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  • Author or Editor: Ann Powell x
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While seed priming (hydration in water or osmotic solutions followed by drying) enhances seed germination performance, the longevity of primed seeds in storage often is reduced. Postpriming treatments including a reduction in seed water content followed by incubation at 37 or 40 °C for 2 to 4 h can substantially restore potential longevity in tomato (Lycopersicon esculentum Mill.) seeds. These conditions might induce heat-shock proteins (hsp) that could be involved in the extension of seed longevity. The abundance of BiP (78 kD Binding Protein), hsp70 and class I small hsp in primed seeds subjected to postpriming treatments was examined to assess this possibility. BiP mRNA and protein amounts increased during postpriming heat treatments that extended longevity of tomato seeds. Treatment of primed seeds with the calcium ionophore calcimycin (A21387) enhanced BiP protein accumulation in the absence of heat treatment and also extended potential seed longevity. Changes in the abundance of hsp70 and class I small hsps were not consistently associated with potential seed longevity. Thus, enhanced BiP expression may contribute to the improved longevity of primed seeds following postpriming treatments.

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Higher plant inhibitors of fungal polygalacturonases are potential contributors to plant defense. To test this hypothesis we have raised antibodies against the `Bartlett' pear fruit polygalacturonase inhibitor (PGIP) and cloned a pear fruit PGIP cDNA. The pear PGIP cDNA was isolated by polymerase chain reactions based on our amino acid and nucleotide sequence information. Sequence analysis predicts a gene product of 34.5 kD with an isoelectric point of 6.02 in agreement with our biochemical data. Seven potential glycosylation sites are consistent with the glycoprotein character of these PGIPs. Southern blot analysis suggests the presence of 1 or 2 genes in the pear genome. Northern blot analysis indicates the presence of a transcript of 1.5 kb. Western blot analysis shows cross-reactivity of the anti-pear PGIP antibody to various dicot species as well as corn.

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