Translucent tissue defect in potato (Solanum tuberosum L.) tubers is associated with oxidative stress accompanying an accelerated aging phenotype

Abstract

Translucent tissue defect (TTD) is an undesirable postharvest disorder of potato tubers characterized by the development of random pockets of semi-transparent tissue containing high concentrations of reducing sugars. Translucent areas turn dark during frying due to the Maillard reaction. The newly released cultivar, Premier Russet, is highly resistant to low temperature sweetening, but susceptible to TTD. Symptoms appeared as early as 170 days after harvest and worsened with time in storage (4-9 °C, 95 % RH). In addition to higher concentrations of glucose, fructose and sucrose, TTD resulted in lower dry matter, higher specific activities of starch phosphorylase and glc-6-phosphate dehydrogenase, higher protease activity, loss of protein, and increased concentrations of free amino acids (esp. asparagine and glutamine). The mechanism of TTD is unknown; however, the disorder has similarities with the irreversible senescent sweetening that occurs in tubers during long-term storage, where much of the decline in quality is a consequence of progressive increases in oxidative stress with advancing age. The respiration rate of non-TTD 'Premier Russet' tubers was inherently higher (ca. 40 %) than that of 'Russet Burbank' tubers (a non-TTD cultivar). Moreover, translucent tissue from 'Premier Russet' tubers had a 1.9-fold higher respiration rate than the average of non-translucent tissue and tissue from non-TTD tubers. Peroxidation of membrane lipids during TTD development resulted in increased levels of malondialdehyde and likely contributed to a measurable increase in membrane permeability. Superoxide dismutase and catalase activities and the ratio of oxidized to total glutathione were substantially higher in translucent tissue. TTD tubers also contained twofold less ascorbate than non-TTD tubers. TTD appears to be a consequence of oxidative stress associated with accelerated aging of 'Premier Russet' tubers.

Low oxygen storage modulates invertase activity to attenuate cold-induced sweetening and loss of process quality in potato (Solanum tuberosum L.)

“…The pelleted protein (10,000g, 20 min, 4 o C) was resolubilized in the original extraction buffer (without PVPP) and stored at -18 o C until further analysis. Acid invertase activity was measured colorimetrically in the presence (basal activity) and absence (total activity) of its endogenous inhibitor by a microplate modification of Brummell et al (2011) as outlined in Zommick et al (2013).…”

Genome-wide transcriptome profiling reveals novel insights into Luffa cylindrica browning

“…The regulation of a transcript annotated as starch phosphorylase (SP), which is responsible for the phosphorolytic degradation of starch [28,31], was low in the YLB05 library (Table 3). Observations revealed that elevated SP expression and activity in translucent potato tubers was in accordance with decreased starch, increased reducing sugars and dark color [41]. The abundance of SP increased significantly in postharvest XTR05 and might be a factor contributing to its high BI.…”

Independent translation of ORFs in dicistronic operons, synthetic building blocks for polycistronic chloroplast gene expression

“…Immunoblot analyses was carried out following the protocol described for potato tubers (Zommick et al ., 2013). Briefly, total soluble protein was extracted from leaf and root samples frozen in liquid nitrogen and pulverized using stainless steel grinding balls (SPEX Sample Prep, Metuchen, NJ, USA).…”