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Transgenic soybean plants overexpressing O-acetylserine sulfhydrylase accumulate enhanced levels of cysteine and Bowman–Birk protease inhibitor in seeds

Permanent URL:
http://handle.nal.usda.gov/10113/54520
Abstract:
Soybeans provide an excellent source of protein in animal feed. Soybean protein quality can be enhanced by increasing the concentration of sulfur-containing amino acids. Previous attempts to increase the concentration of sulfur-containing amino acids through the expression of heterologous proteins have met with limited success. Here, we report a successful strategy to increase the cysteine content of soybean seed through the overexpression of a key sulfur assimilatory enzyme. We have generated several transgenic soybean plants that overexpress a cytosolic isoform of O-acetylserine sulfhydrylase (OASS). These transgenic soybean plants exhibit a four- to tenfold increase in OASS activity when compared with non-transformed wild-type. The OASS activity in the transgenic soybeans was significantly higher at all the stages of seed development. Unlike the non-transformed soybean plants, there was no marked decrease in the OASS activity even at later stages of seed development. Overexpression of cytosolic OASS resulted in a 58–74% increase in protein-bound cysteine levels compared with non-transformed wild-type soybean seeds. A 22–32% increase in the free cysteine levels was also observed in transgenic soybeans overexpressing OASS. Furthermore, these transgenic soybean plants showed a marked increase in the accumulation of Bowman–Birk protease inhibitor, a cysteine-rich protein. The overall increase in soybean total cysteine content (both free and protein-bound) satisfies the recommended levels required for the optimal growth of monogastric animals.
Author(s):
Won-Seok Kim , Demosthenis Chronis , Matthew Juergens , Amy C. Schroeder , Seung Won Hyun , Joseph M. Jez , Hari B. Krishnan
Subject(s):
Bowman-Birk inhibitor , amino acid composition , animal growth , animal source protein , cysteine , cysteine proteinase inhibitors , developmental stages , enzyme activity , enzymes , feeds , gene overexpression , protein synthesis , proteins , seed development , seeds , soy protein , soybeans , sulfur , transgenic plants
Source:
Planta 2012 1 v.235 no.1
Language:
English
Publisher:
Springer-Verlag
Year:
2012
Collection:
Journal Articles, USDA Authors, Peer-Reviewed
File:
Download [PDF File]
Rights:
Works produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted.