水稻白叶枯病菌对拌种灵抗药性分子机制研究

  通过紫外诱变获得了抗拌种灵水稻白叶枯病菌（Xanthomonas oryzae pv.oryzae）的突变体，这些突变体可以在含100 μg·ml-1拌种灵平板上生长，而敏感菌株在10 μg·ml-1浓度下则不能生长。敏感菌株琥珀酸脱氢酶活性受拌种灵强烈抑制，而抗药突变体的酶活性较低，且不受药剂抑制。应用6对引物，从水稻白叶枯病菌野生敏感菌株和室内诱导抗药性菌株中扩增到琥珀酸脱氢酶基因全序列。该基因全长3 616 bp，编码1 115个氨基酸，含有2个内含子。与柑橘溃疡病菌（Xanthomonas axonopodis pv. citri）琥珀酸脱氢酶核苷酸同源性93%，氨基酸同源性97%；与其它6种病原细菌琥珀酸脱氢酶基因编码的氨基酸序列同源性为43%～95%。敏感菌株和抗药菌株的琥珀酸脱氢酶序列分析表明，琥珀酸脱氢酶铁硫蛋白亚基中229位氨基酸由组氨酸（CAC）突变为酪氨酸（TAC）是导致X. oryzae对拌种灵产生抗药性的主要原因。

Molecular Mechanism of Amicarthiazol Resistance in Xanthomonas oryzae pv.oryzae

The resistance mutants of wild-type Xanthomonas oryzae pv.oryzae to amicarthiazol were got by ultraviolet(UV) irradiation in laboratory. These mutants could grow in the medium containing 100 μg·ml-1 of amicarthiaol. However the wild-type sensitive strain could not grow at 10 μg·ml-1. The activity of succinate dehydrogenase(SDH) was strongly inhibited by amicarthiazol while the activity of SDH from resistant mutants was very low and was not inhibited by the chemical. Six pairs of special primer based on the conserved region of Xanthomonas axonopodis pv.citri were designed and used to amplify the gene encoding succinate dehydrogenase from X.oryzae. Whole gene of succinate dehydrogenase has 3 616bp, 1 115 deduced amino acids and two introns. The homology of the nucleotide sequence and deduced amino acid of X. oryzae with that of X.citri was 93% and 97% respectively. Compared with that of other six bacteria, the homology of deduced amino acid of succinate dehydrogenase was from 43% to 95% respectively. Sequence comparison among sensitive and five mutants revealed that mutant gene encodes a modified iron-sulpher subunit of succinate dehydrogenase with a amino-acid substitution (His 229→Tyr).