Phylogeny, chromosomal mapping and expression analyses of wheat CLAVATA pathway components suggest differential selection on receptor-like kinases, CLEs and T3 WOXes.

Ensuring continuous global food security is a major challenge of the 21st century. Wheat contributes approximately 20% of the total calories consumed by humans, and an estimated 60% increase in production will be required by 2050 to meet forecast global demand. In cereals like wheat, inflorescence (ear) size and branching patterns determine the number of flowers (florets) and grains produced, and these aspects of plant architecture are regulated by the activity of stem cells in the growing shoot tips. CLAVATA peptide and receptor-like kinase signalling regulates angiosperm stem cell activity, and as changes in CLAVATA function can improve crop yields, CLAVATA is a key target for reverse engineering. Here, we identify components of the wheat CLAVATA pathway using genome searches against Triticum aestivum and its wild relatives Triticum turgidum ssp. durum, Triticum turgidum ssp. dicoccoides, Triticum urartu and Aegilops tauschii. Using phylogenetic and synteny analysis, we determine the relationship between homoeologues and infer patterns of gene family evolution. Whilst CLAVATA1, BARELY ANY MERISTEM, RECEPTOR-LIKE PROTEIN KINASE 2, CORYNE and CLAVATA2 receptor-like kinase homologues are mainly present as single genome copies as in other grasses, CLAVATA3-like but not TRACHEARY ELEMENT DIFFERENTIATION FACTOR (TDIF)-like peptide encoding genes and WUSCHEL-LIKE HOMEOBOX (WOX) genes have expanded copy numbers with many gene gains and losses during evolution. Our results highlight wheat CLAVATA pathway components for reverse genetic analysis and indicate potential differential selection on wheat receptor-like kinases, their peptide ligands and WOXes.