Origin, Structure, and Regulation of Argk, Encoding the Phaseolotoxin-Resistant Ornithine Carbamoyltransferase in Pseudomonas-Syringae Pv Phaseolicola, and Functional Expression of Argk in Transgenic Tobacco (Journal article)

Hatziloukas, E./ Panopoulos, N. J.

Pseudomonas syringae pv. phaseolicola produces the tripeptide N(delta)(N'-sulfo-diaminophosphinyl)-ornithyl-alanyl-homoarginine (phaseolotoxin), which functions as a chlorosis-inducing toxin in the bean halo blight disease by inhibiting ornithine carbamoyltransferase (OCT). The bacterium possesses duplicate OCT genes, one of which, argK, encodes a toxin-resistant enzyme (ROCT) and imparts resistance to phaseolotoxin. We sequenced the argK gene from strain NPS3121, defined its promoter region, analyzed its regulation, and characterized its transcripts. The gene probably originated from another organism, since it is very distantly related to the argF gene encoding the housekeeping toxin-sensitive OCT and has low G+C content compared with the bacterial genome as a whole and with other protein-coding genes from P. syringae pv. phaseolicola. Optimized alignments of 13 OCT sequences allowed us to define key residues that may be responsible for toxin resistance and to identify a distinct prokaryotic amino acid signature in ROCT, which argues for a prokaryotic origin of argK. An in-frame fusion of the argK coding region with the chloroplast transit peptide segment of the pea rbcS gene was introduced in Nicotiana tabacum by Agrobacterium-mediated transformation. The presence of an ROCT activity in transgenic plants was demonstrated by in vitro and in vivo assays. Some plants were toxin resistant, suggesting that pathogen-derived resistance to the toxin should be feasible in the pathogen's host.
Institution and School/Department of submitter: Πανεπιστήμιο Ιωαννίνων. Σχολή Επιστημών και Τεχνολογιών. Τμήμα Βιολογικών Εφαρμογών και Τεχνολογιών
Keywords: coli aspartate transcarbamoylase,phosphate binding-site,pisum-sativum-l,escherichia-coli,nucleotide-sequence,saccharomyces-cerevisiae,carbamoyl phosphate,molecular evolution,gene,DNA
URI: http://olympias.lib.uoi.gr/jspui/handle/123456789/7817
ISSN: 0021-9193
Link: <Go to ISI>://A1992JN26400017
Appears in Collections:Άρθρα σε επιστημονικά περιοδικά ( Ανοικτά)

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