Analysis ofcis-regulatory elements involved in the activation of a member of chalcone synthase gene family (PsChs1) in pea

Cis-regulatory elements involved in the activation of the plant defense-related gene encoding chalcone synthase 1 (PsChs1) in pea (Pisum sativum L.) were examined by transient transfection, gel mobility shift assay andin vitro DNase I-footprinting analysis. Transient transfection assay revealed that a 61 bp DNA fragment spanning from –242 to –182 ofPsChs1 was required for the maximal promoter activity and possibly involved in the enhancement of elicitor-mediated activation. Nuclear isolate from elicitor-treated pea epicotyl tissues contained some factor(s) that specifically bound to this DNA fragment to form a complex with low mobility (LMC, low mobility complex) in gel mobility shift assay. DNase I-footprinting analysis of LMC revealed that among three protected regions detected in a 61 bp DNA fragment, two regions contained identical AT-rich sequence, TAAAATACT. Site directed mutation in either or both identical sequences, TAAAATACT to TGGAATACT, resulted in the reduction or loss in the ability to form LMC. Detailed analysis of 61 bp DNA fragment demonstrated that the region from –242 to –226 containing promoter-distal TAAAATACT motif was imperative for the maximal elicitor-mediated activation ofPsChs1.     

麻疯树苯丙氨酸解氨酶启动子的克隆和表达载体的构建

苯丙氨酸解氨酶（phenylalanine ammonia lyase, PAL）是苯丙烷类代谢途径的关键酶,催化苯丙氨酸转化为肉桂酸,促进黄酮、香豆素等次生代谢物的生成。本文根据已克隆的麻疯树苯丙氨酸解氨酶基因JcPAL的序列设计引物,通过DNA步移技术,克隆出长度为1 334 bp的JcPAL基因起始密码子上游序列。序列分析显示其不仅具备CAAT、TATA盒这些保守元件,而且包含多种胁迫诱导元件,特别是在序列中发现一些苯丙氨酸解氨酶特有的元件。为了鉴定JcPAL基因的启动子元件,分别将长度不同的5′端侧翼区缺失体定向插入载体pBI121中, 取代原有的CaMV35S启动子,构建了4个驱动报告基因GUS的植物表达载体。     

Mycobacterium tuberculosis FurA autoregulates its own expression

The furA-katG region of Mycobacterium tuberculosis, encoding a Fur-like protein and the catalase-peroxidase, is highly conserved among mycobacteria. Both genes are induced upon oxidative stress. In this work we analyzed the M. tuberculosis furA promoter region. DNA fragments were cloned upstream of the luciferase reporter gene, and promoter activity in Mycobacterium smegmatis was measured in both the presence and absence of oxidative stress. The shortest fragment containing an inducible promoter extends 45 bp upstream of furA. In this region, -35 and -10 promoter consensus sequences can be identified, as well as a 23-bp AT-rich sequence that is conserved in the nonpathogenic but closely related M. smegmatis. M. tuberculosis FurA was purified and found to bind upstream of furA by gel shift analysis. A ca. 30-bp DNA sequence, centered on the AT-rich region, was essential for FurA binding and protected by FurA in footprinting analysis. Peroxide treatment of FurA abolished DNA binding. Three different AT-rich sequences mutagenized by site-directed mutagenesis were constructed. In each mutant, both M. tuberculosis FurA binding in vitro and pfurA regulation upon oxidative-stress in M. smegmatis were abolished. Thus, pfurA is an oxidative stress-responsive promoter controlled by the FurA protein.