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Title: Changes in potato phenylpropanoids during tuber development

Author
item Navarre, Duroy - Roy
item PAYYAVULA, RAJA - Washington State University
item SHAKYA, ROSHANI - Washington State University
item KNOWLES, RICHARD - Washington State University
item KUMAR, SYAM - Washington State University

Submitted to: Plant Physiology and Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/4/2013
Publication Date: 1/28/2013
Citation: Navarre, D.A., Payyavula, R., Shakya, R., Knowles, R., Kumar, S. 2013. Changes in potato phenylpropanoids during tuber development. Plant Physiology and Biochemistry. 65:89-101.

Interpretive Summary: Potatoes contain compounds called phenolics that have antioxidant or other health-promoting properties. How these compounds change during potato development was examined and immature potatoes were found to have higher amounts. Expression of some of the genes involved were also higher earlier in tuber development and sugars increase the amount of tuber antioxidants. Understanding the mechanisms that govern tuber phenolic concentrations will lead to even more nutritious potatoes. These findings suggest consumption of immature potatoes (known as "new potatoes" or "baby potatoes" would increase the dietary intake of phytonutrients and may appeal to health-conscious consumers.

Technical Abstract: Phenylpropanoid metabolite and transcript expression during different developmental stages were examined in field grown potatoes. Carbohydrate and shikimic acid metabolism was assessed to determine how tuber primary metabolism influences phenylpropanoid metabolism. Phenylpropanoid concentrations were highest in immature tubers, as were some transcript levels and enzyme activities including phenylalanine ammonia lyase (PAL). Phenylpropanoid concentration differences between mature and immature tubers varied by genotype, but in some cases were approximately three-fold. The most abundant phenylpropanoid was chlorogenic acid (5CGA), which decreased during tuber maturation. Hydroxycinnamoyl-CoA:quinate hydroxycinnamoyl transferase (HQT) transcripts were highly expressed relative to other phenylpropanoid genes, but were not well correlated with 5CGA concentrations (r ¼ _0.16), whereas HQT enzyme activity was. In contrast to 5CGA, less abundant chlorogenic isomers increased during development. Concentrations of hydroxycinnamic acid amides were higher in immature tubers, as was expression of arginine- and ornithine decarboxylases. Expression of several genes involved in carbohydrate or shikimate metabolism, including sucrose synthase and DAHP, showed similar developmental patterns to phenylpropanoid pools, as did shikimate dehydrogenase enzyme activity. Sucrose, glucose and fructose concentrations were highest in immature tubers. Exogenous treatment of potatoes with sugars stimulated phenylpropanoid biosynthesis, suggesting sugars contribute to the higher phenylpropanoid concentrations in immature tubers. These changes in phenylpropanoid expression suggest the nutritional value of potatoes varies during development.'