Fig. 2

Histidine kinases in Medicago truncatula. a Number of genes encoding HKs found in the genome of A. thaliana, M. truncatula and V. vinifera. b Phylogenetic tree of HKs, based on full-length protein sequences from A. thaliana, M. truncatula and V. vinifera. Protein sequences were aligned with the Muscle algorithm and the phylogenic tree was built with the Seaview software package. Numbers indicate the probability for each branch. Proteins labelled with a blue dot are non-canonical HKs. c Heat map of the expression pattern of M. truncatula genes encoding HK proteins. Data were retrieved from the M. truncatula Gene Expression Atlas Affymetrix microarray database (MtGEA; [68]) for various organs (left panel), from [69] for roots, nodules and nodule zones (middle panels) and from [60] for root epidermis expression and response to Nod factors (NF, right panel). Meristematic zone (ZI), distal and proximal differentiation/rhizobial infection zones (ZIId and ZIIp), inter-zone (IZ) and nitrogen fixation zone (ZIII). The red/white color scale indicates log2 expression values for each heat map, which were normalized independently, with highest expression as red and lowest expression as white. A median was used as the central value and black boxes indicate that no probe was available on the microarray