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Regulator of cell reprogramming

Plant ontogeny (formation of an individual plant body) starts with a pattern formation in embryogenesis. Plants in the Brassica family, including the model plant species Arabidopsis thaliana, exhibit a notablly regular pattern formation in very early stages of embryogenesis. For such a patterning process to be initiated, plant cells need to be reprogrammed to activate embryo-specific genes. We identified a gene that is capable of reprogramming somtic plant cells to embryonic status. We are currently investigating the mechanisms by which this gene reprograms somatic cells.

 

We have identified mutants that exhibited abnormally enhanced cell division capacity in the root, by using the activation tagging strategy mentioned in the previous page.This abnormality was caused by the overexpression of members of the poorly characterized RKD gene family. After a number of trials, we could finally identified RKD4, a member of the gene family, as a key regulator of embryogenesis and reprogramming.

Interestingly, ectopic expression of RKD4 in seedlings resulted in formation of the callus-like cell mass. When RKD4 overexpression was terminated thereafter, numerous embryos form from the cell mass. There are only few example of such drastic changes in cell status caused by the overexpression of a single gene. We are interested in the mechanism by which RKD4 promotes cell reprogramming and embryogenesis.

Genes homologous to RKD4 exist in all sequenced plant genomes. We are also trying to translate this gene function to efficient propagation of commercially imporant plants.

Reference:
Waki, et al. (2011). "The Arabidopsis RWP-RK protein RKD4 triggers gene expression and pattern formation in early embryogenesis." Curr. Biol. 21, 1277-1281. PubMed Publisher Press