title: Unusual Five Copies and Dual Forms of nrdB in "Candidatus Liberibacter asiaticus": Biological Implications and PCR Detection Application.
abstract: "Candidatus Liberibacter asiaticus" (CLas), a non-culturable α-proteobacterium, is associated with citrus Huanglongbing (HLB, yellow shoot disease) currently threatening citrus production worldwide. Here, the whole genome sequence of CLas strain A4 from Guangdong of China was analyzed. Five copies of nrdB, encoding β-subunit of ribonucleotide reductase (RNR), a critical enzyme involving bacterial proliferation, were found. Three nrdB copies were in long form (nrdBL, 1,059 bp) and two were in short form (nrdBS, 378 bp). nrdBSshared >99% identity to 3' end of nrdBLand had no active site. Sequences of CLas nrdB genes formed a distinct monophyletic lineage among eubacteria. To make use of the high copy number feature, a nrdB-based primer set RNRf/RNRr was designed and evaluated using real-time PCR with 262 HLB samples collected from China and USA. Compared to the current standard primer set HLBas/HLBr derived from the 16S rRNA gene, RNRf/RNRr had Ct value reductions of 1.68 (SYBR Green PCR) and 1.77 (TaqMan PCR), thus increasing the detection sensitivity three-fold. Meanwhile, RNRf/RNRr was more than twice the stability of primer set LJ900f/LJ900r derived from multi-copy prophage. The nrdB-based PCR thereby provides a sensitive and reliable CLas detection with broad application, especially for the early diagnosis of HLB.
authors.affiliation: Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Citrus Huanglongbing Research Laboratory, South China Agricultural University, Guangzhou, Peoples' Republic of China.|San Joaquin Valley Agricultural Sciences Center, United States Department of Agriculture-Agricultural Research Service, Parlier, California, United States of America.
authors.forename: Zheng
authors.initials: Z
authors.lastname: Zheng
authors.affiliation: Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Citrus Huanglongbing Research Laboratory, South China Agricultural University, Guangzhou, Peoples' Republic of China.
authors.forename: Meirong
authors.initials: M
authors.lastname: Xu
authors.affiliation: Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Citrus Huanglongbing Research Laboratory, South China Agricultural University, Guangzhou, Peoples' Republic of China.
authors.forename: Minli
authors.initials: M
authors.lastname: Bao
authors.affiliation: Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Citrus Huanglongbing Research Laboratory, South China Agricultural University, Guangzhou, Peoples' Republic of China.|San Joaquin Valley Agricultural Sciences Center, United States Department of Agriculture-Agricultural Research Service, Parlier, California, United States of America.
authors.forename: Fengnian
authors.initials: F
authors.lastname: Wu
authors.affiliation: San Joaquin Valley Agricultural Sciences Center, United States Department of Agriculture-Agricultural Research Service, Parlier, California, United States of America.
authors.forename: Jianchi
authors.initials: J
authors.lastname: Chen
authors.affiliation: Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Citrus Huanglongbing Research Laboratory, South China Agricultural University, Guangzhou, Peoples' Republic of China.
authors.forename: Xiaoling
authors.initials: X
authors.lastname: Deng
mesh_terms: D020561:Alphaproteobacteria / Q000201:enzymology / Q000235:genetics; D001426:Bacterial Proteins / Q000378:metabolism; D002957:Citrus / Q000382:microbiology*; D018628:Gene Dosage; D010935:Plant Diseases / Q000382:microbiology*; D016133:Polymerase Chain Reaction; D012264:Ribonucleotide Reductases / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D012264:Ribonucleotide Reductases