Distribution of amylases within sweet potato (Ipomoea batatas L.) root tissue

Hagenimana, V.; Vézina, Louis‐P.; Simard, R.E.

doi:10.1021/jf00022a010

Cited by 41 publications

(30 citation statements)

References 28 publications

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“…phloem-specific enzyme as identified by RS 5 using immunofluorescence microscopy, although it was, at first, difficult to reconcile our strict phloem localization with earlier localization studies (Okamoto and Akazawa, 1979;Chang and Su, 1986;Beck and Ziegler, 1989;Hagenimana et al, 1992). One possible explanation for our results is that we used a monoclonal antibody rather than a polyclonal serum raised against P-amylase.…”

Section: Discussioncontrasting

confidence: 49%

“…A vacuolar site for the enzyme was suggested as the result of cell fractionation studies (Beck and Ziegler, 1989). Other studies based on polyclonal antibodies raised against /3-amylase (Okamoto and Akazawa, 1979;Hagenimana et al, 1992) have suggested an association with starch grains. Polyclonal antibodies raised against an inhibitor of starch phosphorylase, which was later shown to be /3-amylase (Pan et al, 1988), labeled cell walls and starch granules in paraffin sections of sweet potato (Chang and Su, 1986).…”

Section: Discussionmentioning

confidence: 92%

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Identification and Characterization of a Phloem-Specific [beta]-Amylase

1995

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A monoclonal antibody, RS 5, was raised by injecting sieve elements isolated from tissue cultures of Sfrepfanfhus forfuosus (Brassicaceae) into BALB/c mice and screening resultant hybridoma supernatants for the labeling of phloem using immunofluorescence microscopy. The RS 5 monoclonal antibody identifies a 57-kD protein on immunoblots, which is present in phloem-forming tissue cultures of S. fortuosus but is absent in cultures that lack phloem. Purified 57-kD protein of S. forfuosus is demonstrated to be a phloem-specific /3-amylase. Partia1 peptide sequences of the 57-kD protein of S. fortuosus are shown to be 96% identical with the corresponding portions of a deduced sequence reported for a major form of /3-amylase in Arabidopsis thaliana. The RS 5 antibody cross-reacts with the major form of A. thaliana /3-amylase on immunoblots, and the antibody also binds to the sieve elements of A. thaliana using immunofluorescence microscopy. The results suggest that the major form of A. thaliana /3-amylase is a phloem-specific enzyme.

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Section: Discussioncontrasting

confidence: 49%

Section: Discussionmentioning

confidence: 92%

Identification and Characterization of a Phloem-Specific [beta]-Amylase

1995

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“…The fact that ␤-amylases hydrolyze starch in vitro (Beck and Ziegler, 1989) suggests a role for ␤-amylases in starch degradation. In addition, immunolocalization studies have shown an apparent association between ␤-amylases and starch granules (Okamoto and Akazawa, 1979;Hagenimana et al, 1992). However, these studies were conducted using polyclonal antibodies that may cross-react with starch phosphorylase.…”

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confidence: 99%

The ram1 Mutant of Arabidopsis Exhibits Severely Decreased β-Amylase Activity

2001

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Despite extensive biochemical analyses, the biological function(s) of plant ␤-amylases remains unclear. The fact that ␤-amylases degrade starch in vitro suggests that they may play a role in starch metabolism in vivo. ␤-Amylases have also been suggested to prevent the accumulation of highly polymerized polysaccharides that might otherwise impede flux through phloem sieve pores. The identification and characterization of a mutant of Arabidopsis var. Columbia with greatly reduced levels of ␤-amylase activity is reported here. The reduced ␤-amylase 1 (ram1) mutation lies in the gene encoding the major form of ␤-amylase in Arabidopsis. Although the Arabidopsis genome contains nine known or putative ␤-amylase genes, the fact that the ram1 mutation results in almost complete loss of ␤-amylase activity in rosette leaves and inflorescences (stems) indicates that the gene affected by the ram1 mutation is responsible for most of the ␤-amylase activity present in these tissues. The leaves of ram1 plants accumulate wild-type levels of starch, soluble sugars, anthocyanin, and chlorophyll. Plants carrying the ram1 mutation also exhibit wild-type rates of phloem exudation and of overall growth. These results suggest that little to no ␤-amylase activity is required to maintain normal starch levels, rates of phloem exudation, and overall plant growth.␤-Amylases are found in vegetative tissues as well as in storage and reproductive organs, such as tubers and seeds. ␤-Amylases hydrolyze ␣-1,4-glucosidic linkages from the reducing ends of polysaccharide chains to form maltose (Beck and Ziegler, 1989). The genomes of many plant species contain several genes that encode ␤-amylases. For example, according to the database maintained by The Institute for Genomic Research (TIGR), the Arabidopsis genome includes nine genes that are identified as ␤-amylase or putative ␤-amylase genes (http://www.tigr.org/ tdb/edb2/ath1/htmls/GeneNameSearch.html). Despite the fact that they have been well characterized in vitro, the in vivo biological function(s) of ␤-amylases remains under debate (Ziegler, 1999).Several functions have been proposed for ␤-amylases in vivo. The fact that ␤-amylases hydrolyze starch in vitro (Beck and Ziegler, 1989) suggests a role for ␤-amylases in starch degradation. In addition, immunolocalization studies have shown an apparent association between ␤-amylases and starch granules (Okamoto and Akazawa, 1979;Hagenimana et al., 1992). However, these studies were conducted using polyclonal antibodies that may cross-react with starch phosphorylase. Consequently, the results of these studies should be interpreted with caution (Wang et al., 1995). In addition, starch is localized to plastids, whereas most ␤-amylases lack chloroplast transit peptides (Kreis et al., 1987;Monroe et al., 1991;Yoshida and Nakamura, 1991). Although chloroplast-localized ␤-amylases have been identified (Lao et al., 1999), the majority of ␤-amylase activity is extrachloroplastic (Beck and Ziegler, 1989;Nakamura et al., 1991). For example, 80% of the amylas...

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“…4, 5). Similarly, sweet potato accumulates both β-amylase and starch throughout the whole tuber (Hagenimana et al, 1992). This suggests that the β-amylase may have little relation to the digestion of endogenous starch in the wasabi rhizome and sweet potato tuber.…”

Section: Resultsmentioning

confidence: 99%