Metabolite profiling of potato (Solanum tuberosum) tubers during wound-induced suberization

Suberin, a cell specific, wall-associated biopolymer, is formed during normal plant growth and development as well as in response to stress conditions such as wounding. It is characterized by the deposition of both a poly(phenolic) domain (SPPD) in the cell wall and a poly(aliphatic) domain (SPAD) thought to be deposited between the cell wall and plasma membrane. Although the monomeric components of suberin are well known, its biosynthesis and deposition is poorly understood. Using wound healing potato (Solanum tuberosum) tuber as a model system, a targeted metabolite analysis was performed. The accumulation patterns of suberin aliphatics (including the soluble pool and the SPAD) and the flux of carbon into the aliphatic monomers of the SPAD were tracked in a time course fashion. From these analyses, It is demonstrated that newly formed fatty acids undergo one of two main metabolic fates during wound-induced suberization: (1) desaturation followed by oxidation to form the 18:1 o-hydroxy and dioic acids, characteristic of potato suberin, and (2) elongation to very long chain fatty acids (C20 to C28), associated with reduction to 1-alkanols, decarboxylation to n-alkanes and minor amounts of hydroxylation.;To better understand the biosynthesis of suberin from a more global perspective, a metabolite profiling study was further conducted. Both soluble polar and soluble non-polar metabolite profiles were created in a time course fashion. Cluster analyses (PCA and HCA) of these metabolic profiles allowed not only the visualization of the separation of the time series samples, but also the distinction of the most influential metabolites for cluster formation. Furthermore, pair-wise correlation analysis of these metabolites revealed some interesting associations between metabolites. It was concluded that the targeted metabolite analysis combined with carbon flux analysis illustrated metabolic regulation during wound healing process, and provided insight into the organization of fatty acid metabolism. The metabolite profiling study provided new insights into the complex suberization process. It allowed the visualization of different stages of wound-induced suberization, clear distinction between polar and non-polar metabolism, time delay and shift from non-induced to induced metabolism, and the clear separation of suberin-associated metabolites from those induced by wounding. Pairwise correlation analysis may further help to identify unknown metabolites and make the connection of them with other metabolites associated with suberization.;Keywords. Solanum tuberosum, wound-induced suberization, suberin poly(aliphatic) domain, suberin poly(phenolic) domain, targeted metabolite analysis, carbon flux analysis, metabolite profiling, PCA, HCA, pairwise correlation analysis.