Antisense Down-Regulation of the FaPG1 Gene Reveals an Unexpected Central Role for Polygalacturonase in Strawberry Fruit Softening

The strawberry (Fragaria x ananassa 'Chandler') fruit undergoes a fast softening during ripening. Polygalacturonase (PG) activity is low during this process, but two ripening-related PG genes, FaPG1 and FaPG2, have been cloned. Both genes were up-regulated during fruit ripening and were al...

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Bibliographic Details
Published in:Plant physiology (Bethesda) 2009-06, Vol.150 (2), p.1022-1032
Main Authors: Quesada, Miguel A, Blanco-Portales, Rosario, Posé, Sara, García-Gago, Juan A, Jiménez-Bermúdez, Silvia, Muñoz-Serrano, Andrés, Caballero, José L, Pliego-Alfaro, Fernando, Mercado, José A, Muñoz-Blanco, Juan
Format: Article
Language:English
Subjects:
Biological and medical sciences
Blotting, Southern
Cell Wall - drug effects
Cell Wall - metabolism
Cell walls
Complementary DNA
Development and Hormone Action
Down-Regulation - drug effects
Down-Regulation - genetics
Enzymes
Fragaria - enzymology
Fragaria - genetics
Fruit - enzymology
Fruit - genetics
Fruit - growth & development
Fruits
Fundamental and applied biological sciences. Psychology
Gene expression
Gene Expression Profiling
Gene Expression Regulation, Enzymologic - drug effects
Gene Expression Regulation, Plant - drug effects
Genes, Plant
Indoleacetic Acids - pharmacology
Molecular Sequence Data
Phenotype
Plant physiology and development
Plant Proteins - genetics
Plant Proteins - metabolism
Plants
Plants, Genetically Modified
Polygalacturonase - metabolism
Postharvest handling
Ripening
RNA
RNA, Antisense - metabolism
Transgenic plants
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Summary:The strawberry (Fragaria x ananassa 'Chandler') fruit undergoes a fast softening during ripening. Polygalacturonase (PG) activity is low during this process, but two ripening-related PG genes, FaPG1 and FaPG2, have been cloned. Both genes were up-regulated during fruit ripening and were also negatively regulated by auxin. To further assess the role of FaPG1 on strawberry softening, transgenic plants containing an antisense sequence of this gene under the control of the 35S promoter (APG lines) were obtained. Sixteen out of 30 independent transgenic lines showed fruit yields similar to those of the control. Several quality parameters were measured in ripe fruits from these 16 lines. Fruit weight was slightly reduced in four lines, and most of them showed an increase in soluble solid content. Half of these lines yielded fruits significantly firmer than did the control. Four APG lines were selected, their ripened fruits being on average 163% firmer than the control. The postharvest softening of APG fruits was also diminished. Ripened fruits from the four selected lines showed a 90% to 95% decrease in FaPG1 transcript abundance, whereas the level of FaPG2 was not significantly altered. Total PG activity was reduced in three of these lines when compared with control fruits. Cell wall extracts from APG fruits showed a reduction in pectin solubilization and an increase in pectins covalently bound to the cell wall. A comparative transcriptomic analysis of gene expression between the ripened receptacle of the control and those of the APG fruits (comprising 1,250 receptacle expressed sequence tags) did not show any statistically significant change. These results indicate that FaPG1 plays a central role in strawberry softening.
ISSN:0032-0889
1532-2548
1532-2548
DOI:10.1104/pp.109.138297