Articles
MOLECULAR BIOLOGY OF POME FRUIT RIPENING AND SENESCENCE: CONCEPTS, STATUS, PERSPECTIVES AND FUTURE PROSPECTS
In 1969 the First International Symposium on this topic was held at the Research Station at Gorsem in Sint-Truiden, Belgium.
The Proceedings of that meeting make interesting and retrospective reading (Clijsters, 1969). Concepts newly emerging at that time were: pome fruit ripening is dependent upon ethylene and de novo protein synthesis; enzyme activities of ripening derive from a process of biochemical differentiation involving directed protein synthesis; methionine is the precursor for ethylene biosynthesis; ethylene action in ripening involves binding to a receptor, requires O2 and is competitively inhibited by CO2; mitochondrial oxidative phosphorylation remains fully competent over the course of ripening; mutants could be used to study ripening of tomato;
-farnesene may be involved in the scald disorder; and calcium may play a biochemical role in reducing bitterpit of apples.Polyacrylamide gel electrophoresis (PAGE) was then a new technique to separate proteins. Arabidopsis thaliana was still just a weed.
Endonucleases (restriction enzymes) were yet to be discovered.
Molecular biology was embryonic and genetic engineering was only a dream.
Several of the hypotheses raised at the 1969 symposium have now been tested and proven with surgical precision.
Conclusions of molecular experiments can be stated without equivocation as witnessed weekly in scientific journals world-wide.
The enzymes of ethylene biosynthesis, ACC synthase and ACC oxidase, have been identified, purified, cloned, characterized and antibodies developed for analytical reagents.
Gene expression studies reveal that development of the ethylene biosynthetic pathway is transcriptionally regulated through the expression of their respective mRNAs and this process is activated by ethylene.
Transgenic tomato plants have been developed by genetic engineering in which endopolygalacturonase and ethylene biosynthesis has been attenuated and, as a consequence, fruit ripening is delayed.
The evolution of molecular biological techniques and experimentation has heralded a renaissance of opportunities to understand and control fruit ripening.