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Previously my group was involved for many years in understanding seed development of peas as it relates to storage product deposition. In this work, we make use of a number of mutants that affect embryo development and that affect the synthesis of starch, all of which were generated through a mutation programme started in 1987. We used the r isolines to develop the model shown here (the so-called Jigsaw model) of the way the lesion in starch synthesis affected the development of the seed. Based on this model we screened EMS mutagenised seed for the wrinkled-seeded character and isolated a number of pea mutants. Complementation analysis revealed the mutants fell into five groups, two of which were the existing r and rb loci, and the other three were subsequently named rug3, rug4 and rug5. Further screening in collaboration with Alison Smith and Kay Denyer, using the colour of iodine-stained starch grains, led to the isolation of mutants at a sixth locus, low amylose (lam).

 

The genes at each locus have been identified and each the mutants characterised. All of the genes encode enzymes in the pathway of starch biosynthesis. We now have a range of material in an isogenic background with starch contents from 1-50% of the embryo dry weight and with amylose contents from 15-75% of the starch content (measured chemically).

We have carried out an extensive study of embryo development in peas using mutants, conventional histology, cell separation techniques, immunochemistry, and in situ RNA hybridisation. Embryo mutants were isolated by screening young embryos in their seeds.

 

Historically I have always had an interest in plant hormones, especially cytokinins. More recently I have used a model system, the moss Physcomitrella patens, to investigate their action. If you want to know more about P. patens as a model plant for gene targeting click here.