Biochemical and molecular characterization of [alpha]-D-galactosidase from coffee beans

Marraccini Pierre, Rogers William John, Caillet Victoria, Deshayes Alain, Granato Dominique, Lausanne Françoise, Lechat Sylvianne, Pridmore David, Pétiard Vincent. 2005. Biochemical and molecular characterization of [alpha]-D-galactosidase from coffee beans. Plant Physiology and Biochemistry, 43 : 909-920.

https://doi.org/10.1016/j.plaphy.2005.08.010

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Résumé : [alpha]-D-Galactosidase ([alpha]-Gal; EC 3.2.1.22) is one of three principal enzymes involved in the modification or degradation of plant cell wall galactomannans. In the present paper it is shown that [alpha]-galactosidase activities in field-grown coffee beans are variable amongst cultivars of the two species investigated (Coffea arabica and C. canephora var. Robusta). Higher activities were found in Arabica cultivars. Using beans from greenhouse-cultivated C. arabica as a model, we showed that [alpha]-Gal activity was undetectable in the bean perispem tissue, but increased gradually during the endosperm development, to reach a peak at approximately 30 weeks after flowering (WAF) which coincided with the hardening of the endosperm. [alpha]-Gal-specific transcripts detected at 22 and 27 WAF accompanied the peak of [alpha]-Gal activity, but were reduced to be undetectable in mature beans at 30 WAF, while [alpha]-Gal activity still persisted. Two isoforms were distinguished in 2-DE profiles of crude protein extracts by N-terminal sequencing analysis. Analysis of two-dimensional gel electrophoresis profiles demonstrated that both isoforms accumulated in a linear fashion throughout grain maturation. [alpha]-Gal activity was also observed to increase to high levels during in vitro germination of coffee beans suggesting an important function of this enzyme in this process. [alpha]-Gal cDNA sequences from Arabica and Robusta were sequenced and their deduced proteins appeared to be very similar, differing by only eight amino acids. Southern-blot analysis suggests that the enzyme was encoded by at least two genes in C. arabica that could explain the existence of the two isoforms identified in 2-DE profiles.

Mots-clés Agrovoc : Coffea arabica, Coffea canephora, alpha galactosidase, mannane, paroi cellulaire, fève de café, développement biologique, germination, activité enzymatique, variété

Mots-clés complémentaires : Cultivar

Classification Agris : F60 - Physiologie et biochimie végétale
F30 - Génétique et amélioration des plantes

Champ stratégique Cirad : Axe 1 (2005-2013) - Intensification écologique

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