Iron, heme, and oxygen regulation of the hemA and sdh genes from the soybean symbiont Bradyrhizobium japonicum

Author

Jiyeon Park

Keywords and Phrases

Bradyrhizobium japonicum

Abstract

"During symbiosis, iron, heme, and oxygen play a central role in the metabolism of the bacterial partner, Bradyrhizobium japonicum. We are interested in regulation of gene expression by iron, heme, and oxygen and chose one gene involved in the synthesis of heme and another in which iron and heme are critical components of the gene product. The hemA gene encodes the enzyme ~-aminolevulinic acid synthase which catalyzes the first committed step in heme biosynthesis, condensation of glycine and succinyl-CoA to form ~-aminolevulinic acid. The sdh genes encode the enzyme succinate dehydrogenase, a cytochrome containing component of the respiratory chain. Expression of translational fusions between the hemA and sdh genes and lacZ are both higher in cells grown under iron sut1icient conditions as compared to cells grown under iron deficient conditions. However, in a heme deficient strain, the hemA fusion shows elevated expression. Comparing iron regulated expression of hemA::lacZ transcriptional and translational fusions ruled out possible translational regulation of hemA expression. In contrast, comparing the heme regulation of the hemA ::lacZ transcriptional and tranlational fusions, it appears that heme regulation may be mediated by translational factors. To fmther investigate the mechanisms of iron regulation, we constructed four 10 bp deletions within the 5' UTR by replacing 16 bases with the 6 base recognition sequence for Bg/11 resulting in a net loss of 10 bases. It was observed that deletions ~2, ~3 and ~4 are regulated like wild-type constructs under all conditions. However, expression of the deletion nearest the 5' end of the transcript (~1) is no longer induced under iron sufficient conditions. A model is proposed in which regulation of the B. japonicum hemA gene by iron is post-transcriptional, possibly through modification of mRNA stability. Unlike previous work which showed that the expression of the hemA gene in B. japonicum was increased under oxygen-limited conditions, in our hands, expression of hemA-lacZ translational and transcriptional fusions, is not induced by restricted aeration"--Abstract, page iii.

Advisor(s)

Westenberg, David J.

Committee Member(s)

Mormile, Melaine R.
Ercal, Nuran

Department(s)

Biological Sciences

Degree Name

M.S. in Applied and Environmental Biology

Publisher

University of Missouri--Rolla

Publication Date

Summer 2005

Pagination

viii, 49 pages

Note about bibliography

Includes bibliographical references (pages 42-48)

Rights

© 2005 Jiyeon Park, All rights reserved.

Document Type

Thesis - Restricted Access

File Type

text

Language

English

Subject Headings

Rhizobium japonicum -- GeneticsGenetic regulationSoybean -- Analysis

Thesis Number

T 8810

Print OCLC #

63189509

Recommended Citation

Park, Jiyeon, "Iron, heme, and oxygen regulation of the hemA and sdh genes from the soybean symbiont Bradyrhizobium japonicum" (2005). Masters Theses. 3750.
https://scholarsmine.mst.edu/masters_theses/3750