CONSERVED MOTIFS IN A DIVERGENT NOD BOX OF AZORHIZOBIUM-CAULINODANS ORS571 REVEAL A COMMON STRUCTURE IN PROMOTERS REGULATED BY LYSR-TYPE PROTEINS
CONSERVED MOTIFS IN A DIVERGENT NOD BOX OF AZORHIZOBIUM-CAULINODANS ORS571 REVEAL A COMMON STRUCTURE IN PROMOTERS REGULATED BY LYSR-TYPE PROTEINS
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DOI：
10.1073/pnas.89.5.1646
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发表时间：
1992-03-01
影响因子：
11.1
通讯作者：
HOLSTERS, M
中科院分区：
文献类型：
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作者：
GOETHALS, K;VANMONTAGU, M;HOLSTERS, M
根瘤菌、慢生根瘤菌和固氮根瘤菌对豆科植物的结瘤。取决于植物宿主对不同细菌结瘤（nod）基因座的诱导。当 NodD 蛋白（一种 LysR 型激活剂）与 nod 启动子中存在的特定序列结合时，这些 nod 基因座的转录在植物产生的类黄酮存在下被激活。最初，一个称为 nod box 的 47 个碱基对 (bp) 区域被证明是 NodD 结合的靶序列。通过比较 (brady) 根瘤菌的 nod box 序列与来自 Azorhizobium caulinodans 的更不同的 nod box 序列，我们现在提出了一种 nodbox 的模块化构建，其中序列 A-T-C-N9-G-A-T 作为 NodD 蛋白 (NodD box) 的结合靶标。更一般地，我们表明LysR型调节启动子含有特征序列T-N11-A作为反向重复的核心，并提出这是参与与LysR型蛋白质特异性结合的“LysR基序”。在 NodD 盒中对该基序进行位点特异性诱变获得的数据支持了这一提议。此外，我们提供了强有力的论据，即诱导剂类黄酮参与固氮根瘤菌 nod 基因的转录激活，直接与 NodD 蛋白相互作用，从而增加其与 NodD 盒的结合亲和力。
Nodulation of leguminous plants by Rhizobium, Bradyrhizobium, and Azorhizobium spp. is dependent on the induction by the plant host of different bacterial nodulation (nod) loci. The transcription of these nod loci is activated in the presence of plant-produced flavonoids upon binding of the NodD protein-a LysR-type activator-to specific sequences present in the nod promoters. Originally, a 47-base-pair (bp) region called the nod box was shown to be the target sequence for binding of NodD. From the comparison of the nod box sequences of (brady)rhizobia with a more divergent nod box from Azorhizobium caulinodans, we now propose a modular build-up of the nod box with the sequence A-T-C-N9-G-A-T as the binding target of the NodD protein (the NodD box). More generally, we show that LysR-type-regulated promoters contain the characteristic sequence T-N11-A as the core of an inverted repeat and propose this to be the "LysR motif" involved in specific binding to LysR-type proteins. Data obtained upon site-specific mutagenesis of this motif in the NodD box sustains this proposal. Further, we provide strong arguments that the inducer flavonoid, involved in transcriptional activation of Azorhizobium nod genes, interacts directly with the NodD protein, thereby increasing its binding affinities for the NodD box.