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Modulation of NodD1 activity by flav...

Peck, Melicent Clare.

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Modulation of NodD1 activity by flavonoids in Sinorhizobium meliloti.

紀錄類型:	書目-語言資料,印刷品 : Monograph/item
正題名/作者:	Modulation of NodD1 activity by flavonoids in Sinorhizobium meliloti./
作者:	Peck, Melicent Clare.
面頁冊數:	236 p.
附註:	Adviser: Sharon Long.
Contained By:	Dissertation Abstracts International63-10B.
標題:	Biology, Microbiology. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3067914
ISBN:	0493875336

Modulation of NodD1 activity by flavonoids in Sinorhizobium meliloti.
Peck, Melicent Clare.

Modulation of NodD1 activity by flavonoids in Sinorhizobium meliloti. - 236 p.

Adviser: Sharon Long.

Thesis (Ph.D.)--Stanford University, 2002.

To initiate symbiosis, <italic>Sinorhizobium meliloti</italic> responds to a unique spectrum of flavonoid inducers, including luteolin, secreted from the legume alfalfa. Flavonoids are required to initiate transcription of the <italic> nod</italic> genes, which are directly regulated by the NodD family of transcriptional activators. In <italic>S. meliloti</italic> three distinct genes encode NodD-like regulators: <italic>nodD1, nodD2</italic>, and <italic>nodD3</italic>. NodD1 and NodD2 require a co-inducer for their activity; conversely, NodD3 is constitutively active when over-expressed. The three members of the NodD family show about 80% identity.

ISBN: 0493875336Subjects--Topical Terms:

1017734
Biology, Microbiology.

Modulation of NodD1 activity by flavonoids in Sinorhizobium meliloti.
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245 1 0 $a Modulation of NodD1 activity by flavonoids in Sinorhizobium meliloti.
300 $a 236 p.
500 $a Adviser: Sharon Long.
500 $a Source: Dissertation Abstracts International, Volume: 63-10, Section: B, page: 4488.
502 $a Thesis (Ph.D.)--Stanford University, 2002.
520 $a To initiate symbiosis, <italic>Sinorhizobium meliloti</italic> responds to a unique spectrum of flavonoid inducers, including luteolin, secreted from the legume alfalfa. Flavonoids are required to initiate transcription of the <italic> nod</italic> genes, which are directly regulated by the NodD family of transcriptional activators. In <italic>S. meliloti</italic> three distinct genes encode NodD-like regulators: <italic>nodD1, nodD2</italic>, and <italic>nodD3</italic>. NodD1 and NodD2 require a co-inducer for their activity; conversely, NodD3 is constitutively active when over-expressed. The three members of the NodD family show about 80% identity.
520 $a Little is know about how NodD1-dependent transcription is activated by inducers. For example, luteolin may affect NodD1 multimerization, DNA binding, or interaction with RNA polymerase. To address this question, we purified NodD1 and analyzed its DNA binding properties in the absence versus presence of luteolin. When NodD1 is purified from cells grown with luteolin it displays a 2–3 fold higher DNA binding affinity for <italic>nod</italic> gene promoters than the same protein purified from cells grown in the absence of luteolin. Furthermore, a similar increase in NodD-<italic>nod</italic> gene DNA binding affinity is observed when luteolin is added directly to purified NodD1 <italic>in vitro</italic>. Interestingly, flavonoids that do not induce <italic> nod</italic> gene activity in <italic>S. meliloti</italic> also stimulate NodD1 binding to <italic>nod</italic> gene promoters. Using <italic>in vivo </italic> competition assays, we demonstrated that non-inducing flavonoids act as competitive inhibitors of luteolin during NodD1-mediated <italic>nod </italic> gene transcription.
520 $a To characterize the NodD1 domains that are involved in luteolin perception and binding and in the activation of <italic>nod</italic> gene transcription, NodD1 mutants were isolated that demonstrate altered responses to luteolin. The first mutant shows elevated levels of nod gene expression in the absence of luteolin, yet expression decreases in the presence of luteolin. The second mutant shows elevated <italic>nod</italic> gene expression in the absence of luteolin, yet remains inducible. The third mutant shows enhanced levels of <italic>nod</italic> gene expression in the presence of luteolin. Each mutant binds to <italic>nod</italic> gene promoters with lower affinity than wild-type NodD1; however, the DNA binding affinity is stimulated by luteolin. By mapping the mutations onto a model of NodD1, we have begun to identify distinct luteolin binding and activation domains.
590 $a School code: 0212.
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650 4 $a Chemistry, Biochemistry. $3 1017722
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