Two different cDNA clones (Sscat1 and Sscat2) encoding catalase, the primary important H2O2_scavenging enzyme, were isolated from a λZap_cDNA library constructed from a 400 mmol/L NaCl_treated library of Suaeda salsa (L.) Pall aerial tissue. Sscat1 (1.7 kb) contains a full open reading frame of 492 amino acids and Sscat2 (1.1 kb) is a partial clone. BLAST analysis indicates that the two clones share 71.9% identity in nucleotide sequence and 75% identity in deduced amino acid sequence within the last 287 amino acid residues of Sscat1. Southern blotting analysis showed that Sscat1 is multicopy in S. salsa genome, while Sscat2 is a single copy gene. Northern blotting analysis showed a rapid increase in the steady_level of both genes in roots after 48 h salt treatment, but only Sscat1 was induced in salinity treated leaves. Time_course analysis carried out in leaves confirmed that Sscat1 was induced by salt stress, in contrast to Sscat2. These implied that the expression of Sscat1 and Sscat2 genes are differentially regulated in S. salsa. The activity of total catalase is dramatically increased in response to salt stress.
摘要：过氧化氢酶是清除H2O2的重要酶类，从400mmol/LNaCl处理的盐地碱蓬（Suaeda salsa(L.)Pall)地上部分的cDNA文库中克隆了两个编码过氧化氢酶的cDNA(Sscat1和Sscat2)。其中Sscatl(1.7kb)是一个全长cDNA克隆，编码一个492个氨基酸的开放阅读框架。而Sscat2(1.1kb)是一个cDNA片段。据编码Sscatl3′端的287个氨基酸的cDNA序列与Sscat2的cDNA序列进行的BLAST同源性分析表明，Sscat1和Sscat2在核苷酸水平的一致性则为一个单拷贝基因。Northern杂交结果表明在盐胁迫条件下Sscat1和Sscat2的表达存在差异；400mmol/LNaCl处理48h的盐地碱蓬根中的Sscat1和Sscat2mRNA水平比对照显著提高，但是在叶中仅Sscat1受盐诱导表达，不同盐处理时间下的表达分析也证实。在盐地碱蓬叶中仅Sscat1受盐诱导表达。这说明Sscat1和Sscat2在盐地碱蓬中是差异调控的，生理分析表明过氧化氢酶的活性在盐胁迫条件下显著提高。
关键词：盐地碱蓬,过氧化氢酶,盐胁迫,表达分析,活性氧,基因克隆
