JXB Advance Access published online on June 2, 2008
Journal of Experimental Botany, doi:10.1093/jxb/ern142
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© 2008 The Author(s).
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
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RESEARCH PAPER |
Antisense inhibition of a pectate lyase gene supports a role for pectin depolymerization in strawberry fruit softening
1Departamento de Biología Vegetal, Facultad de Ciencias, Universidad de Málaga, Campus de Teatinos s/n, 29071 Málaga, Spain
2Department of Plant Biology, Cornell University, Ithaca, NY 14850, USA
3Departamento de Bioquímica y Biología Molecular, Universidad de Córdoba, 14071 Córdoba, Spain
* To whom correspondence should be addressed. E-mail: quefe{at}uma.es
Cell wall disassembly in softening fruits is a complex process involving the cumulative action of many families of wall-modifying proteins on interconnected polysaccharide matrices. One strategy to elucidate the in vivo substrates of specific enzymes and their relative importance and contribution to wall modification is to suppress their expression in transgenic fruit. It has been reported previously that inhibiting the expression of pectate lyase genes by antisense technology in strawberry (Fragariaxananassa Duch.) fruit resulted in prolonged fruit firmness. This suggested that pectin depolymerization might make a more important contribution to strawberry fruit softening than is often stated. In this present study, three independent transgenic lines were identified exhibiting a greater than 90% reduction in pectate lyase transcript abundance. Analyses of sequential cell wall extracts from the transgenic and control fruit collectively showed clear quantitative and qualitative differences in the extractability and molecular masses of populations of pectin polymers. Wall extracts from transgenic fruits showed a reduction in pectin solubility and decreased depolymerization of more tightly bound polyuronides. Additional patterns of differential extraction of other wall-associated pectin subclasses were apparent, particularly in the sodium carbonate- and chelator-soluble polymers. In addition, microscopic studies revealed that the typical ripening-associated loss of cell–cell adhesion was substantially reduced in the transgenic fruits. These results indicate that pectate lyase plays an important degradative role in the primary wall and middle lamella in ripening strawberry fruit, and should be included in synergistic models of cell wall disassembly.
Key words: Cell wall, Fragaria, fruit ripening, pectate lyase, pectinases, strawberry
Received 25 January 2008; Revised 20 April 2008 Accepted 21 April 2008
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