Unique features of Erwinia chrysanthemi (Dickeya dadantii) RA3B genes involved in the blue indigoidine production.
Erwinia chrysanthemi (Ech) RA3B produces a large amount of blue indigoidine. Using Tn5-induced mutagenesis, three indigoidine-deficient mutants were generated. Followed by library screening, a 5.8kb fragment complemented mutants for indigoidine synthesis was cloned. This fragment contains four complete open-reading frames (ORFs), pecS, pecM, idgA, and idgB, and two partial ORFs, argG, and idgC. These genes are nearly identical to those in strain Ech3937. Primer extension assays demonstrated a clear transcriptional start site prior to idgA, while no promoter preceding idgB and idgC was detected, suggesting that idgA, idgB, and idgC are organized as one transcription unit. In contrast, indAB is separated from indC in Ech3937. Interestingly, an ERIC sequence was present between idgB and idgC in place of the promoter region of the homolog indC, which may contribute to the loss of promoter activity in RA3B. Futhermore, idgB mutant displayed much lighter blue color, while indB mutant appeared white on media. Overexpression of pecS in RA3B resulted in significantly reduced indigoidine production and idgC transcript. Moreover, gel shift and luxAB reporter assays revealed that PecS specifically binds to the sequence preceding idgA and inhibits gene expression, which is consistent with the results observed in Ech3937.
Chu
Mu-Kuei
MK
Department of Biological Science and Technology, Chung Hwa University of Medical Technology, Tainan County, Taiwan.
Lin
Lee-Fong
LF
Twu
Chung-Shing
CS
Lin
Rong-Hwa
RH
Lin
Yuan-Chuen
YC
Hsu
Shih-Tien
ST
Tzeng
Kuo-Ching
KC
Huang
Hsiou-Chen
HC
D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D001483:Base Sequence; D016974:Dickeya chrysanthemi / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D010881:Piperidones / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011485:Protein Binding
D001426:Bacterial Proteins; D010881:Piperidones; C446045:indigoidine