Biological and molecular analysis of the pathogenic variant C3 of potato spindle tuber viroid (PSTVd) evolved during adaptation to chamomile (Matricaria chamomilla).

Viroid-caused pathogenesis is a specific process dependent on viroid and host genotype(s), and may involve viroid-specific small RNAs (vsRNAs). We describe a new PSTVd variant C3, evolved through sequence adaptation to the host chamomile (Matricaria chamomilla) after biolistic inoculation with PSTVd-KF440-2, which causes extraordinary strong ('lethal') symptoms. The deletion of a single adenine A in the oligoA stretch of the pathogenicity (P) domain appears characteristic of PSTVd-C3.

Elimination of hop latent viroid upon developmental activation of pollen nucleases.

Hop latent viroid (HLVd) is not transmissible through hop generative tissues and seeds. Here we describe the process of HLVd elimination during development of hop pollen. HLVd propagates in uninucleate hop pollen, but is eliminated at stages following first pollen mitosis during pollen vacuolization and maturation.

Accumulation of viroid-specific small RNAs and increase in nucleolytic activities linked to viroid-caused pathogenesis.

Strong viroid-caused pathogenesis was achieved in tomato cv. Rutgers by biolistic transfer of severe or lethal potato spindle tuber viroid (PSTVd) strains, while other tomato genotypes (e.g.

Sequence analysis of a "true" chalcone synthase (chs_H1) oligofamily from hop (Humulus lupulus L.) and PAP1 activation of chs_H1 in heterologous systems.

Screening of a cDNA library of the hop cv. Osvald's 72 and genomic cloning were used to isolate members of an oligofamily of chs_H1 genes that codetermine the biosynthesis of prenylated chalcones known to be valuable medicinal compounds present in hop (Humulus lupulus L.).

Analysis of thermal stress-mediated PSTVd variation and biolistic inoculation of progeny of viroid "thermomutants" to tomato and Brassica species.

Thermal stress of PSTVd-infected Nicotiana benthamiana led to appearance of a broad PSTVd sequence distribution, where most of mutations accumulated in the left half of the viroid's secondary structure including the "pathogenicity" domain. A similar effect had been reported for hop latent viroid [Virology 287 (2001) 349]. The pool of viroid "thermomutants" progenies was transcribed into cDNA and used for biolistic inoculation of Raphanus sativa, where the PSTVd infection was detectable by reverse transcription and polymerase chain reaction (RT-PCR).