Novel function of a putative MOC1 ortholog associated with spikelet number per spike in common wheat

Axillary meristems play an important role in determining final plant architecture and floral structures. Tomato Ls, Arabidopsis LAS and rice MOC1 are orthologous genes regulating axillary meristem initiation and outgrowth. Their functions are generally conserved but the functional specificities are divergent among species. Obvious differences between rice panicles and wheat spikes suggest the divergent functions of MOC1 and its wheat ortholog. We show that TaMOC1 might be involved in wheat spikelet development. TaMOC1 is a typical nucleus localized protein with transcriptional activation abilities. The variable N-termini of TaMOC1 protein is necessary for transcriptional activation. TaMOC1 is highly expressed in ears with length of 2, 3 and 6 cm. Significant associations between the TaMOC1-7A haplotype and spikelet number per spike were observed in ten environments over 3 years and 2 sites. TaMOC1-7A HapH, a favored haplotype acquired during wheat polyploidization, may make a positive contribution to spikelet number per spike. Based on evolutionary analysis, geographic distribution and frequency changes, TaMOC1-7A HapH might be associated with wheat domestication and Chinese wheat breeding history. The pyramiding favorable alleles of TaMOC1-7A HapH and TaSnRK2.10 (C, associated with higher TGW) can improve both spikelet number per spike and TGW simultaneously.