HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Google Scholar Articles by Teixeira, D. C. Articles by Bové, J. M. PubMed PubMed Citation Articles by Teixeira, D. C. Articles by Bové, J. M. Agricola Articles by Teixeira, D. C. Articles by Bové, J. M.

The tufB–secE–nusG–rplKAJL–rpoB gene cluster of the liberibacters: sequence comparisons, phylogeny and speciation

¹ Fundecitrus, Araraquara, SP, CEP 14807-040, Brazil
² Université de Bordeaux 2, UMR 1090, F-33883 Villenave d'Ornon, BP 81, France
³ INRA, UMR 1090, F-33883 Villenave d'Ornon, BP 81, France

Correspondence
S. Eveillard
Sandrine.Eveillard{at}bordeaux.inra.fr

The rplKAJL–rpoBC operon or β operon is a classic bacterial gene cluster, which codes for proteins K, A, J and L of the large ribosomal subunit, as well as proteins B (β subunit) and C (β' subunit) of RNA polymerase. In the early 1990s, the operon was obtained as a 2.6 kbp DNA fragment (In-2.6) by random cloning of DNA from periwinkle plants infected with the Poona (India) strain of the huanglongbing agent, later named ‘Candidatus (Ca.) Liberibacter asiaticus’. DNA from periwinkle plants infected with the Nelspruit strain (South Africa) of ‘Ca. L. africanus’ was amplified with a primer pair designed from In-2.6 and yielded, after cloning and sequencing, a 1.7 kbp DNA fragment (AS-1.7) of the β operon of ‘Ca. L. africanus’. The β operon of the American liberibacter, as well as the three upstream genes (tufB, secE, nusG), have now also been obtained by the technique of chromosome walking and extend over 4673 bp, comprising the following genes: tufB, secE, nusG, rplK, rplA, rplJ, rplL and rpoB. The sequence of the β operon was also determined for a Brazilian strain of ‘Ca. L. asiaticus’, from nusG to rpoB (3025 bp), and was found to share 99 % identity with the corresponding β operon sequences of an Indian and a Japanese strain. Finally, the β operon sequence of ‘Ca. L. africanus’ was extended from 1673 bp (rplA to rpoB) to 3013 bp (nusG to rpoB), making it possible to compare the β operon sequences of the African, Asian and American liberibacters over a length of 3000 bp, from nusG to rpoB. While ‘Ca. L. africanus’ and ‘Ca. L. asiaticus’ shared 81.2 % sequence identity, the percentage for ‘Ca. L. americanus’ and ‘Ca. L. africanus’ was only 72.2 %, and identity for ‘Ca. L. americanus’ and ‘Ca. L. asiaticus’ was only 71.4 %. The 3000 bp nusG–rpoB sequence was also used to construct a phylogenetic tree, and this tree was found to be identical to the known 16S rRNA gene sequence-based tree. These results confirm earlier findings that ‘Ca. L. americanus’ is a distinct liberibacter, more distantly related to ‘Ca. L. africanus’ and ‘Ca. L. asiaticus’ than ‘Ca. L. africanus’ is to ‘Ca. L. asiaticus’. The dates of speciation have also been estimated.

The GenBank/EMBL/DDBJ accession numbers for the β operon sequences of ‘Ca. L. americanus’ São Paulo and ‘Ca. L. africanus’ Brazil are respectively EF122254 and EU078703.