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At least 325 records · Page 18Linked to original sources
PubMed2004

Targeted modification of homogalacturonan by transgenic expression of a fungal polygalacturonase alters plant growth.

Pectins are a highly complex family of cell wall polysaccharides comprised of homogalacturonan (HGA), rhamnogalacturonan I and rhamnogalacturonan II. We have specifically modified HGA in both tobacco (Nicotiana tabacum) and Arabidopsis by expressing the endopolygalacturonase II of Aspergillus niger (AnPGII). Cell walls of transgenic tobacco plants showed a 25% reduction in GalUA content as compared with the wild type and a reduced content of deesterified HGA as detected by antibody labeling. Neutral sugars remained unchanged apart from a slight increase of Rha, Ara, and Gal. Both transgenic tobacco and Arabidopsis were dwarfed, indicating that unesterified HGA is a critical factor for plant cell growth. The dwarf phenotypes were associated with AnPGII activity as demonstrated by the observation that the mutant phenotype of tobacco was completely reverted by crossing the dwarfed plants with plants expressing PGIP2, a strong inhibitor of AnPGII. The mutant phenotype in Arabidopsis did not appear when transformation was performed with a gene encoding AnPGII inactivated by site directed mutagenesis.

Arabidopsis↗
PubMed1995

The extreme C-terminus is required for secretion of both the native polygalacturonase (PehA) and PehA-Bla hybrid proteins in Erwinia carotovora subsp. carotovora.

A set of gene fusions was constructed between the pehA gene encoding the secreted endopolygalacturonase (PehA) and the bla gene coding for a normally periplasmic beta-lactamase (Bla). The resulting hybrid proteins were specifically and actively routed out of the cells via the Out-terminal branch of the general secretory pathway (GSP) in Erwinia carotovora subsp. carotovora (Ecc), provided that no more than the last two amino acids (aa) of the PehA domain were excluded from the fusion. However, both PehA-Bla hybrid proteins and PehA variants lacking at least four aa from the C-terminus of the PehA accumulated in the periplasm. Also, overexpression of the gene fusions prevented extracellular targeting of the hybrid proteins. Site-directed mutagenesis of the codons -4 and -3 (encoding Asn-373 and Val-374, respectively) from the end of the pehA gene and analysis of the protein products suggested that the Val-374 was important both for the structure and secretion of PehA, while the Asn-373 proved to be insignificant. We conclude that: (i) the GSP of Ecc is capable of secreting heterologous proteins; (ii) as the PehA protein can accommodate C-terminal extensions, secretion can occur with no part of the proposed targeting signal lying within the C-terminal extremity of a secreted molecule; and (iii) residues within the C-terminus of PehA play a role in secretion, possibly through stabilization of a structure needed for proper exposition of the proposed targeting motif.

Amino Acid Sequence↗
PubMedDate not supplied

[Effect of proteinaceous polygalacturonase inhibitors from apple seed tissue on an enzyme isolated from phytopathogenic fungi].

A protein polygalacturonidase inhibitor isolated from fruit of the apple varieties Antonovka and Mantuanskoe differently affects the polygalacturonidases of different phytopathogenic fungi. Three groups of fungi were recognized by the sensitivity of their polygalacturonidases to the inhibitory effect. Storage of apples after harvesting is accompanied by changes in the inhibitor activity, and the time pattern of these changes depends on the variety. An increase in the inhibitor activity occurs concurrently with the elevation in ethylene release characteristic of the stage of elevated respiration (a climacteric increase). The data suggest that a decrease in the apple fruit resistance to microbes at the end of the storage period is related, along with other reasons, to a change in the activity of the protein polygalacturonidase inhibitor.

Enzyme Inhibitors↗