[Cloning and expression analysis of drought-tolerant and wa-ter-saving related gene PmMYB in broomcorn millet]

Exploring novel genes and gene combinations are of primary importance in plant drought-tolerance and water-saving research. Based on the EST sequence of MYB gene obtained in the research on molecular basis of drought-tolerance and water-saving in broomcorn millet (Panicum miliaceum L.), a 1 739 bp genomic sequence of MYB gene, designated PmMYB, was amplified using primers based on this EST sequence and that of rice MYB18. Sequence analysis indicated that PmMYB consisted of 2 introns, 121 bp (347-467 bp) and 93 bp (599-691 bp) in length respectively, and 3 extrons. The full-length cDNA sequence of PmMYB is 1 525 bp, which includes 212 bp 3' untranslated region, 41 bp 5' untranslated region, and 1 272 bp coding region which encodes 424 amino acids with a serine-rich region. PmMYB is a typical R2, R3-MYB transcription factor with its 2 typical DNA-binding domains (amino acid sites of 13-63 and 66-114). The multiple alignment of R2, R3 amino acid repeat regions of MYB genes among broomcorn millet, rice, corn, loblolly pine, Arabidopsis, capsicum, upland cotton, barley and aubergine indicates that R2, R3 repeat regions are very conserved. The phylogenetic analysis based on amino acid sequence shows that MYB genes are highly divergent with similarity ranging from 32% to 84%. PmMYB has the highest similarity (84%) with MYB18 gene of rice, whereas 46% and 41% with barley and corn, respectively. Semi-quantitative RT-PCR confirmed that PmMYB was upregulated by water stress and re-watering in broomcorn millet. Cloning this gene may provide a good foundation to improve the drought-tolerance and water-saving in broomcorn millet as well as in other plants.