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Insights into the effects of polygalacturonase FaPG1 gene silencing on pectin matrix disassembly, enhanced tissue integrity, and firmness in ripe strawberry fruits.

ABSTRACT: Antisense-mediated down-regulation of the fruit-specific polygalacturonase (PG) gene FaPG1 in strawberries (Fragaria×ananassa Duch.) has been previously demonstrated to reduce fruit softening and to extend post-harvest shelf life, despite the low PG activity detected in this fruit. The improved fruit traits were suggested to be attributable to a reduced cell wall disassembly due to FaPG1 silencing. This research provides empirical evidence that supports this assumption at the biochemical, cellular, and tissue levels. Cell wall modifications of two independent transgenic antisense lines that demonstrated a >90% reduction in FaPG1 transcript levels were analysed. Sequential extraction of cell wall fractions from control and ripe fruits exhibited a 42% decrease in pectin solubilization in transgenic fruits. A detailed chromatographic analysis of the gel filtration pectin profiles of the different cell wall fractions revealed a diminished depolymerization of the more tightly bound pectins in transgenic fruits, which were solubilized with both a chelating agent and sodium carbonate. The cell wall extracts from antisense FaPG1 fruits also displayed less severe in vitro swelling. A histological analysis revealed more extended cell-cell adhesion areas and an enhanced tissue integrity in transgenic ripe fruits. An immunohistological analysis of fruit sections using the JIM5 antibody against low methyl-esterified pectins demonstrated a higher labelling in transgenic fruit sections, whereas minor differences were observed with JIM7, an antibody that recognizes highly methyl-esterified pectins. These results support that the increased firmness of transgenic antisense FaPG1 strawberry fruits is predominantly due to a decrease in pectin solubilization and depolymerization that correlates with more tightly attached cell wall-bound pectins. This limited disassembly in the transgenic lines indicates that these pectin fractions could play a key role in tissue integrity maintenance that results in firmer ripe fruit.

SUBMITTER: Pose S

PROVIDER: S-EPMC3745733 | biostudies-literature | 2013 Sep

REPOSITORIES: biostudies-literature

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Insights into the effects of polygalacturonase FaPG1 gene silencing on pectin matrix disassembly, enhanced tissue integrity, and firmness in ripe strawberry fruits.

Posé Sara S Paniagua Candelas C Cifuentes Manuel M Blanco-Portales Rosario R Quesada Miguel A MA Mercado José A JA

Journal of experimental botany 20130719 12

Antisense-mediated down-regulation of the fruit-specific polygalacturonase (PG) gene FaPG1 in strawberries (Fragaria×ananassa Duch.) has been previously demonstrated to reduce fruit softening and to extend post-harvest shelf life, despite the low PG activity detected in this fruit. The improved fruit traits were suggested to be attributable to a reduced cell wall disassembly due to FaPG1 silencing. This research provides empirical evidence that supports this assumption at the biochemical, cellul ...[more]

PMID: 23873994

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Project description:The role of auxin in ripening strawberry (Fragaria ×ananassa) fruits has been restricted to the early stages of development where the growth of the receptacle is dependent on the delivery of auxin from the achenes. At later stages, during enlargement of the receptacle, other hormones have been demonstrated to participate to different degrees, from the general involvement of gibberellins and abscisic acid to the more specific of ethylene. Here we report the involvement of auxin at the late stages of receptacle ripening. The auxin content of the receptacle remains constant during ripening. Analysis of the transcriptome of ripening strawberry fruit revealed the changing expression pattern of the genes of auxin synthesis, perception, signaling and transport along with achene and receptacle development from the green to red stage. Specific members of the corresponding gene families show active transcription in the ripe receptacle. For the synthesis of auxin, two genes encoding tryptophan aminotransferases, FaTAA1 and FaTAR2, were expressed in the red receptacle, with FaTAR2 expression peaking at this stage. Transient silencing of this gene in ripening receptacle was accompanied by a diminished responsiveness to auxin. The auxin activity in the ripening receptacle is supported by the DR5-directed expression of a GUS reporter gene in the ripening receptacle of DR5-GUS transgenic strawberry plants. Clustering by co-expression of members of the FaAux/IAA and FaARF families identified five members whose transcriptional activity was increased with the onset of receptacle ripening. Among these, FaAux/IAA11 and FaARF6a appeared, by their expression level and fold-change, as the most likely candidates for their involvement in the auxin activity in the ripening receptacle. The association of the corresponding ARF6 gene in Arabidopsis to cell elongation constitutes a suggestive hypothesis for FaARF6a involvement in the same cellular process in the growing and ripening receptacle.

Dataset Information

Insights into the effects of polygalacturonase FaPG1 gene silencing on pectin matrix disassembly, enhanced tissue integrity, and firmness in ripe strawberry fruits.

Publications

Insights into the effects of polygalacturonase FaPG1 gene silencing on pectin matrix disassembly, enhanced tissue integrity, and firmness in ripe strawberry fruits.

Similar Datasets

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