Submitted to: Plant Biotechnology Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/23/2007
Publication Date: 11/1/2007
Citation: Speransky, A.S., Krinitsina, A.A., Poltronieri, P., Fasano, P., Cimaglia, F., Santino, A., Bogacheva, A.M., Shevelev, A.B., Halterman, D.A., Valueva, T.A. 2007. Kunitz-type protease inhibitors group B from Solanum palustre. Plant Biotechnology Journal. 2(11):1417-1424. Interpretive Summary: Cultivated potato (Solanum tuberosum L.) is an important crop worldwide and is the member of a diverse family of plants (Solanaceae). The genetic diversity present within the Solanaceae offers unique opportunities to study gene families in related but sexually incompatible species. Genetically, wild and cultivated potatoes are closely related and the transfer of genes between species, though sometimes laborious, is possible. Wild potato species offer a source of unique genes that can be introduced into cultivated varieties and contribute significantly to resistance against multiple diseases. Potato tubers contain an abundance of proteins that have significant proteinase inhibitor (PI) activity that is thought to play a role in defense against chemicals introduced during insect and pathogen attack. One group of PI in potato are the Kunitz-type protease inhibitors (KPI). We found differences between KPI proteins from cultivated potato and a wild relative of the potato, Solanum palustre, a non-tuberous South-American species. Our results will help plant breeders make decisons about intercrossing genes that protect against several potato diseases from S. palustre into S. tuberosum.
Technical Abstract: Five Kunitz protesase inhibitor group B genes were isolated from the genome of the diploid nontuber-forming potato species Solanum palustre. Three of five new genes share 99% identity to the published KPI-B genes from various cultivated potato accessions, while others exhibit 96% identity. Spls-KPI-B2 and Spls-KPI-B4 proteins contain unique substitutions of the most conserved residues usually involved to trypsin and chymotrypsin-specific binding sites of Kunitz-type protease inhibitor (KPI)-B, respectively. To test the inhibition of trypsin and chymotrypsin by Spls-KPI proteins, five of them were produced in E. coli purified using a Ni-sepharose resin and ion-exchange chromatography. All recombinant Spls-KPI-B inhibited trypsin; Ki values ranged from 84.8 (Spls-KPI-B4), 345.5 (Spls-KPI-B1), and 1310.6 nM (Spls-KPI-B2) to 3883.5 (Spls-KPI-B5) and 8370 nM (Spls-KPI-B3). In addition, Spls-KPI-B1 and Spls-KPI-B4 inhibited chymotrypsin. These data suggest that regardless of substiutions of key active-center residues both Spls-KPI-B4 and Spls-KPI-B1 are functional trypsin-chymotrypsin inhibitors.