Review Article
BEGOMOVIRUSES AND
BETASATELLITES ASSOCIATED WITH CLCuD
*YAQOOB S, FATIMA
N, KHAN S, ALI Q, HAFEEZ MM, MALIK A
Institute of
Molecular Biology and Biotechnology, University of Lahore, Lahore, Pakistan
Corresponding author email: s.yaqoob10@gmail.com
(Received
5th January 2020; Accepted 4th April 2020)
Abstract: Begomoviruses are one of the major types of plant
viruses. They are transmitted by whitefly and cause many diseases. The CLCuD is the most damaging disease of cotton. It is the
vector of begomoviruses, namely as monpartite or bipartite begomoviruses.
Bipartite begomoviruses are consisted of A and B DNA molecuales. Monopatite consist of
single genome. It is mainly linked with alphasatellites
and betasatellites. Alphasatellites
can replicate by using replication protein and not called as true satellites. Betasatellites are called as true satellites as they are
linked with alphasatellites. Mainly cause tomato
yellow leaf curl disease. Begomoviruses are different
from other plant viruses as the basis of RNA genomes. DNA beta satellite is
involves in suppressing the expressions of genes in plants. It has a major role
in preventing RNA silencing by encoding proteins that binds with DNA and target
the nucleus of cell. Affected plants show various symptoms such as leaf
curling, enations etc. that cause loss in cotton
field by preventing the growth. With the help of PCR, 1.4 kb fragments of DNA have
been amplified from DNA template. For cloning the whole begomoviruses
genome, a simple method of cloning has been widely used. Cloning is usually done
by using the bacteriophage DNA polymerase. The betasatellites have shown association with CLCuD.
Keywords:
Begomoviruses, whitefly, betasatellites, alphasatellites,
cotton, tomato, leaf curl disease
Introduction
Cotton is considered as cash crop of
Pakistan. Cotton plant is used as raw material in textile industry and has a
very soft and hairy natural fiber which grows within boll like structures which
carried the seeds of cotton. Major countries which are producing cotton are
India, China, Brazil, Pakistan, Australia, Uzbekistan, Turkey and USA.
Pakistanis fourth largest cotton producing country with 8,800,1000
(480lb) cotton bales, contributing 2% to country GDP and up to 8.2% value in
agriculture added. The total estimated area of Pakistan under cotton
cultivation was 2.96 million hectares. Pakistan comprises over number of miles,
finishing units, oil expellers and more than 1000 ginneries (Abbas
et al., 2013; Abbas et al., 2016b; Puspito et al., 2015). Punjab
province is producing 80%-85% of cotton whereas Sindh
is producing 15-20% of cotton. In Punjab cotton growing areas are Southern
Punjab which are called ‘cotton belt’ mainly in the areas of Central Punjab and
Sindh. Punjab areas mainly include Sahiwal, Faislabad, Toba Tak Singh and Jhang. Sindh areas include Sukkur, Feroze, Hyderabad, Shahdadpur and
Sakrand.
Diseases
of cotton
In Pakistan yield of cotton is reducing
day by day for the last many years due to low quality seed, poor farming
practices, rains at time of sowing, increase in temperature at flowering stage,
delay the wheat harvest time, attack of insect pests and one of the most common
one is cotton leaf curl disease. Mostly the chewing
insects included the American, pink, spotted bollworms and army chew the leaves
of cotton plants which are thick and juicy. Sucking types of insects are
aphids, jassids, thrips, mealybug and whitefly they feed by sucking the other plants
(Abbas
et al., 2016a; Puspito et al., 2015; Rehman et al., 2017). Mealybug and whitefly are the two insects which are the
major threat for cotton crop in present time. Many other diseases of cotton crop
such as bacterial disease known as crown gall, fungal disease are verticillium wilt, root knot (nematode) and viral disease
known as anthocyanosis, leaf motile and leaf crumple (Husnain,
2016; Rehman et al., 2017).
Cotton leaf curl disease
Begomoviruses are major
viruses that cause cotton leaf curl disease (Figure 1). This disease is mainly
caused by whitefly. It is the major biotic constraint to cotton production. The
leaf curling, enations, darkening, vein thickening
and swollen veins, young leaves become yellowish, bushy appearance, leathery
texture, wilted look of the leaves, margins of the leaves inward and outward
and stunning of plants are the symptoms of cotton leaf curl virus disease (Airapetian
et al., 2004; Dimmock et al., 2008; Rehman et al., 2017).
Fig 1: cotton leaf curl disease in Indian
subcontinent (https://alchetron.com/Cotton-leaf-curl-virus)
Viruses
The virus, also known as poison, word virus
is a Latin. Virus is an infectious agent which could move and replicate only
within a host cells and has a core of nucleic acid which is either RNA or DNA
encapsulated into coat of protein or within a coat of lipid layers. They are
inactivated functionally outside the host body and are not able to store free
energy or even captured energy. They are not genuine microorganisms usually
regarded as pathogens or parasites (Desnues
et al., 2008). Dimmock statement about viruses is, “viruses occur
universally, most viruses can exist with their hosts. Although viruses are well
known for causing disease but can only be detected indirectly” (Dimmock
et al., 2008). Martinus Beijerinck in 1898, was
discovered the first virus known as Tobacco
mosaic virus (TMV). Viruses are of different shapes. Some are helical and
some are icosahedra in shape. The size of the viruses varies from 12nm-2000 nm.
Miniviruses have the largest genome; the genome size
of the miniviruses is 1.2Mb whereas, ciroviruses and geminiviruses
have smallest genome; the genome size of these viruses is 1739-2819 (Calisher
and Van Regenmortel, 2009a). Various diseases are caused by
viruses in human, plants and animals. In plants, viruses spread from one host
to another by using a vector or carrier. i.e. horizontal gene transfer is
considered as important tool to transform gene along with a best source for
genetic variations among species (Bernard
et al., 2010).
Begomovirus
Begomoviruses have largest
genus from the family Geminiviridae which has above 100 different species. The name of begomovirus
has been derived from BGMV or Bean golden mosaic virus (Liu
et al., 1997). They affect dicotyledonous
plants both in new and old world and are transmitted by Whitefly. Symptoms of begomoviruses infection are vein thickening, leaf curling, enations and yellowing of leaves. They affect crop plants including
tomato, cassava, beans, cotton and squash. Due to resistance point of view we
study deeply this virus. Begomoviruses
are classified as two groups the monopartite and
bipartite based on its genomic size. 2.6- 2.8 kb size of each genomic component
(Briddon
and Markham, 2000).
Bipartite
begomoviruses
Genome of bipartite begomoviruses
is consisted of DNA A and B both. The DNA A encoded replication which is associated
with protein, coat protein, transcriptional activator protein, the replication
enhancing protein and encoded protein that has been involved in movement of
virus, the RNA suppressor for splicing and determinant for pathogenicity.
DNA-B encodes movement protein and nuclear shutter protein (Van Regenmortel, 2007).
Monopartite begomoviruses
Monopartite begomoviruses have a role as a progenitor molecule. It has
a single genome component of DNA A. Monopartite begomoviruses only reported in old world. Have same
components like bipartite begomoviruses, contain six
ORFs, four are the complementary sense and two are virion
sense.
Becurtoviruses
Becurtoviruses genome consists
of three ORFs (V1, V2, and V3) in the virion-sense strand
and two complementary – sense ORFs (C1, C2). The V1, V2, V3 encode coat
protein, movement protein and protein involved in regulating SSDNA. The C1, C2
ORFs have the same position in genome like Mastrevirus.
Becurtoviruses have no C3 and C4 ORFs. Rep ORFs
contain intron sequence. It has TAAGATTCC
mononucleotide sequence at the v-ori.
Capulavirus
Replication associated proteins from spliced
transcript are encoded by two complementary senses (C1, C2). Canonical ring
circle replication motifs the ATPase motifs Walker A,
B, C contained by replication protein of Capulavirus and
in amino acid sequences Rep sequence of geminiviruses
are present. C3 is embedded in C1 ORF.
Grablovirus
Other monopartite geminiviruses ranging
from 2.7 to 3.0 kb but the monopartite genome of 3.2
kb of grapevine red blotch virus is larger than other monopartite
geminiviruses. The genomic organization of this virus
is not similar to that of other geminiviruses. The virion sense and complementary sense ORFs have no
homologous in members of the other genera in the family.
Eragroviruses
Eragroviruses have very rare organization of genome with a TAAGATTCC
sequence at virion strand origin of replication and
different or unspliced Rep (like Becurtoviruses).
Genome of Eragroviruses is similar with others genome
by showing unique geminiviruses genera. The C2 ORF is
similar with begomovirus, Topocovirus
and CurtovirusTrAP/TrAP-like
genes because it is a positional analog for all of these. Eurasian mastreviruses is similar with V1 ORF which is mainly
encoding the capsid protein of Geminiviruses.
The Eragroviruses Rep is mostly related to those of begomoviruses, Curtoviruses, and Topocovirus.
Cotton
leaf curl disease history
Africa
In 1912, in Nigeria a mycologist first
time report the evidence of cotton leaf curl disease in the native cotton
species like Gossypiumperuvianum
and Gossypiumvitifolium
with the leaf curl and vein thickening symptoms. Farquharson
was first time used the term ‘leaf curl’(Farquharson,
1912). In 1924 this
disease was appear again in irregular intervals in time. This disease was
reported again from Gezira, Sudan and
named as “Stenosis in cotton” in the same year (Lambert,
1924). In 1926,
disease samples which were collected from southern Nigeria and herbarium
specimens collected from Sudan, was examined by Jones and Mason and called it
as a viral disease (Jones
and Mason, 1926). Disease
appeared in epidemic form in Sudan in 1927-28 and affects half of the cotton
crop in Gezira (Kerr
and Bailey, 1934). Many Bemisia sp. and infestation of whitefly were
found to link with leaf curl symptoms development (Hussain
and Al-Jaloud, 1995).
Asia
In Asia, during 1967 CLCuD
was first time reported in Pakistan near the district of Multan (Ryan). Sporadic form
of the disease was reported after 20 years. S-12 is a high yielding cotton
variety but in 1988, serious infection was observed on S-12 at MozaKhokran near district of Multan. Since that time, in
all major cotton growing areas of Pakistan infection was recorded but losses of
disease was remained under control for sometimes. S-12 and CIM-70 are two high
yielding cotton varieties and have high susceptibility. ‘Desi
cotton’ is totally immune to leaf curl disease but the farmers choose ‘American
cotton’ which is highly susceptible. Although incidence of the disease was much
lower in Sindh as compare to Punjab (Stoilov
et al., 1998). In 1992-1997,
at high level loss in the economy of Pakistan due to this disease. By using
methods like conventional breeding and selection methods resistant varieties
were introduced to reduce this disease and then there is increase in economy of
Pakistan by overcome this disease (Abdel-Rahman
et al., 2002). But with the
passage of time the symptoms of the disease were appear to the previous cotton
resistant varieties at the district of Burewala and Vehari in 2001 and covered the whole district at the end of
2002 (Briddon,
2003; Mansoor et al., 2003). Strains of the
cotton leaf curl virus was confirmed
by molecular analysis and grafting (Amiji
et al., 2011).Viruses causing
leaf curl disease is highly present in
the area of Sindh both in central, lower Sindh and cause substantial losses (Amrao
et al., 2010).
Satellites
associated with monopartite begomoviruses
Satellites act
as sub viral agents known as nucleic acid molecules that depend upon helper
virus for their replication. They have no nucleotide sequence which is similar
to helper virus genome (Fauquet
et al., 2008). Satellite
viruses and virus associated satellites have a very clear difference. Virus
satellites depend upon helper virus for their purpose. Satellite virus encodes
for their encapsulation by themselves. In 1969, first virus satellite was
identified (Zhou
et al., 2003) due to the leaf
curl disease of cotton. It is a monopartite begomoviruses have both associated satellites; Alphasatellite and Betasatellite.
Beta satellite is surely associated with this disease and alpha satellite is
associated with helper virus (Ciriello
et al., 2015; Cordts et al., 2011; Drmanac et al., 2010). Estimate 10
species of cotton leaf curl virus
have been reported in Pakistan till now.
Alphasatellite
They are also known as true satellites
because they can replicate themselves by encoding a replication protein. The alphasatellite genome size is almost similar to beta
satellite genome. It has a only one Rep gene that is encoded by miniviruses (Claxton
et al., 2001; Cordts et al., 2011; Hamilton et al.,
1989).
Betasatellite
It is a monopartite
begomoviruses have single genomic component and
infectious for the host (Essen
et al., 2002). They are
circular molecule of ssDNA and depend upon helper
virus for replication. Length of the beta satellite is 1350 nt
(Amrao
et al., 2010; Briddon and Stanley,
2006). Genome of the
beta satellite has single ORF in complementary sense, a satellite conserved
region and adenine rich region. It has 150-200 nucleotides in a region known as
satellite conserved region.
Begomoviruses
and Betasatellites
In Pakistan and India cotton leaf curl
disease causes various loss of production and damage the cotton crop due to
this cotton production reduced (Srirajaskanthan and Preedy, 2011). The ssDNA plant viruses are the main cause of CLCuD (Claxton
et al., 2001; Mansoor et al., 2003). This family is
classified into nine genera. These are Begomoviruses,
Grablovirus, Becurtoviruses,
Capulavirus, Curtovirus, Mastrevirus, Eragroviruses, Grablovirus and Turncurtovirus (Varma
et al., 2011). The largest
genus is in Begomovirus family Geminiviridae
and it is contains of 320 species (Calisher
and Van Regenmortel, 2009b; Zhou
et al., 2004). Begomovirusesare transmitted by whitefly (Bisaro
et al., 1982). Begomoviruses disease symptoms are leaf curling, small vein
thickening, large vein thickening, small leaf like enations
under leaf and growth stunting that cause overall loss in crop production. Begomoviruses are classified into 2 main group; Old World
and New World (Desnues
et al., 2008; Essen et al., 2002; Ndunguru et al.,
2005). Begomoviruses are either Bipartite or monopartite
on the basis arrangements of genome. DNA satellites molecules are alphasatellites, betasatellites
and new one is deltasatellites. Betasatellites
are symptoms modulating DNA satellites associated with monopartite
begomoviruses in old world. Some betasatellites
are associated from malvaceos host from one group and
some associated from second group non-malvaceous
host. In 1990, the changes that have been occurred in begomoviruses
are studied and also study the cotton leaf curl disease in Pakistan. The
discovery of cotton leaf curl Multan virus is less extense.
A large amount of difference is present in the cotton leaf curl strains of
Punjab and Sindh area. Betasatellite
is associated with begomoviruses which is reported in
a weed and that weed shows yellowish of vein (Hillocks
et al., 2002; Jenkin et al., 2003; Saunders et al.,
2013). Viral
components that cause infection to the host plant were completed after this
discovery. The components which are responsible for the production of disease has
been reported many times (Kerr
and Bailey, 1934; Kitaura et al., 1996; Klug et al., 2008; Saunders et al.,
2008). The clones of
beta satellites are phenotypically spreaded in the areas of Punjab and Sindh.
All betasatellites are recombinant. Therefore, a
differentiation in A-rich and SCR which are originated from two provinces (Briddon
et al., 2010; Gutierrez et al.,
2004; Hull and Davies,
1992).
CLCuMB has more
ability of transreplication than other malvaceous and non-malvaceousbetasatellite.
Mutations are found in beta-satellite. Mutations are distributed randomly they
are not conserved. Amino acid sequences are requiring for the comparison of beta-satellites.
Symptoms of leaf curl virus disease are based on the expression of the protein
that is encoded on beta-satellite. In tobacco the amplification of molecules
can be determined which is used as a host for the study of plant virus. All
type of plant tissues are responded by both biotic and abiotic
stresses. In Asia and Africa, begomoviruses are the
major problem for the crop plants. In tobacco and Arabidopsis thaliana the
method of begomoviruses host interactions are
determined. Interactions of geminiviruses with other
plants and responses of Arabidopsis are studied. Many research articles are
available (Matthews,
1979; Qin et al., 2004; Stoilov et al., 1998). The Nicotana species has also a role in geminiviruses
study. The geminiviruses used as plant virus
interactions. By using N-benthamiana and N-tabacum many strategies against geminiviruses
has studied in-vitro. This information will help us to study or determine
various differences occur in begomovirus betasatellite complex in association with CLCuD. SiRNA is required for
silencing the CLCuMB Band we can increase its level
by studying amplicon-based RNAi.
There is a need for changing gene construction method in cotton for success and
cotton complex begomoviruses is taken under the
observation in accordance with the field conditions and it is a big challenge.
Many whitefly proteins have been identified recently, which changes the begomovirus transmission may be increase or decrease. Some
proteins present in mid-gut and most of them bind the CP (Turnage
et al., 2002; Van Regenmortel, 2007; Varma et al., 2011). Once the begomoviruses are ingested, it emphasizes tissues and
further mobilized for the control of virus overflow that may be harmful to
insects. A gene is identified recently that gene encode knottin
(knot-1) acts as regulator of virus amounts in B.tabaci. During the virus
circulation in the insect body this gene help in restraining the amount of
TYLCU particles linked with B. tabaci. Q biotypes are recently published by the
sequences of different genome (Hussain
and Al-Jaloud, 1995; Roberts and Stanley,
1994; Srirajaskanthan and
Preedy, 2011). B. tabaci
vector help to increase the knowledge of relationships between B. tabaci
vector intruders and may help to find additional gene that balanced a life
between begomoviruses and begomoviruses
their Whitefly host.
Future challenge
1.
Use
extensive agriculture practices.
2.
High
yielding varieties are introduced.
3.
Use
new host pesticides for increase in the production of whitefly. So whitefly is
appear on new host cause increase in the number of this disease and some of
them become economically important.
Conclusion
Viruses that
affect our plants like begomoviruses have role in
agriculture production. Diseases which are caused by plants viruses are
important because they affect our productivity ratio, security of food.
Therefore, we have knowledge to control the virus in order to prevent diseases
in plants. Recently many experiments are done on plants to prevent virus
infection. To control the effect of virus the whole plant is selected for
molecular characterization. Universal primers are used for cloning purposes. At
the end, the whole sequence was observed to check the similarities and
dissimilarities of CLCuV from other plant viruses
Conflict
of interest
The authors declared the absence of any
conflict of interest.
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