Characterization and expression of a novel thaumatin-like protein (CcTLP1) from papaveraceous plant Corydalis cava

Thaumatin-like proteins (TLPs, osmotins) form a protein family which shares a significant sequence homology to the sweet-tasting thaumatin from the plant Thaumatococcus daniellii. TLPs are not sweet-tasting and are involved in response to biotic stresses and developmental processes. Recently it has been shown using a proteomic approach that the tuber extract from Corydalis cava (Papaveraceae) contains a TLP protein. The aim of this work was to characterize the structure and expression of TLP from C. cava tubers. The results obtained using a PCR approach with degenerate primers demonstrated a coding sequence of a novel protein, named CcTLP1. It consists of 225 aa, has a predicted molecular weight of 24.2 kDa (NCBI GenBank accession no. KJ513303) and has 16 strictly conserved cysteine residues, which form 8 disulfide bridges and stabilize the 3D structure. CcTLP1 may be classified into class IX of plant TLPs. The highest CcTLP1 expression levels were shown by qPCR in the stem of the plant compared to other organs and in the medium-size plants compared to other growth phases. The results confirm that CcTLP1 is expressed during plant growth and development until flowering, with a possible defensive function against different stress conditions.