Variants of Peach latent mosaic viroid inducing peach calico: uneven distribution in infected plants and requirements of the insertion containing the pathogenicity determinant.
Previous characterization of Peach latent mosaic viroid (PLMVd) variants from a single peach calico (PC) isolate showed that PC symptoms are induced by variants with a 12-13 nt insertion at a specific position and folding into a hairpin with a U-rich loop. Here, this study was extended to two other PC isolates. PLMVd variants with insertions similar to those reported previously (type 1), predominated in one isolate (PC-P2). The second (PC-P1), in addition to these variants, contained others with insertions in the same position and of the same size, but with the hairpin capped by a GA-rich loop (type 2). When symptomatic and non-symptomatic tissues from both isolates were used to inoculate GF-305 peach seedlings, they reproduced the phenotype of the inoculum source, indicating that variants differing in pathogenicity are unevenly distributed within single plants. Moreover, characterization of the progeny from inoculations with the PC-P1 source showed that variants with insertions of type 1 and 2 were predominant in the symptomatic and non-symptomatic seedlings, respectively, confirming the association between PC and variants with type 1 but not type 2 insertions. Inoculations with dimeric in vitro transcripts from PLMVd variants with type 1, type 2 and with a chimeric insertion showed that the variant with type 2 insertion was latent and established that the U-rich capping loop has a major role in PC, although the adjacent stem may also have some influence. Insertions can be acquired and lost during infection, suggesting that latent variants can evolve into pathogenic variants and vice versa.
Rodio
Maria-Elena
ME
Dipartimento di Protezione delle Piante e Microbiologia Applicata, Università degli Studi and Istituto di Virologia Vegetale del CNR, Sezione di Bari, Via Amendola 165/A, 70126 Bari, Italy.
Delgado
Sonia
S
Instituto de Biología Molecular y Celular de Plantas (UPV-CSIC), Universidad Politécnica de Valencia, 46022 Valencia, Spain.
Flores
Ricardo
R
Instituto de Biología Molecular y Celular de Plantas (UPV-CSIC), Universidad Politécnica de Valencia, 46022 Valencia, Spain.
Serio
Francesco Di
FD
Dipartimento di Protezione delle Piante e Microbiologia Applicata, Università degli Studi and Istituto di Virologia Vegetale del CNR, Sezione di Bari, Via Amendola 165/A, 70126 Bari, Italy.
D014644:Genetic Variation; D008969:Molecular Sequence Data; D009029:Mosaic Viruses / Q000235:genetics / Q000472:pathogenicity*; D010935:Plant Diseases / Q000821:virology*; D018515:Plant Leaves / Q000821:virology; D027861:Prunus / Q000821:virology*; D014772:Viroids / Q000145:classification / Q000235:genetics / Q000472:pathogenicity*; D017735:Virus Latency / Q000235:genetics