Biochemical changes in secondary metabolites in wounded and deteriorated cassava roots.

Abstract

Bluish fluorescent and phenolic components were produced in cassava roots in response to cutinjury, and in relation to physiological deterioration and microbial deterioration. The former proved to consist of five coumarin components, the main three of whichwere scopoletin, scopolin and esculin, and the other two were scopoletin-and esculetin-containing conjugates. A main component of the latter was (+)-catechin. Some enzymes pertaining to the production of the secondary metabolites such as acid invertase, phenylalanine ammonialyase and peroxidase were formed in cut-injured tissue and in non-infected tissue adjacent to the soft-rotten part. Cassava roots easily deteriorate during storage soon after harvest, and the deteriorative nature is classified into physiological (or primary) deterioration and microbial (or secondary) deterioration.1~4) The former involves brownish discoloration (so called vascular streaking) in the intervening part between the outermost and inner parts of parenchymatous tissue, and the latter is characterized by light brownish discoloration of the soft-rotten part and by blue-black pigmentation of the xylem vessels or extensive discoloration, light greyblack, of the non-rotten tissue adjacent to the rotten part. Such deterioration in cassava after harvest lowers the food quality and is a serious problem for a number of the people in tropical regions for whomcassava roots are the main staple. Therefore, the Tropical Products Institute

Large-Scale Proteomics of the Cassava Storage Root and Identification of a Target Gene to Reduce Postharvest Deterioration

“…2-Oxoglutarate-dependent dioxygenase, which was recently identified as a pivotal enzyme converting feruoyl-CoA into 69-hydroxyferuoyl-CoA during scopoletin synthesis (Kai et al, 2008), was upregulated during PPD progression only 12 h after harvest. PAL, which initiates phenylpropanoid synthesis, also had increased activity during PPD (Tanaka et al, 1983). We found that both PAL1 and PAL2 abundances were regulated, with up to an 8-fold increase at 24 h after harvest (Supplemental Figure 9).…”

“…The coumarin scopoletin accumulates to high levels during PPD progression (Tanaka et al, 1983;Wheatley and Schwabe, 1985;Buschmann et al, 2000b;Bayoumi et al, 2010). Enzymes involved in the final steps of scopoletin biosynthesis were significantly upregulated 6 h after harvest (Supplemental Figure 8), including 4-coumarate-CoA ligase and caffeoyl-CoA O-methyltransferase enzymes, which convert 4-coumarate into coumaroyl-CoA and caffeoyl-CoA into feruoylCoA, respectively.…”

“…However, changes in protein accumulation, interactions, modifications, and activities during PPD development are equally important but currently not well understood. Earlier investigations revealed that PPD is associated with changes in the activities of enzymes such as catalase, superoxide dismutase, phenylalanine ammonia lyase (PAL), and peroxidase (Tanaka et al, 1983;Rickard, 1985;Reilly et al, 2001Reilly et al, , 2004.…”

Induced plant secondary metabolites for phytopatogenic fungi control: a review

“…The main constituents induced were identified as umbelliferone (12) and scopoletin (13), and the minor ones esculetin and the two ß-D-glucosides such as scopolin and skimminn (Uritani and Hoshiya, 1953;Minamikawa et al, 1962;Tanaka et al, 1983;Minamikawa et al, 1964). In addition, several authors have been reported that scoparone (6,7-dimethoxycoumarin) (14) is the main phytoalexin involved in induced defense mechanism of citrus against pathogens such as Phytophthora parasitica (Afek, et al, 1986), Guignardia citricarpa (De Lange et al, 1976), Penicillium digitatum (Kim et al, 1992) and Diaporthe citri (Arimoto et al, 1986).…”

Cassava: A Basic Energy Source in the Tropics

“…It is characterized by a blue-black discoloration of the xylem vessels known as "vascular streaking" The onset of PPD is associated with an increase in respiration (Uritani, 1998;Hirose, 1984), changes in lipid composition (Lalaguna and Agudo, 1989), synthesis of ethylene (Hirose, 1984). accumulation of secondary metabolites from the phenylpropanoid pathway, and increases in many enzyme activities, including PAL and chalcone synthase, glucanase, chitinase, proteinase inhibitors, HRGPs, invertase, catalase, dehydrogenase, peroxidase, and polyphenol oxidase (Rickard, 1981;Tanaka et al, 1983). Wounding of cassava roots enhances respiration rates within the first day, which is followed by primary physiological deterioration (Uritani, 1998;Uritani and Reyes, 1984).…”