Degradation of Cell Wall Polysaccharides during Tomato Fruit Ripening

Abstract

Changes in neutral sugar, uronic acid, and protein content of tomato (Lycoperskon esculentum Mil) ceH wais during ripening were characterized. The only components to decline in amount were galactose, arabinose, and galacturonic acid. Isolated cel waDls of ripening fruit contained a water-soluble polyuronide, possibly a product of in vivo polygalacturonase action. This polyuronide and the one obtained by incubating walls from mature green fruit with tomato polygalacturonase contained relatively much less neutral sugar than did intact cel waUls. The ripening-related decline in galactose and arabinose content appeared to be separate from polyuronide solubilization. In the rn mutant, the postharvest loss of these neutral sugars occurred in the absence of polygalacturonase and polyuronide solubilization. The enzyme(s) responsible for the removal of galactose and arabinose was not identified; a tomato cell wall polysaccharide containing galactose and arabinose (6:1) was not hydrolyzed by tomato /8-galactosidase.

Caracterização física, físico-química, enzimática e de parede celular em diferentes estádios de desenvolvimento da fruta de figueira

“…A redução na porcentagem de pectina total a partir dos 45 dias coincide com a intensa atividade da PME e PG e conseqüente aumento na solubilização das pectinas (Figuras 1 e 2). A solubilização de polímeros pécticos e a perda de açú-cares neutros não-celulósicos têm sido relatadas durante o amadurecimento de manga [8], [28]; de pêra [2]; e de tomate [19]. No entanto, durante o processo de amadurecimento, podem ocorrer reações degradativas, mas também de síntese, conforme FISCHER et al [16], MITCHAN & McDONALD [28] e VILAS BOAS et al [40].…”

Cell Wall Metabolism in Ripening Fruit (IX. Synthesis of Pectic and Hemicellulosic Cell Wall Polymers in the Outer Pericarp of Mature Green Tomatoes (cv XMT-22)

“…This has led to the suggestion that certain hydrolytic enzymes are responsible for the dissolution of the middle lamella as well as for the degradation of the cell wall itself, thereby leading to a general loss of cohesion of the tissue, perceived as softening. This model is supported by anatomical work that demonstrated the breakdown of middle lamella polymers (Ben-Arie et al, 1979), by numerous studies characterizing the ripening-related changes in cell wall polymers (Gross and Wallner, 1979;Ahmed and * Corresponding author; e-mail jmlabavitch@ucdavis.edu; fax 1-916 -752-8502. Labavitch, 1980;Gross, 1984), and by studies that demonstrated increases in the activities of some putative cell wall polysaccharide hydrolases during ripening (Hobson, 1968;Tucker et al, 1982;Brady et al, 1983;Pressey, 1989; for review, see Fischer and Bennett, 1991).…”

“…In the CDTA / Na,CO,-soluble (combined pectic) fraction, the only significant difference between treatments was a higher Gal (about 35%) content in the in vivo control ( Table I). The lower Gal contents of the water-and CDTA/ Na,CO,-soluble fractions from the in vitro treatments undoubtedly reflect the ripening-related loss of wall galactan reported for all tomatoes studied, including cv Castlemart (Gross and Wallner, 1979;Campbell et al, 1990). Within tissue type, the outer discs had significantly more Rha than the inner discs.…”

“…Throughout the years, studies have focused largely on cell wall breakdown as the primary reason for softening (Gross and Wallner, 1979;Grierson and Tucker, 1983;Huber, 1983). This has led to the suggestion that certain hydrolytic enzymes are responsible for the dissolution of the middle lamella as well as for the degradation of the cell wall itself, thereby leading to a general loss of cohesion of the tissue, perceived as softening.…”

Processamento mínimo de mamão 'formosa'

“…Os pedaços quando submetidos ao corte 1 apresentaram maiores teores (P<0,05) de pectina total (0,52%) que os submetidos ao corte 2 (0,49%). De modo geral, pode-se observar que os teores de pectina total diminuíram com o tempo de armazenamento, o que pode estar relacionado a aumento da solubilidade em água dos poliuronídeos da parede celular e conseqüente amolecimento dos mesmos [6]. O efeito da temperatura, apesar da interação significativa com os outros parâme-tros, não se mostrou efetivo, dada a variação observada na Tabela 4.…”