Peach latent mosaic viroid (PLMVd) displays an unusual pathogenic behavior. While consistent with its name most isolates do not incite foliar symptoms, some incite peach mosaic (PM) or an extreme albinism (peach calico, PC). PLMVd variants inducing PC have a characteristic insertion of 12-13 nt and accumulate in symptomatic leaf sectors but not in the adjacent green sectors. Based on these two findings and on additional experimental data (including deep sequencing of viroid-derived small RNAs) we recently proposed that PC could be mediated by RNA silencing. Extending similar analyses to PM first entails identification of the molecular determinant of PM, a question posing serious difficulties because it is not associated with a specific insertion. Moreover, in contrast with PC which is a well-defined syndrome, PM varies very much in intensity and distribution. After examining different PLMVd-PM isolates over the years, we focused on a few of them. This paper reports results obtained with one of such isolates, recovered from the peach cultivar O'Henry grown in Aragón (Spain), expressing an intense mosaic in leaf sectors intermingled with asymptomatic sectors. Previously, RNAs extracted from both sectors of the same leaves were used to generate by RT-PCR full-length PLMVd-cDNAs that were cloned and sequenced. Their multiple alignment revealed specific changes correlating with symptoms. Two clones (Ab4 and Ab7), differing in a single substitution, were used in order to produce dimeric head-to-tail inserts and then in vitro transcripts which were mechanically inoculated onto GF-305 peach seedlings. Intriguingly, while Ab4 incited strong chlorotic symptoms in most leaves, Ab7 only incited mild lesions, providing a first insight of a PLMVd nucleotide directly involved in PM. Moreover, RT-PCR amplification, cloning and sequencing showed that the differential nucleotide substitution was preserved in most of the clones from the symptomatic sectors, but no in those from the surrounding green sectors.
Peach latent mosaic viroid: further insights on a determinant associated with peach mosaic.
Navarro B;Di Serio F;
2012
Abstract
Peach latent mosaic viroid (PLMVd) displays an unusual pathogenic behavior. While consistent with its name most isolates do not incite foliar symptoms, some incite peach mosaic (PM) or an extreme albinism (peach calico, PC). PLMVd variants inducing PC have a characteristic insertion of 12-13 nt and accumulate in symptomatic leaf sectors but not in the adjacent green sectors. Based on these two findings and on additional experimental data (including deep sequencing of viroid-derived small RNAs) we recently proposed that PC could be mediated by RNA silencing. Extending similar analyses to PM first entails identification of the molecular determinant of PM, a question posing serious difficulties because it is not associated with a specific insertion. Moreover, in contrast with PC which is a well-defined syndrome, PM varies very much in intensity and distribution. After examining different PLMVd-PM isolates over the years, we focused on a few of them. This paper reports results obtained with one of such isolates, recovered from the peach cultivar O'Henry grown in Aragón (Spain), expressing an intense mosaic in leaf sectors intermingled with asymptomatic sectors. Previously, RNAs extracted from both sectors of the same leaves were used to generate by RT-PCR full-length PLMVd-cDNAs that were cloned and sequenced. Their multiple alignment revealed specific changes correlating with symptoms. Two clones (Ab4 and Ab7), differing in a single substitution, were used in order to produce dimeric head-to-tail inserts and then in vitro transcripts which were mechanically inoculated onto GF-305 peach seedlings. Intriguingly, while Ab4 incited strong chlorotic symptoms in most leaves, Ab7 only incited mild lesions, providing a first insight of a PLMVd nucleotide directly involved in PM. Moreover, RT-PCR amplification, cloning and sequencing showed that the differential nucleotide substitution was preserved in most of the clones from the symptomatic sectors, but no in those from the surrounding green sectors.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
