To identify the genes involved in nodule formation and to increase usable molecular probes, a cDNA library of Astragalus sinicus genes specifically expressed in infected roots by Mesorhizobium huakuii 7653R is generat...To identify the genes involved in nodule formation and to increase usable molecular probes, a cDNA library of Astragalus sinicus genes specifically expressed in infected roots by Mesorhizobium huakuii 7653R is generated using a PCR-based suppressive subtractive hybridization (SSH) technique with two mRNA populations of infected and uninfected control roots. Two nodule-specific genes, AsIIC259 and AsG2511, are identified from infected roots of A. sinicus. The amino acid sequences deduced from the open reading frames (ORFs) reveal that AsIIC259 and AsG2511 encodes a polypeptide with 134 and 58 amino acids, respectively. A signal peptide sequence is predicted with high probability at the N-termini of the AsIIC259 and AsG2511. The motif searches show that the deduced polypeptide of AsIIC259 con- tains two N-glycosylation sites, a cAMP- and cGMP-dependent protein kinase phosphorylation site and a casein kinase II phosphorylation site. BLASTP searches reveal that AsIIC259 putative protein displays a low degree of similarity to a unique nodulin from Lupinus luteus nodules. No significant identity is displayed over the predicted polypeptides of AsG2511 with any published sequences. Virtual Northern blot and semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) analyses indicate that the two genes are expressed exclusively in inoculated roots and that their expression is 2―4 d later than that of the leghaemoglobin (Lb) gene during nodule development.展开更多
基金Supported by the National Basic Research Program of China (Grant No. 2001CB108901)
文摘To identify the genes involved in nodule formation and to increase usable molecular probes, a cDNA library of Astragalus sinicus genes specifically expressed in infected roots by Mesorhizobium huakuii 7653R is generated using a PCR-based suppressive subtractive hybridization (SSH) technique with two mRNA populations of infected and uninfected control roots. Two nodule-specific genes, AsIIC259 and AsG2511, are identified from infected roots of A. sinicus. The amino acid sequences deduced from the open reading frames (ORFs) reveal that AsIIC259 and AsG2511 encodes a polypeptide with 134 and 58 amino acids, respectively. A signal peptide sequence is predicted with high probability at the N-termini of the AsIIC259 and AsG2511. The motif searches show that the deduced polypeptide of AsIIC259 con- tains two N-glycosylation sites, a cAMP- and cGMP-dependent protein kinase phosphorylation site and a casein kinase II phosphorylation site. BLASTP searches reveal that AsIIC259 putative protein displays a low degree of similarity to a unique nodulin from Lupinus luteus nodules. No significant identity is displayed over the predicted polypeptides of AsG2511 with any published sequences. Virtual Northern blot and semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) analyses indicate that the two genes are expressed exclusively in inoculated roots and that their expression is 2―4 d later than that of the leghaemoglobin (Lb) gene during nodule development.
