Characterisation of novel plant genes encoding MEKK/STE11 and RAF-related protein kinases

Various elements of the MAP kinase module have been isolated in plants. We describe here the characterisation of 14 new plant cDNAs and genes encoding putative MAP kinase kinase kinases (MAP3Ks) related to the MEKK/STE11 and RAF protein kinases. Plant MAP3Ks are characterised by a variety of primary structures conserved within closely related proteins. Southern blot analys is suggests that plant MAP3Ks are heterogenous in their genomic structure, existing either as single copy genes or as small gene families. An RT-PCR a nalysis showed that in Arabidopsis thaliana, all organs studied contain det ectable levels of transcripts of each of the MAP3K genes identified; howeve r, signals obtained with mature pollen were weak or non-existent except for AtMAP3K gamma. None of the reported genes share a cell-cycle or a cold str ess regulated expression. (C) 1999 Elsevier Science B.V. All rights reserve d.