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R Sexton

Publications and source records attributed to R Sexton.

32 records · Page 2Linked to original sources
PubMed1988

Bean abscission cellulase : characterization of a cDNA clone and regulation of gene expression by ethylene and auxin.

The physiology and anatomy of abscission has been studied in considerable detail; however, information on the regulation of gene expression in abscission has been limited because of a lack of probes for specific genes. We have identified and sequenced a 595 nucleotide bean (Phaseolus vulgaris cv Red Kidney) abscission cellulase cDNA clone (pBACl). The bean cellulase cDNA has extensive nucleic and amino acid sequence identity with the avocado cellulase cDNA pAV363. The 2.0 kilobase bean mRNA complementary to pBACl codes for a polypeptide of approximately 51 kilodalton (shown by hybrid-selection followed by in vitro translation). Bean cellulase antiserum is shown to immunoprecipitate a 51 kilodalton polypeptide from the in vitro translation products of abscission zone poly(A)(+) RNA. Ethylene initiates bean leaf abscission and tissue-specific expression of cellulase mRNA. If ethylene treatment of bean explants was discontinued after 31 h and then 2,5-norbornadiene given to inhibit responses resulting from endogenously synthesized ethylene, polysomal cellulase mRNA hybridizing to pBACl decreased. Thus, ethylene is required not only to initiate abscission and cellulase gene expression but also to maintain continued accumulation of cellulase mRNA. Explants treated with auxin 4 hours prior to a 48 hour treatment with ethylene showed no substantial accumulation of RNA hybridizing to pBACl or expression of cellulase activity.

Journal Article↗
PubMed1984

Polarity, calcium and abscission: molecular bases for developmental plasticity in plants.

This article considers novel aspects to plant development. It starts by outlining the concept of plastic development. It then discusses polarity in plants arguing for the vascular tissue and surrounding cells as a major internal polar axis. The requirement for a change in polarity in this system when regeneration occurs is discussed and molecular mechanisms for specification and changing of polarity are outlined. The process of abscission is then discussed as an example of plastic development and it is concluded that many factors control abscission. Molecular changes in abscission zone cellulase are summarized and the notion of two phases in abscission are developed and generalized to other systems of development in plants.

Calcium↗