Sense- and antisense-mediated resistance against Sri Lankan cassava mosaic virus (SLCMV) in Nicotiana benthamiana

Abstract

Sri Lankan cassava mosaic virus (SLCMV) is the principal causal agent of cassava mosaic disease in the Indian subcontinent. To gain resistance against the virus, the coat protein (CP) gene, namely the AV1 of SLCMV-Adivaram isolate, was cloned in either sense or antisense orientation under the Cauliflower mosaic virus 35S promoter, and transgenic Nicotiana benthamiana plants were obtained through Agrobacterium-mediated transformation. A total of eight T1 transgenic lines, four harboring the CP-sense construct and four harboring the CP-antisense construct were challenged with agro-infectious clones of SLCMV DNA-A and DNA-B. Based on symptom exhibition at 20 days post inoculation, 3 out of the 4 CP-sense transgenic lines and all 4 CP-antisense transgenic lines showed a high level of resistance against SLCMV. In addition, a delay in symptom initiation was observed in all the transgenic lines inoculated with a high viral load at agro-dilution 1:625 from an absorbance (A600) of 1. However, the resistance was more prominent at a lower viral load of 1:1000 agro-dilution. The viral titer was lower in the SLCMV-challenged transgenic lines compared to the non-transgenic N. benthamiana plants as confirmed by quantitative PCR and dot blot analysis. Furthermore, small RNA Northern blot analysis revealed lowered amounts of virus-specific small interfering RNAs in the resistant transgenic lines as compared to the non-transgenic plants upon SLCMV infection, which correlates to lower virus titers due to resistance against the virus.

Cassava mosaic disease in South and Southeast Asia: current status and prospects

“…Subsequent to several evaluation trials of MNga-1 (a breeding line from IITA) in the field conditions of India, CTCRI has released a variety named Sree Padmanabha in the state of Tamil Nadu, which showed high-level resistance to ICMV and SLCMV, and has been used in developing resistant clones through intervarietal hybridization (Nair et al, 1998;Unnikrishnan et al, 2002;Abraham et al, 2006;George et al, 2012). In addition, evaluation of the MNga-1 seedling population yielded CMR1 and CMR129 with CMD resistance and high starch content (Unnikrishnan et al, 2011).…”

RNA Interference: A Novel Technology for Virus Disease Management in Crop Plants

“…Similarly, tobacco plants transformed with hpRNA containing CP gene of TSV through the Agrobacterium, mediated transformation exhibited resistance to TSV upon mechanical inoculation and ELISA confirmed the lower level of virus titre in transgenic tobacco lines (Rajamanickam et al, 2015a). Gogoi et al (2019) found that transgenic tobacco plant expressing sense and antisense orientation of CP gene of Sri Lankan cassava mosaic virus (SLCMV) showed resistance to SLCMV. The Northern blot analysis of tobacco line confirmed the expression of virus specific siRNAs, indicated that RNA silencing technology has been adopted in virus resistance.…”

“…In pathogen-derived resistance (PDR), a portion or full viral genome is inserted into a plant; thereafter, it regulates or interferes with vital steps in the life cycle of the pathogen,which led to resistance in plants against virus infection. Diverse viral pathogen-derived genes such as coat protein, movement protein and replicase genes have been effectively utilized to buildout the virus-resistant transformants (Baulcombe, 2002;Senthilraja et al, 2018;Gogoi et al, 2019).…”

Metabolic profiles of Sri Lankan cassava mosaic virus-infected and healthy cassava (Manihot esculenta Crantz) cultivars with tolerance and susceptibility phenotypes

“…Cassava ( Manihot esculenta Crantz) is the third most common plant-based carbohydrate source after rice and maize [ 1 ]. It is used for human consumption, animal feed, and plant-based energy production.…”