Auxin takes root( As published in the December 1st issu...)

As published in the December 1st issue of Genes & Development, Dr. Nam-Hai Chua and his team at Rockefeller University in New York have begun to unravel the molecular mechanisms by which plants develop roots. Roots are formed during embryonic development, and provide stability and a means of nutrient absorbtion during the life of the plant. The plant hormone, auxin, has been linked to root formation, but the actual pathway of its action has, until recently, remained a mystery.

Dr. Chua and colleagues began their investigation of the auxin signaling pathway with a novel plant gene called NAC1. NAC1 shows no similarity to any known gene in animals or yeast, so its function was totally unknown. To gain insight into the function of NAC1, Dr. Chua and colleagues investigated the expression and activity patterns of the NAC1 protein. The scientists found that NAC1 is expressed in the root tips, and that switching the gene on or off increased or reduced the number of emerging roots, respectively. Furthermore, they found that NAC1 functions in the nucleus by binding to DNA. Using these insights, the team was able to identify NAC1 as a classical gene regulator. Dr. Chua and colleagues then went on to discover two targets of NAC1, both of which had already been shown to be responsive to auxin signaling. However, a question still remained as to what regulates NAC1.

Finally, NAC1 was linked to the auxin pathway by demonstrating that NAC1 is regulated by auxin, and that the effect of auxin on root formation is mediated by NAC1. NAC1 can even compensate for the lack of another gene, tir1, which has previously been established as a mediator of auxin signaling. This is the first study to define a role for Nac1 in root development. The strides which Dr. Chua and his colleagues have made in delineating the pathway of auxin signaling represents a tremendous advance in the understanding of the molecular pathway of root development.

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Contact: Nora Poppito
poppito@cshl.org
Cold Spring Harbor Laboratory
30-Nov-2000