Expression **data** of Arabidopsis MAPKKs were obtained from PLEXdb (AT40), including following Arabidopsis tissues: inflorescence, petals, stamen, pedicels, sepals, carpels, pollen, seedling, root, leaf, shoot and pistil. As well as following Arabidopsis mutants: ap1-15, ap2-6, ap3-6, ag-12, clv3-7, lfy-12 and ufo-1. Mapped reads were uniquely applied to deeper analysis. Gene expression levels were quantified by RPKM (reads per kilobase of mRNA length per million of mapped reads). Expression **data** of MAPKK genes in rice (GSE27726), poplar (GSE30507) and maize (GSE27004) were also downloaded from NCBI GEO database. Microarray **data** of Arabidopsis under abiotic treatment were also obtained from NCBI GEO **data** (GSE5620-GSE5628) in our analysis. For RT-qPCR analyses, 2-week-old B. distachyon Bd21 plants grown in each box were used for harvesting root, stem, leaf, young caryopsis and seedling samples. For UV-B treatments analysis, two-week-old B. distachyon Bd21 plants were treated as described previously [71]. Plants were harvested for further analyses after treatment 1 h, 3 h, 6 h, 12 h and 24 h, respectively. The primer-sets were listed in Additional file 21.