Protein turnover in potato tubers during development, long-term storage, and plant establishment

Sarah Marie Weeda

doi:10.7273/000006004

Potato tubers are vegetative propagules that accumulate and store carbohydrate, lipid, and protein reserves during growth. These reserves will be mobilized following a period of dormancy to support plant establishment. Protease inhibitors comprise up to 50% of soluble proteins in tubers and may be involved in regulating proteolysis during protein mobilisation and accumulation. Potato multicystatin (PMC) is a cysteine (Cys) type protease inhibitor with eight inhibitory domains. While studies attribute insect antifeedant activity to PMC, little is known about its intrinsic biological function(s) during tuber development, dormancy, and sprouting. In vitro studies in our lab (Kumar et al., 1999) demonstrated that PMC inhibits patatin (tuber storage protein) degradation by tuber-derived Cys-proteases and thus PMC may have a role in regulating protein accumulation in tubers during development by inhibiting proteolysis and shifting the equilibrium between protein synthesis and catabolism toward synthesis. Detailed information linking PMC and other protease inhibitors to changes in protein content of tubers is lacking. This study focuses on defining changes in tuber protein content in relation to PMC levels and protease activity from tuber initiation to full maturity, through long-term storage, and during plant establishment from seed-tubers. During tuber development, the proteolytic activity was highest in non-tuberized stolons where PMC levels were undetectable. As PMC levels increased with tuberization, protease activity declined precipitously with a concomitant increase in patatin. During plant establishment from single-eye seedcores, total protease activity increased gradually during sprouting. A concomitant decline (3-fold) in total protein characterized the mobilization of protein reserves during plant establishment. Protein content of seedcores was inversely correlated with protease activity and positively related to PMC content. Similar trends were observed during long-term storage. Collectively, these results indicate that PMC, as a Cys-type protease inhibitor, likely has a role in modulating protein content of tubers by regulating protease activity. During tuber development, PMC facilitates protein deposition by inhibiting proteolysis. During plant establishment and long-term storage, decreasing PMC levels facilitate proteolysis of storage proteins, thus providing nitrogen for developing plants. Elucidation of the mechanisms controlling developmentally-linked changes in PMC content of tubers requires further investigation.

Protein turnover in potato tubers during development, long-term storage, and plant establishment

Files and links (1)

Abstract

Metrics

Details