Cloning, mapping and expression analysis of barley MADS-box genes

Six MADS-box cDNA clones were isolated by heterologous screening from a bar ley inflorescence cDNA library. Based on sequence comparison to known MADS- box genes, the barley MADS-box (BM) genes were grouped into three distinct phylogenetic subclasses of the MADS-box gene family. The three MADS-box gen es BM3, BM5 and BM8 share similarities with genes of the SQUAMOSA (SQUA) su bgroup, while BM7 and BM9 belong to the AGAMOUS-LIKE 2 (AGL2) subgroup. BM1 resembles MADS-box genes described as solitary sequences or orphan genes. Expression analysis of the barley MADS-box genes revealed expression patter ns that are not characteristic of the barley MADS-box genes of the SQUA sub group, while expression of BM7 and BM9 was largely as expected for the AGL2 subgroup. BM1 is mainly expressed in vegetative tissues and its primary tr anscript undergoes alternative splicing such that the corresponding mRNAs d iffer by two codons. The genes BM1, BM3 and BM8 were mapped by analysis of single-nucleotide polymorphisms onto barley chromosomes 4, 2 and 7, respect ively.