RNA-interference in rice against Rice tungro bacilliform virus results in its decreased accumulation in inoculated rice plants

Abstract

Rice tungro is a viral disease seriously affecting rice production in South and Southeast Asia. Tungro is caused by the simultaneous infection in rice of Rice tungro bacilliform virus (RTBV), a double-stranded DNA virus and Rice tungro spherical virus (RTSV), a single-stranded RNA virus. To apply the concept of RNA-interference (RNAi) for the control of RTBV infection, transgenic rice plants expressing DNA encoding ORF IV of RTBV, both in sense as well as in anti-sense orientation, resulting in the formation of double-stranded (ds) RNA, were raised. RNA blot analysis of two representative lines indicated specific degradation of the transgene transcripts and the accumulation of small molecular weight RNA, a hallmark for RNA-interference. In the two transgenic lines expressing ds-RNA, different resistance responses were observed against RTBV. In one of the above lines (RTBV-O-Ds1), there was an initial rapid buildup of RTBV levels following inoculation, comparable to that of untransformed controls, followed by a sharp reduction, resulting in approximately 50-fold lower viral titers, whereas the untransformed controls maintained high levels of the virus till 40 days post-inoculation (dpi). In RTBV-O-Ds2, RTBV DNA levels gradually rose from an initial low to almost 60% levels of the control by 40 dpi. Line RTBV-O-Ds1 showed symptoms of tungro similar to the untransformed control lines, whereas line RTBV-O-Ds2 showed extremely mild symptoms.

Transgenic rice plants that overexpress transcription factors RF2a and RF2b are tolerant to rice tungro virus replication and disease

“…Disease-tolerant cultivars have thus far been selected by plant breeders; many such lines rely on resistance to insect transmission (5). Pathogen-derived resistance against RTD was reported as being only partially effective, although recent reports involving an RNAi construct are encouraging (5,9). Nevertheless, because of the limitations of current breeding programs and disease management, RTD remains a serious threat to rice production in regions of South and Southeast Asia.…”

Salinity drives host reaction in Phaseolus vulgaris (common bean) to Macrophomina phaseolina

“…For example, resistance can be expressed at the penetration stage by determining the ability of a fungal pathogen to assimilate enough nutrients to be able to proliferate in the tissues or sporulate or spread. Host resistance can be constitutive or induced, and it has been demonstrated in several plant species that induced resistance can be regulated by different signalling pathways (Tyagi et al 2008). The present study shows that host resistance expression (in terms of disease severity) is also impacted by interactive effects of salinity, at least for common bean.…”

RNA interference: concept to reality in crop improvement

“…There are many other transgenic plants with enhanced defence by RNAi-mediated gene silencing, such as Tomato Yellow Leaf Curl Virus (TYLC)-resistant tomato (Fuentes et al 2006), Rice Tungro Bacilliform Virus (RTBV)-resistant rice (Tyagi et al 2008) and Citrus Tristeza Virus (CTV)-resistant mexican lime (López et al 2010). Schwind et al (2009) have even shown that using hpRNA construct in Solanum lycopersicum (tomato) against Potato Spindle Tuber Viroid (PSTVd) produce PSTVd-resistant tomato plant varieties.…”