A Current Overview of the Papaya meleira virus, an Unusual Plant Virus

Abstract

Papaya meleira virus (PMeV) is the causal agent of papaya sticky disease, which is characterized by a spontaneous exudation of fluid and aqueous latex from the papaya fruit and leaves. The latex oxidizes after atmospheric exposure, resulting in a sticky feature on the fruit from which the name of the disease originates. PMeV is an isometric virus particle with a double-stranded RNA (dsRNA) genome of approximately 12 Kb. Unusual for a plant virus, PMeV particles are localized on and linked to the polymers present in the latex. The ability of the PMeV to inhabit such a hostile environment demonstrates an intriguing interaction of the virus with the papaya. A hypersensitivity response is triggered against PMeV infection, and there is a reduction in the proteolytic activity of papaya latex during sticky disease. In papaya leaf tissues, stress responsive proteins, mostly calreticulin and proteasome-related proteins, are up regulated and proteins related to metabolism are down-regulated. Additionally, PMeV modifies the transcription of several miRNAs involved in the modulation of genes related to the ubiquitin-proteasome system. Until now, no PMeV resistant papaya genotype has been identified and roguing is the only viral control strategy available. However, a single inoculation of papaya plants with PMeV dsRNA delayed the progress of viral infection.

Physical Characteristics of the Leaves and Latex of Papaya Plants Infected with the Papaya meleira Virus

“…The vascular bundles form the midribs and veins of the leaf [ 14 ]. One of the defense mechanisms of C. papaya plants is its latex, which is a hostile environment for pathogens; indeed, PMeV is the only pathogen that is confined to the lactiferous conducts of papaya latex and affects solidification in infected plants [ 4 ]. Therefore, it is important not only to study the latex alterations but also to investigate the vascular bundles where the laticifers are confined.…”

“…When infected by PMeV, papaya plants spontaneously exudate the latex from leaves and fruits. The latex oxidizes during atmospheric exposure, resulting in small necrotic lesions on the edges of young leaves and a sticky substance on the fruits that makes them unacceptable for consumption [ 4 , 5 , 6 ]. Light microscopy studies have been conducted to investigate the changes in papaya tissues infected with PMeV [ 7 ].…”

Presencia de Papaya ringspot virus (PRSV) en arvenses asociadas a Carica papaya en Colima, México

“…Viruses affecting papaya crops cause diseases of economic importance worldwide that pose a serious threaten because they reduce fruit production or even cause the total loss of infested plantations (Navanath et al, 2017). Over 10 viruses affecting papaya have been reported worldwide from which the most important are Papaya leaf distortion mosaic virus (PLDMV), Papaya lethal yellowing virus (PLYV), Papaya mosaic virus (PapMV), Papaya melaira virus (PMeV) and Papaya ringspot virus (PRSV) (Abreu et al, 2015). The latter belongs to the family Potyviridae, genus Potyvirus (Fauquet et al, 2005), it is transmitted by vector aphids in a non-persistent manner, develops symptoms in the form of mosaics, chlorosis, leaf distortion and ring-like spots, and is responsible for crop losses ranging from 50 to 90%, and from 30 to 40% at postharvest (Hernández-Castro et al, 2004;Hernández-Castro et al, 2015).…”

“…(Navanath et al, 2017). Se han reportado más de 10 virus que afectan este cultivo en todo el mundo, entre estos los más importantes son Papaya leaf distortion mosaic virus (PLD-MV), Papaya lethal yellowing virus (PLYV), Papaya mosaic virus (PapMV), Papaya melaira virus (PMeV) y Papaya ringspot virus (PRSV) (Abreu et al, 2015). Este último virus pertenece a la familia Potyviridae y al género Potyvirus (Fauquet et al, 2005), el cual se transmite por áfidos vectores de manera no persistente y genera síntomas de mosaicos, clorosis, distorsión en las hojas y manchas características en forma de anillo en el fruto, ocasionando pérdidas del 50 al 90% del cultivo y 30 al 40% en postcosecha (Hernández-Castro et al, 2004;Hernández-Castro et al, 2015).…”

Thrips Species (Thysanoptera: Thripidae) in Brazilian Papaya (Brassicales: Caricaceae) Orchards as Potential Virus Vectors

“…Worldwide, viruses are the main problem of papaya (Carica papaya L.; Brassicales: Caricaceae) and can limit the production (Presley & Ploetz 2003), and the Tomato spotted wilt virus (TSWV) has caused sporadic outbreaks in Hawaiian papaya orchards and in other parts of the world (Gonsalves & Trujillo 1986;Bautista et al 1995;Silva et al 1997). Several viruses may occur in all papaya-growing regions of the world, including Papaya apical necrosis virus (PANV), Papaya meleira virus (PMeV), Papaya lethal yellowing virus (PLYV), and particularly Papaya ringspot virus (PRSV-P), which are the most distributed papaya viruses worldwide (Ventura et al 2004;Riley et al 2011;Abreu et al 2015). The rouging practices, which consist in eliminating plants with initial symptoms of viruses, are required to reduce infected plants and virus dispersion in the field, and yield loss due to viruses may reach up to 100% in Brazil (Ventura et al 2004.…”