Journal of Microbiology

Research Support, Non-U.S. Gov'ts

Generation of Infectious Transcripts from Korean Strain and Mild Mottle Strain of Potato Virus X: Sun Hee Choi , Ki Hyun Ryu; J. Microbiol. 2008;46(5):502-507. Published online October 31, 2008; DOI: https://doi.org/10.1007/s12275-008-0078-2

Abstract: Full-length cDNAs of two different strains of Potato virus X (PVX-Kr and PVX-Mo) have been directly amplified by long template reverse transcription polymerase chain reaction (RT-PCR) using the 5’-end primer containing a SP6 or T7 RNA promoter sequence and the virus-specific 3’-end primer, and then constructed in plasmid vectors. Capped in vitro transcripts from cloned full-length cDNAs as well as those RTPCR amplicons proved to be infectious systemically on tobacco plants. Symptom expression on tobacco plants from PVX-Mo transcripts was faster and severer than that from PVX-Kr. In replication stability test of transcripts derived from PVX clones, progeny viruses showed stable replication according to sequencing through passages. This highly infectious transcript system from the full-length cDNA clones for PVX can be useful for recombinant molecules for functional analysis of viral proteins in plant-virus interaction study as well as for expression of foreign protein in planta.

Factors Influencing Preferential Utilization of RNA Polymerase Containing Sigma-38 in Stationary-Phase Gene Expression in Escherichia coli: Eun Young Kim , Min-Sang Shin , Joon Haeng Rhee , Hyon E. Choy; J. Microbiol. 2004;42(2):103-110.; DOI: https://doi.org/2037 [pii]

Abstract: In order to understand the molecular basis of selective expression of stationary-phase genes by RNA polymerase containing [sigma]^38 (E[sigma]^38) in Escherichia coli, we examined transcription from the stationaryphase promoters, katEP, bolAP, hdeABP, csgBAP, and mcbP, in vivo and in vitro. Although these promoters are preferentially recognized in vivo by E[sigma]^38, they are transcribed in vitro by both E[sigma]^38 and E[sigma]^70 containing the major exponential [sigma], [sigma]^70. In the presence of high concentrations of glutamate salts, however, only E[sigma]^38 was able to efficiently transcribe from these promoters, which supports the concept that the promoter selectivity of [sigma]^38 -containing RNA polymerase is observed only under specific reaction conditions. The examination of 6S RNA, which is encoded by the ssr1 gene in vivo, showed that it reduced E[sigma]^70 activity during the stationary phase, but this reduction of activity did not result in the elevation of E[sigma]^38 activity. Thus, the preferential expression of stationary-phase genes by E[sigma]^38 is unlikely the consequence of selective inhibition of E[sigma]^70 by 6S RNA.

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