Cellulase gene expression in ripening avocado fruit: The accumulation of cellulase mRNA and protein as demonstrated by cDNA hybridization and immunodetection

Summary A cDNA library was constructed from poly(A)⁺RNA of ripe avocado fruit. Colony hybridization identified a number of ripening specific clones of which one, pAV5, was shown to be specific for cellulase. Hybrid selection with pAV5 provided a message from ripe fruit that on in vitro translation yielded a polypeptide of 53kD, comigrating with purified avocado cellulase on SDS polyacrylamide gel electrophoresis. The translation product was selectively immunoprecipitated by antiserum to purified avocado cellulase. Immunoblotting of unripe and ripe avocado fruit extracts following SDS-PAGE showed a plentiful immunoreactive polypeptide in ripe fruit, and essentially none in unripe fruit. Hybridization of pAV5 to poly(A)⁺-RNA from unripe and ripe avocado fruit demonstrated that there is at least a 50-fold increase in the cellulase message concentration during ripening. Thus, the expression of cellulase enzyme activity during ripening is regulated by the appearance of mRNA coding for cellulase rather than by either translational or post-translational control mechanisms.Abbreviations poly(A)⁺ polyadenylated - DS sodium dodecyl sulfate - D kilodalton - bp base pairs Supported by Research Grant GM 19807 from the United States Public Health Service and by additional funds from the University of California Research Council.     

Isolation and characterisation of cDNA clones for tomato polygalacturonase and other ripening-related proteins

Summary Gene expression during the ripening of tomato fruit was investigated by cDNA cloning and hybrid-select translation. A cDNA library was prepared from poly(A)-containing mRNA from ripe tomato fruit and sreened by differential hybridization. 146 ripening-related cDNA clones were found. Eleven groups and eight unique clones have been identified so far. The sizes of the cloned cDNA inserts were determined and type-members for seven groups were used in hybrid selection experiments. Six of the seven clones encode translation products corresponding to six ripening related polypeptides detected previously by in vitro translation of total cytoplasmic RNA (14). One cDNA group codes for a M_r 48 000 protein that was identified as polygalacturonase on the basis of immunoprecipitation with specific antiserum raised against tomato polygalacturonase. re]19840918 rv]19850613 ac]19850618     

Two classes of differentially regulated glutamine synthetase genes are expressed in the soybean nodule: a nodule-specific class and a constitutively expressed class

We have characterized two sets of cDNA clones representing the glutamine synthetase (GS) mRNA in soybean nodules. Using the 3-untranslated regions of a representative member of each set, as gene member(s) specific probes, we have shown that one set of the GS genes are expressed in a nodule-specific manner, while the other set is expressed in other tissues, besides the nodules. The nodule-specific GS genes are expressed in a developmentally regulated manner in the nodules, independent of the onset of nitrogen fixation. The other class of GS genes is expressed constitutively in all tissues tested, but its expression level is dramatically enhanced in nodules following onset of N2 fixation. The latter set of genes is also expressed in cotyledons of germinating seedlings in a developmentally regulated manner. Analysis of hybrid select translation products and genomic Southern blots suggests that multiple gene members in each class are expressed in the nodules.