Int. J. Mol. Sci. 2017, 18(12), 2547; https://doi.org/10.3390/ijms18122547
Nodule-Enriched GRETCHEN HAGEN 3 Enzymes Have Distinct Substrate Specificities and Are Important for Proper Soybean Nodule Development
Suresh Damodaran 1, Corey S. Westfall 2, Brian A. Kisely 1, Joseph M. Jez 2,*
and Senthil Subramanian 1,3,*
1
Department of Agronomy, Horticulture and Plant Science, South Dakota State University, Brookings, SD 57007, USA
2
Department of Biology, Washington University in St. Louis, St. Louis, MO 63130, USA
3
Department of Biology and Microbiology, South Dakota State University, Brookings, SD 57007, USA
*
Authors to whom correspondence should be addressed.
Received: 20 October 2017 / Revised: 21 November 2017 / Accepted: 23 November 2017 / Published: 28 November 2017
(This article belongs to the Special Issue Auxin)
Abstract
Legume root nodules develop as a result of a symbiotic relationship between the plant and nitrogen-fixing rhizobia bacteria in soil. Auxin activity is detected in different cell types at different stages of nodule development; as well as an enhanced sensitivity to auxin inhibits, which could affect nodule development. While some transport and signaling mechanisms that achieve precise spatiotemporal auxin output are known, the role of auxin metabolism during nodule development is unclear. Using a soybean root lateral organ transcriptome data set, we identified distinct nodule enrichment of three genes encoding auxin-deactivating GRETCHEN HAGEN 3 (GH3) indole-3-acetic acid (IAA) amido transferase enzymes: GmGH3-11/12, GmGH3-14 and GmGH3-15. In vitro enzymatic assays showed that each of these GH3 proteins preferred IAA and aspartate as acyl and amino acid substrates, respectively. GmGH3-15 showed a broad substrate preference, especially with different forms of auxin. Promoter:GUS expression analysis indicated that GmGH3-14 acts primarily in the root epidermis and the nodule primordium where as GmGH3-15 might act in the vasculature. Silencing the expression of these GH3 genes in soybean composite plants led to altered nodule numbers, maturity, and size. Our results indicate that these GH3s are needed for proper nodule maturation in soybean, but the precise mechanism by which they regulate nodule development remains to be explained. View Full-TextKeywords:
Gretchen Hagen 3 (GH3); auxin; indole-3-acetic acid (IAA); soybean (Glycine max); nodule; artificial microRNA
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Damodaran, S.; Westfall, C.S.; Kisely, B.A.; Jez, J.M.; Subramanian, S. Nodule-Enriched GRETCHEN HAGEN 3 Enzymes Have Distinct Substrate Specificities and Are Important for Proper Soybean Nodule Development. Int. J. Mol. Sci. 2017, 18, 2547.
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