and-2 have 11 genome
segments (S1–S11) whereas
MyRV3 has 12 segments ,
•Size range: 0.7–4.1kbp in length.
lipidation modification

18. Endornaviridae(dsRNA/ssRNA)
•Do not form true virions;
•The linear dsRNA replicons,14–17kbp long, are found in cytoplasmic vesicles in infected
plants,fungi and oomycetes.
•Each characterized genome encodes a single long polypeptide that includes aa sequences
typical of viral RNA helicases, UDP glucosyl transferases (Involved in Immunity) and RdRps
A conservedRNA-directed RNA polymerase (RdRP)
domain located in the C-terminal region of the
polyprotein is a common feature among all
endornaviruses.
phytoreo_S7 domain
cysteine-rich regionmethyl transferase
viral helicase superfamily

19. Alphaflexiviridae(+RNA)
•Botrytis virus X,which infects the phytopathogenic fungus Botrytis cinerea is the
only known member of genus Botrexvirus in this family.
•Its genome consists of a single linear molecule of +RNA, 7.0kbinlength
excluding the 3’ poly(A) tail and encompassing five ORFs.
•ORF1 encodes a large protein with methyltransferase(cappingenzyme),
helicase, and RdRp motifs, and ORF3 encodes the CP (the only structural
protein).
•The functions of the other predicted translation products(ORF2,-4,and-5) are
unknown
ORF1 encodes the 158 kDa replication-associated (Rep) protein, ORF3 encodes the 44 kDa capsid
protein (CP) and the functions of the other predicted proteins (ORF2, 30 kDa; ORF4, 14 kDa and ORF5,
14 kDa) are unknown

20. Barnaviridae(+RNA)
•Mushroom bacilliform virus(MBV),is the prototype of genus Barnavirus, the only known genus in
family Barnaviridae.
•Virions contain a single linear molecule of a positive sense ssRNA, 4.0 kb in size, and a single
major CP of 21.9 kDa.
•Comprises four major and three minor ORFs.
•The deduced aa sequence of ORF2 contains putative serine protease motifs related to
chymotrypsin.
•ORF3 encodes a putative RdRp and ORF4 encodes the CP.
•The polypeptides potentially encoded by ORFs 1, 5, 6 and 7 show no sequence similarity to
known polypeptides

21. Gammaflexiviridae(+RNA)
•Botrytis virus F is the prototype of genus Mycoflexivirus in this family.
•Its genome consists of a single linear moleculeof +RNA
•6.8 kb in length excluding the 3’-poly(A) tail and encompassing two major
ORFs.
•ORF1 encodes a large protein(153kDa) with methyltransferase and helicase
motifs and terminating with a UGA stop codon

22. Hypoviridae(+RNA)
Figure. Genome organization of Cryphonectria hypovirus 4 (CHV-4), which is 9.1 kb.
Arrows represent known or suspected sites of autoproteolysis.
•Cryphonectria hypoviruses 1to4 (CHV1to-4) are currently grouped in sole
genus Hypovirus within this family.
•The hypovirus genomes were originally thought to be dsRNA but are now
considered to be +RNA
• 9–13 kb in length excluding the 3’ poly(A) tail and encompassing two
minimally overlapping ORFs in CHV1 and-2 but only one ORF in CHV3 and -4.

23. Narnaviridae(+RNA)
•Members of this family contain the simplest genomes of any
autonomous RNA virus.
•Each a single linear molecule of +RNA
• 2.3–3.6 kb in length
•Encompassing a single ORF that encodes the RdRp

24. Mycomononegaviridae(-RNA)
•Sclerotinia sclerotiorum negative-stranded RNA virus 1 (SsNSRV1) is the
prototype of this proposed family.
• Its genome consists of a single linear molecule of RNA, 10kb in length
and encompassing six consecutive, non-overlapping ORFs.
•The largest ORF(ORF5,L) encodes largeprotein withRdRp and
methyltransferase motifs

25. Genomoviridae(ssDNA)
Figure 1. Genome map of SsHADV-1. Genes encoding the replication-initiation protein (Rep)
and capsid protein (CP) are shown with blue and red arrows, respectively. The position of the
nonanucleotide (Nona) important for rolling-circle replication is also indicated.
accommodate the only ssDNA virus known to infect fungi, a circular molecule
encapsidated in isometric virions.