Benfey Lab

Control of the orientation of cell expansion during root development in A. thaliana : Role of the COBRA gene

Mutations in the COBRA gene strongly affect root elongation. The cobra phenotype is characterized by a very short and thick root, making it look like an hostile Naja. The conditional nature of cob can be seen in the lateral root, which has grown into the 4.5% agar, thereby slowing down its growth rate.

In wild type plants, the cells generated in the meristem transiently expand in the radial axis after a limited isotropic expansion. This transient radial expansion is then shifted to the longitudinal axis and account for a big part of the root elongation. In cob the reorientation of expansion does not happen and cells continue to expand radially. The cobra mutations affect all the cell layers but the abnormal lateral expansion is most apparent in the epidermis.

COBRA encodes a membrane protein likely anchored on the external surface by a GPI moiety. The role of COBRA in the control of the orientation of cell expansion is currently under investigation via molecular, genetic, genomic and proteomic approaches.

References :

Roudier F., Schindelman G,, DeSalle R. and Benfey P. N.(2002). The COBRA
family of putative GPI-anchored proteins in Arabidopsis : a new
fellowship in expansion? Plant Physiology, 130: 538-48. [Abstract]

Benfey PN, Linstead PJ, Roberts K, Schiefelbein JW, Hauser MT, Aeschbacher RA. 1993. Root development in Arabidopsis: four mutants with dramatically altered root morphogenesis. 119: 57-70. [Abstract]

Hauser M.T., Morikami A. and Benfey P.N. 1995. Conditional root expansion mutants of Arabidopsis. Development 121: 1237-52. [Abstract]

Schindelman G., Morikami A., Jung J., Baskin T.I., Carpita N.C., Derbyshire P., McCann M.C. and Benfey P.N. 2001. COBRA encodes a putative GPI-anchored protein, which is polarly localized and necessary for oriented cell expansion in Arabidopsis. Genes Dev. 15: 1115-27. [Abstract]

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