Polygalacturonase Gene Expression in Rutgers, rin, nor, and Nr Tomato Fruits

Abstract

ABSTRACrPolygacturonse (PG) The ripening of tomato fruit is characterized by a series of coordinated biochemical and physiological changes which collectively contribute to the final texture, color, and flavor ofthe ripe fruit. The softening of tomato fruit during ripening has been studied extensively during the past 20 years and a large body of evidence has accumulated which suggests the cell wall enzyme PG2 plays a major role in this process. Several lines of evidence which support this include: (a) a rough correlation between levels of extractable PG activity and the rate of softening for a number of tomato cultivars (6, 13); (b) a lack of correlation between the activity of other cell wall enzymes (e.g. cellulase and A3-1,3-glucanase) and the rate of fruit softening (14, 29); (c) similarities between in vivo cell wall degradation products during ripening and in vitro cell wall products released by the action of purified PG on isolated fruit cell walls (15,30); and (d) the demonstration that slow ripening cultivars and nonripening tomato mutants are deficient in PG activity (6,22,28). Although these lines of evidence suggest a major role for PG in softening, other factors such as the levels of free and bound Ca2" in the cell wall and substrate accessibility may also be important (7).Recently, several groups have studied changes in gene expres- ' Supported by gifts from Chesebrough-

Activity and expression of polygalacturonase vary at different fruit ripening stages of sweet pepper cultivars

“…The results are similar to the findings of scientists who worked on the role of PG during fruit development in various kinds of fruits and found a correlation, as PG activity and softening occurs simultaneously in cherry (Barrett and Gonzalez, 1994), date (Hasegawa et al, 1969), durian (Ketsa and Daengkanit, 1999), kiwifruit (Wang et al, 2000), mango (Ketsa et al, 1998), papaya (Paull and Chen, 1983), pear (Ahmed and Labavitch, 1980), pepper (Rao and Paran, 2003;Arancibia and Motsenbocker, 2006), tobacco (Osteryoung et al, 1990), and tomato (Hobson, 1965;Crookes and Grierson, 1983;Huber, 1983;DellaPenna et al, 1987;Bird et al, 1988;Biggs and Handa, 1989;Smith et al, 1990;Fenwick et al, 1996).…”

“…The deduced amino acid sequence of CaPG showed most similarity to active endo-PG enzyme isolated by Chen et al (2010). There was little expression of CaPG in the green stage of both cultivars, as also found by DellaPenna et al (1987); Daengkanit, (1999), andWang et al (2000) reported that PG is not expressed at early stages of fruit maturity. CaPG expression was quite weak during the breaker stage in cv.…”

“…Softening of the tomato fruit during ripening has been studied extensively over the last 20 years, and a large body of evidence has accumulated, suggesting that the cell wall enzyme PG plays an inevitable role in this process (DellaPenna et al, 1987). The softening phenomenon influenced by PG in fruits like apples, cherries, dates, durians, grapes, kiwis, melons, peaches, pears, pineapples, tobacco, and tomatoes during ripening has been studied during the past two decades and substantial evidence has been collected, suggesting that the cell wall enzyme PG plays a major role in the entire ripening process (Hobson, 1965;Hasegawa et al, 1969;Ahmed and Labavitch, 1980;Paull and Chen, 1983;Osteryoung et al, 1990;Barrett and Gonzalez, 1994;Ketsa et al, 1998;Ketsa and Daengkanit, 1999).…”

“…The primary cell wall is composed of several polymers, including cellulose, glycans and pectins that are modified during fruit ripening (Brummell and Harpster, 2001;Giovannoni, 2001). The ripening of fruit is characterized by a series of coordinated biochemical and physiological changes, which collectively leads into the final texture, color and taste of the mature fruit (DellaPenna et al, 1987).…”

Analysis of tomato polygalacturonase expression in transgenic tobacco.

“…Protein was extracted from tobacco tissue essentially as previously described for tomato fruit tissue (DellaPenna et al, 1987). Briefly, leaf tissue was homogenized on ice in 1 volume to 3 volumes of 20 mM Tris, 5 mM 2-mercaptoethanol, pH 7, or 20 mM Mes, 3 mM DTT, pH 5.5 (low-salt buffers).…”