No abstract

No abstract

A potyvirus, which we call ceratobium mosaic virus, has been detected in about one third of more than 100 plants representing c. 33 orchid genera in two collections in Australia. It was detected using RT-PCR with redundant primers that are Potyviridae-specific and have additional sequences corresponding to either the SP6 or T7 bacteriophage promoters at their 5'-termini. Thus the nucleotide sequence of the resulting PCR fragments, consisting of about 1.7 kb of the 3' portion of the viral genome, could be determined directly. Viral sequences obtained from five infected orchids indicate that they contained different isolates of a single potyvirus species most closely related to the bean common mosaic group of potyviruses, but clearly distinct from all whose virion protein genes have been reported to the international gene sequence databases.

The nucleotide sequence of the thioredoxin gene from Escherichia coli was determined. The structural gene was identified on a cloned 3-kb PvuII fragment by hybridization with a synthetic oligodeoxyribonucleotide corresponding to a part of the amino acid sequence of thioredoxin. Restriction-enzyme fragments were used as templates in the dideoxy sequence method, directly and after subcloning into M13mp8. A segment of 450 nucleotides was determined using both strands, alternatively, without extensive overlaps. The sequence contains the thioredoxin coding region, a potential ribosome-binding site, and a putative promotor region. The predicted amino acid sequence differs by two inversions from the previously given thioredoxin sequence. The revised sequence is presented and the results further show that thioredoxins from E. coli B and K12 are identical.