Abstract: To explore more genes for the improvement of drought-tolerance and water use efficiency in plants, broomcorn millet (Panicum miliaceum L.) was used to investigate the differential gene expression during drought stress and re-watering after serious drought stress by constructing SSH-cDNA library in previous study. A full-length cDNA of S-adenosylmethionine synthetase (SAMS) gene was amplified from broomcorn millet using PCR. The PCR primers were designed based on an EST sequence highly similar to SAMS gene in the SSH-cDNA library and the sequences of SAMS genes from rice and barley. The full-length cDNA sequence of SAMS gene amplified from broomcorn millet was 1 293 bp in length and designated as PmSAMS, encoding 396 amino acids with the 3 typical domains of SAMS (N terminal domain, inter domain and C terminal domain). Multiple alignment analysis based on the amino acids encoded by some SAMS genes from broomcorn millet (P. miliaceum L.), potato (S. tuberosum), Arabidopsis (A. thaliana), sugar beet (B. vulgaris), barley (H. vulgare), litchi (L. chinensis), tomato (L. esculentum), and rice (O. sativa) indicated that SAMS was very conserved among different species of plants with 92–97% of sequence similarity of amino acids, and PmSAMS had the highest similarity with that of rice (97%). The expression patterns of PmSAMS during drought and re-watering after serious drought were investigated by means of semi-quantitative RT-PCR. The results showed that the ex-pressions of PmSAMS were great at the beginning of drought treatment (soil relative moisture of 36%), then declined under seri-ous drought (soil relative moisture of 24%) to less than the normal level, and increased at 2 h after re-watering, declined to the normal level at 6 h after re-watering. The expression patterns of PmSAMS during drought and re-watering after serious drought indicated that it was involved in the response of broomcorn millet to drought and re-watering and might be one of the key genes for drought tolerance and water use efficiency of broomcorn millet. The cloning of this gene provides the potential for its utiliza-tion in the improvement of drought-tolerance and water use efficiency in other plants.

Key words: Broomcorn millet, S-adenosylmethionine synthetase, Drought and re-watering, Express profile, Phylogenetic analysis