Gene Expression Associated with Wound and Native Periderm Maturation in Potato Tubers
Neubauer, Jonathan David
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Potato (Solanum tuberosum L.) is the world's fourth largest food crop and large financial losses are incurred each year from wound and bruise related injuries. However, little is known about the coordinate induction of genes that may be associated with, or mark major wound-healing and periderm maturation events. Also, one of the key defense mechanisms for potato tubers is the robust barrier provided by the phellem (skin) of the native periderm. Many biological processes are involved in the formation of this stout tissue. However, little is known about induction of genes that may be associated with this process. The objectives of this research were to molecularly assess the processes of wound periderm development and maturation, and native periderm maturation in potato tubers. In this study, these processes were determined in coordination with expression profiles of selected genes. The cell cycle, cell wall protein, and pectin methyl esterase genes were determined from two diverse potato genotypes and two harvests NDTX4271-5R (ND) and Russet Burbank (RB) tubers; 2008 and 2009 harvests. Cell cycle genes encoding epidermal growth factor binding protein (StEBP), cyclin-dependent kinase B (StCDKB), and cyclin-dependent kinase regulatory subunit (StCKS1At) expression profiles were coordinated with related phellogen formation and the induction and cessation of phellem cell formation. Genes encoding the structural cell wall proteins extensin (StExt1) and extensin-like (StExtlk) expression profiles suggested involvement with closing layer formation and subsequent phellem cell layer formations. The coordinate induction and expression profile of StTLRP, a gene encoding a cell wall strengthening "tyrosine- and lysine-rich protein," suggested a role in the formation of the closing layer followed by phellem cell generation and lastly cell wall thickening in nonmeristematic phellogen cells. StPME and StPrePME expression increased during periderm development, implicating involvement in modifications for closing layer and phellem cell formation. Collectively, these results indicate that the genes monitored were involved in and their expression profiles markedly coordinated with periderm formation and the on-set of periderm maturation; results were more influenced by harvest than genotype. Importantly, StTLRP was the only gene examined that may be involved in phellogen cell wall strengthening or thickening after cessation of cell division.