Resistance of transgenic papaya plants to Papaya ringspot virus

Abstract

The coat protein gene isolated from Papaya ringspot virus, Thai isolate, was used to generate transgenic papayas. A binary vector containing the coat protein gene under the control of a 35S promoter, was constructed and transformed into somatic embryos of papaya cultivar Khak Dum by microprojectile bombardment. Eight transgenic lines were identified from 1980 bombarded calli of papaya somatic embryos under kanamycin selection. Integration of the transferred genes into kanamycin resistant papaya calli was verified by PCR amplification of the coat protein gene, GUS assays and Southern blot hybridization. Although the coat protein gene was detected in all transgenic lines, only line G2 was found to be highly resistant to virus. This resistant line showed high degree of rearrangement of the inserted coat protein expression cassette while the coat protein gene itself had a deletion of 166 bp on the 3' end of its sequence. Although the transcription of the coat protein gene was detected in all transgenic lines by RT-PCR, only two transgenic papayas expressed the intact coat protein. Moreover, in the resistant line G2 the amount of the truncated coat protein mRNA was significantly decreased. These results point to an RNA mediated mechanism of coat protein mediated resistance in papaya, probably based on post-transcriptional gene silencing.

Different Approaches to Produce Transgenic Virus B Resistant Chrysanthemum

“…Among transgenic plants transformed by the CVB coat protein gene in the antisense (pBAS vector) and sense orientation (pBSS vector), no lines resistant to infection were found. The efficacy of these approaches to produce the plants resistant to viruses was repeatedly confirmed [14,22]. Most likely, the absence of resistant lines in our experiments was due to an insufficient number of studied lines.…”

The Acute bee paralysis virus–Kashmir bee virus–Israeli acute paralysis virus complex

“…It has been demonstrated repeatedly that transgenic plants carrying a portion of a viral genome (generally the coat protein gene) are often resistant to the virus in question (El-Borollosy et al, 2008;Kertbundit et al, 2007;Pedersen et al, 2007). This effect is generally due to interference by the host-expressed viral RNA (or sometimes the translated proteins) with the replication and translation of the infectious virus (Ratcliff et al, 1997(Ratcliff et al, , 1999.…”

Post-transcriptional gene silencing is involved in resistance of transgenic papayas to papaya ringspot virus

“…The G2 resistant line contained greatest number of bands of all transformed lines. The expression cassette, however, is about 500 bp larger than the expected size despite the fact that the CP within this cassette is 166 bp shorter (Kertbundit et al 2007). This result indicates, that not only separate insertions of duplicated fragments have occurred but also a rearrangement of the transgene itself took place.…”

“…Transgenic papaya (Carica papaya L.) lines G1, G2, T1 -T7 used in this study were previously described (Kertbundit et al 2007). Transformed plants originated from a single somatic embryo were transferred to soil in greenhouse and considered as R0 generation.…”