A MAPKKK in Embryonic Plant Cell Fate

Abstract

Lukowitz et al. screened Arabidopsis mutants for those with a defect in suspensor cell formation and identified a member of the mitogen-activated protein kinase kinase kinase (MAPKKK) family. Suspensor cells are one of the two cells that arise immediately after fertilization. The suspensor cell forms an extra-embryonic structure, whereas the apical cell goes on to form the embryo. Loss-of-function mutations in the YODA ( YDA ) gene, which the authors characterized as encoding a MAPKKK, produced plant embryos lacking a suspensor. The yda plants that did develop into mature plants exhibited delayed root development and were smaller than wild-type plants. Confirmation that kinase activity was essential came from analysis of yda mutants in the catalytic domain. In conclusion, none of the known plant hormones rescued the yda phenotype, which suggests a novel developmental signaling pathway. Benfey describes how these results reveal that plants and animals are more similar than previously appreciated. W. Lukowitz, A. Roeder, D. Parmenter, C. Somerville, A MAPKK kinase gene regulates extra-embryonic cell fate in Arabidopsis . Cell 116 , 109-119 (2004). [Online Journal] P. N. Benfey, A common switch used by plants and animals. Cell 116 , 4-5 (2004). [Online Journal]