Anthony Cashmore

In 1881, Francis Darwin and Charles Darwin demonstrated that plants exhibited a phototropic response to blue light.

Elusive to discovery, scientists gave the name cryptochrome to the photoreceptor factor(s) responsible for this effect.

Anthony R. Cashmore (b. 22 Jan 1941) is a biochemist and plant molecular biologist, best known for identifying cryptochrome photoreceptor proteins.

These specialized proteins are critical for plant development and play an essential role in circadian rhythms of plants and animals.

Born in Auckland (New Zealand) in 1941, Cashmore grew up in Manawaru and Te Aroha.

As a teenager, Cashmore worked in Palmerston North in the Grasslands Division of New Zealand's Department of Scientific and Industrial Research (DSIR).

Cashmore enrolled at the University of Auckland, majoring in chemistry and completing a Bachelor of Science degree in 1962, Master of Science degree in 1963, and Ph.D. degree in 1966.

In 1968 Cashmore moved to Cambridge (UK) to pursue postdoctoral studies at the University of Cambridge Department of Chemistry, and later at the MRC Laboratory of Molecular Biology.

In 1971 Cashmore moved to the United States, where he worked as a Research Associate in the laboratory of Michael Chamberlin at the University of California, Berkeley before returning to New Zealand.

In 1979, Cashmore took a position at the Rockefeller University (New York), first as a visiting scientist in the laboratory of Nam-Hai Chua, and then as an assistant professor, then Associate Professor.

Interested in adopting the "power of Arabidopsis genetics" for the study of light regulation, in 1980 Cashmore, working with post-doctoral student Margaret Ahmad, identified Arabidopsis mutants that showed reduced sensitivity to blue light.

Using DNA sequencing and complementation techniques, Cashmore and Ahmed cloned the gene and discovered that the mutants were alleles of a previously identified hy4 mutant.

Ahmad and Cashmore called this blue light photoreceptor "cryptochrome", and it is now referred to as CRY1.

Cashmore's research group identified a second member of the cryptochrome family (CRY2) using cDNA library screening.

This research was the foundation that led to the identification of CRY proteins in other plant species, bacteria, fungi, animals, and humans, as well as research that defined the pivotal role of these proteins in circadian clock regulation across species and as the primary sensory molecule enabling light-dependent magnetic compass orientation in migratory birds.

Today, light-based diagnostic and therapeutic wearable photonic healthcare devices, are based on the function of the cryptochrome photoreceptors.

A Professor emeritus in the Department of Biology at the University of Pennsylvania, Cashmore led the Plant Science Institute from the time of his appointment in 1986 until his retirement in 2011.

In 1986, Cashmore was appointed the Director of the Plant Science Institute at the University of Pennsylvania (Philadelphia).

He was elected to the National Academy of Sciences in 2003.

He retired in 2011 and is currently an Emeritus Professor of Biology at the University of Pennsylvania.

During his PhD studies, Cashmore purified the toxic component of Pimelea prostrata, a New Zealand toxic shrub.

Using partition chromatography, Cashmore purified and crystallized the active component, referred to as prostratin.

Cashmore's studies showed that prostratin was strikingly similar to the co-carcinogenic phorbol esters of croton oil, a relationship that was subsequently confirmed using chemical synthesis and x-ray crystallography approaches.

Working with George Petersen (a New Zealand biochemist) at New Zealand's Department of Scientific and Industrial Research (DSIR) (Palmerston North), Cashmore was introduced to the study of nucleic acids and how selective chemical reagents could be used to determine the nucleic acid sequence of DNA.

Cashmore and Petersen examined the use of hydrazine as a tool to measure purine nucleotides in samples of DNA.

Recognizing that hydrazine-treated DNA subsequently exposed to alkali conditions undergoes degradation, Cashmore defined a quantitative technique for measuring purine nucleotides in DNA samples.

Subsequently, Allan Maxam and Walter Gilbert employed the hydrazine degradation approach to develop Maxam–Gilbert sequencing, the first widely adopted method for DNA sequencing.

Working with Dan Brown at Cambridge University, Cashmore demonstrated that the reagent methoxyamine reacted with a limited number of cytosine residues in tRNA.

Later, Cashmore used the RNA sequencing procedure that had recently been developed by Fred Sanger to identify the reactive cytosine residues in a tyrosine suppressor tRNA of Escherichia coli.

Studying a mutant of this tRNA, Cashmore identified a new reactive cytosine residue at the base of loop III.

This finding suggested that base pairing of conserved residues occurred supporting one of the early models proposed for the three dimensional structure of transfer RNA.

Ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO), thought to be the world's most abundant protein, utilizes photosynthetic energy to fix carbon dioxide through the conversion of ribulose-1,5-bisphosphate to two molecules of 3-phosphoglycerate.

It is an enzyme of interest in the field of climate change due to its role in fixing carbon dioxide.

At New Zealand's DSIR Palmerston North, Cashmore studied the biosynthesis of RuBisCO, a multi-subunit (eight large and eight small subunits) protein located in plant chloroplasts.

Using selective inhibitors of protein synthesis Cashmore showed that in contrast to the RuBisCO large subunit (which was known to be synthesized on chloroplast ribosomes), the small subunit of RuBisCO was produced as a soluble precursor protein on cytoplasmic ribosomes.

The soluble precursor protein is subsequently processed and imported into chloroplasts.

At Rockefeller University, Cashmore studied DNA sequences associated with light regulated expression of a pea nuclear RuBisCO small subunit gene.

For these studies, Cashmore collaborated with scientists in the laboratory of Jeff Schell and Marc Van Montagu in Ghent (Belgium).

Using transgenic plant cells, they demonstrated that in the pea plant, light-regulated expression was mediated by a 1 kilobase (kb) promoter fragment.

In a second study, this DNA fragment was shown to have the properties of an enhancer sequence, functioning in either orientation and when fused to a normally non-light-regulated promoter.