Coordinated Action of RTBV and RTSV Proteins Suppress Host RNA Silencing Machinery

Abstract

RNA silencing is as an adaptive immune response in plants that limits the accumulation or spread of invading viruses. Successful virus infection entails countering the RNA silencing machinery for efficient replication and systemic spread in the host. The viruses encode proteins with the ability to suppress or block the host silencing mechanism, resulting in severe pathogenic symptoms and diseases. Tungro is a viral disease caused by a complex of two viruses and it provides an excellent system to understand the host and virus interactions during infection. It is known that Rice tungro bacilliform virus (RTBV) is the major determinant of the disease while Rice tungro spherical virus (RTSV) accentuates the symptoms. This study brings to focus the important role of RTBV ORF-IV in disease manifestation, by acting as both the victim and silencer of the RNA silencing pathway. The ORF-IV is a weak suppressor of the S-PTGS or stable silencing, but its suppression activity is augmented in the presence of specific RTSV proteins. Among these, RTBV ORF-IV and RTSV CP3 proteins interact with each other. This interaction may lead to the suppression of localized silencing as well as the spread of silencing in the host plants. The findings present a probable mechanistic glimpse of the requirement of the two viruses in enhancing tungro disease.

The relationship between vector insect populations, natural enemies, and disease incidence of tungro virus during wet and dry seasons

“…The rice plants around the observation site were vegetative in August. According to Anand (2022), the population density of N. virescens is generally low and only increases when the plant is in its vegetative state. The population of vector insects increases from the immigrant generation to the first generation, then the population density decreases (Otuka et al 2008).…”

“…Moreover, by controlling the insect vector population and utilizing rice varieties to planthoppers and tungro it is possible to control tungro disease. Therefore, planting with tungro virus-resistant varieties and green planthoppers is the most effective method of controlling tungro (Bunawan et al 2014;Kim et al 2019;Anand et al 2022).…”

“…If the tungro virus infects rice, its yield potential will not be achieved; even plants attacked during the early vegetative phase will not yield rice (Banerjee et al 2012). Tungro disease affects all phases of plant development, but symptoms are most pronounced during the vegetative phase (Anand et al 2022). Plants affected by tungro experienced leaf discoloration, stunted, reduced tillers, and delayed flowering accompanied by the presence of vectors of both imago, nymph, and eggs (Kim et al 2019).…”

Exploring the Potential of Oryza sativa derived Candidate miRNAs to Target Rice Tungro Bacilliform Virus (RTBV) Genome

“…The two viruses work in an intricate mutual relationship having RTBV encoding suppression activity for handling localized silencing activity of the host, while RTSV components aid in suppression of viral propagation through cell-to-cell facilitating the spread of viral infection 10 . The interaction between these two viruses within single host plant is very complex leading to further complicating RTD progression and obstruct its management 11 . The virus is equally devastating as it infects both the indica and japonica subspecies of rice widely cultivated across Asia.…”

“…Among diverse rice a icting pathogens, Rice Tungro Bacilliform Virus (RTBV) emerged as a formidable adversary, causing discoloration, stunted growth, less number of tillers, sterile and partly lling grains debilitating tungro disease that poses a serious challenge to rice production worldwide, causing substantial economic losses 5 .…”