cDNA cloning and expression analysis of a mannose-binding lectin from Pinellia pedatisecta.

Pinellia pedatisecta agglutinin (PPA)is a very basic protein that accumulates in the tuber of P.pedatisecta .PPA is a hetero-tetramer protein of 40 kDa,composed of two polypeptide chains A (about 12 kDa)and two polypeptides chains B (about 12 kDa).The full-length cDNA of PPA was cloned from P.pedatisecta using SMART RACE-PCR technology; it was 1146 bp and contained a 771 bp open reading frame (ORF)encoding a lectin precursor of 256 amino acid residues with a 24 amino acid signal peptide.The PPA precursor contained 3 mannose-binding sites (QXDXNXVXY) and two conserved domains of 43% identity,PPA-DOM 1 (polypeptides A)and PPA-DOM 2 (polypeptides B).PPA shared varying identities,ranging from 40% to 85%,with mannose-binding lectins from other species of plant families such as Araceae, Alliaceae, Iridaceae, Liliaceae, Amaryllidaceae and Bromeliaceae. Southern blot analysis indicated that ppa belonged to a multi-copy gene family. Expression pattern analysis revealed that ppa expressed in most tested tissues, with high expression being found in spadix,spathe and tuber.Cloning of the ppa gene not only provides a basis for further investigation of its structure,expression and regulatory mechanism,but also enables us to test its potential role in controlling pests and fungal diseases by transferring the gene into plants in the future.

Genomic cloning and characterization of a PPA gene encoding a mannose-binding lectin from Pinellia pedatisecta

A gene encoding a mannose-binding lectin, Pinellia pedatisecta agglutinin (PPA), was isolated from leaves of Pinellia pedatisecta using genomic walker technology. The ppa contained an 1140-bp 5'-upstream region, a 771-bp open reading frame (ORF) and an 829-bp 3'-downstream region. The ORF encoded a precursor polypeptide of 256 amino acid residues with a 24-amino acid signal peptide. There were one putative TATA box and six possible CAAT boxes lying in the 5'-upstream region of ppa. The ppa showed significant similarity at the nucleic acid level with genes encoding mannose-binding lectins from other Araceae species such as Pinellia ternata, Arisaema heterophyllum, Colocasia esculenta and Arum maculatum. At the amino acid level, PPA also shared varying homology (ranging from 40% to 85%) with mannose-binding lectins from other plant species, such as those from Araceae, Alliaceae, Iridaceae, Lillaceae, Amaryllidaceae and Bromeliaceae. The cloning of the ppa gene not only provides a basis for further investigation of PPA's structure, expression and regulation mechanism, but also enables us to test its potential role in controlling pests and fungal diseases by transferring the gene into tobacco and rice in the future