Enhanced levels of methionine and cysteine in transgenic alfalfa (<i>Medicago sativa</i>L.) plants over‐expressing the<i>Arabidopsis</i>cystathionine γ‐synthase gene

Avraham, Tal; Badani, Hana; Galili, Shmuel; Amir, Rachel

doi:10.1111/j.1467-7652.2004.00102.x

Cited by 76 publications

(38 citation statements)

References 34 publications

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“…These transgenic tobacco plants also exhibited increased tolerance to cadmium presumably due to induction of antioxidant enzymes (Ning et al 2010). Recently, Avraham et al (2005) reported enhanced levels of methionine and cysteine in transgenic alfalfa, a forage crop, by overexpressing Arabidopsis cystathionine c-synthase gene. Importantly, they observed 2.6-and 2.3-fold increases in the levels of free and proteinbound cysteine content, respectively, in these transgenic alfalfa plants.…”

Section: Discussionmentioning

confidence: 97%

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

Kim

Chronis

Juergens

et al. 2011

Planta

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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.

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Section: Discussionmentioning

confidence: 97%

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

Kim

Chronis

Juergens

et al. 2011

Planta

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“…Bellucci et al (2002) and Bagga et al (2004) used endosperm storage protein (zein) of maize, usually rumen-protected and rich in the essential sulfur containing amino acids, to stably express it in alfalfa produced. The transgenic alfalfa plants expressing Arabidopsis cystathionine γ-synthase (AtCGS) showed up to 32-fold, 19-fold, and 2.2-fold increase in the total methionine, S-methylmethionine (SMM), and methionine content of the water-soluble proteins, respectively (Avraham et al 2004). Thus transgenic alfalfa plants with significantly higher levels of methionine and cysteine present promising strategy to improve protein quality.…”

Section: Protein Quality and Utilizationmentioning

confidence: 99%

Biotechnological advancements in alfalfa improvement

Kumar

2011

J Appl Genetics

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Review of biotechnology research in alfalfa shows that molecular techniques are extensively being used for basic and applied research toward alfalfa improvement. Biotechnological approaches have been used in two major areas, genomics and transgenics. In genomics, molecular markers, structural and functional genomics allowed identification of genes of interest and their regulatory components. Alfalfa being obstinate to genetic and genomic analysis, comparative genomics is used for molecular and genetic dissection of various plant processes in alfalfa. Alternatively, transgenic approach involves incorporation of specific and useful genes into alfalfa to improve the traits of interest. Input traits to improve agronomic performance and output traits to improve forage quality, or to produce novel industrial/pharmaceutical proteins, are the focus of current transgenic research in alfalfa. However, transgenic approach is controversial requiring cautious experimental design to combat bioisafety concerns. Ideally, forage alfalfa needs to possess more fermentable carbohydrates, proteins with balanced amino acid profile that degrade slower in rumen, improved winter hardiness, better water use efficiency, pest resistance and no anti-quality factors. Concerted efforts are required to bring together maximum of these characteristic features into the alfalfa plant.

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“…However, a reduction in TS activity in potato caused a far stronger molar increase in methionine levels than the molar decrease in threonine level (Zeh et al, 2001). In addition, in the mto1 Arabidopsis mutant as well as in transgenic tobacco, alfalfa and Arabidopsis plants in which the CGS was overexpressed, significant increases in methionine levels were not accompanied by significant changes in threonine levels (Inba et al, 1994;Gakiere et al, 2000a;Hacham et al, 2002;Kim et al, 2002;Avraham et al, 2005). Moreover, Arabidopsis plants expressing the antisense form of CGS showed a significant increase in OPH level ($21-fold), while threonine was increased only $4-fold (Gakiere et al, 2000b).…”

Section: Introductionmentioning

confidence: 94%

The expression level of threonine synthase and cystathionine-γ-synthase is influenced by the level of both threonine and methionine in Arabidopsis plants

Avraham

Amir

2005

Transgenic Res

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The biosynthesis pathways of the essential amino acids methionine and threonine diverge from O-phosphohomoserine, an intermediate metabolite in the aspartate family of amino acids. Thus, the enzymes cystathionine-gamma-synthase (CGS) in the methionine pathway and threonine synthase (TS), the last enzyme in the threonine pathway, compete for this common substrate. To study this branching point, we overexpressed TS in sense and antisense orientation in Arabidopsis plants with the aim to study its effect on the level of threonine but more importantly on the methionine content. Positive correlation was found not only between TS expression level and threonine content, but also between TS/threonine and CGS expression level. Plants expressing the sense orientation of TS showed a higher level of threonine, increased expression level of CGS, and a significantly higher level of S-methylmethionine, the transport form of methionine. By contrast, plants expressing the antisense form of TS showed lower levels of threonine and of CGS expression level. In these antisense plants, the methionine level increased up to 47-fold compared to wild-type plants. To study further the effect of threonine on CGS expression level, wild-type plants were irrigated with threonine and control plants were irrigated with methionine or water. While threonine increased the expression level of CGS but reduced that of TS, methionine reduced the expression level of CGS but increased that of TS. This data demonstrate that both methionine and threonine affect the two enzymes at the branching point, thus controlling not only their own level, but also the level of each other. This mechanism probably aids in keeping the levels of these two essential amino acids sufficiently high to support plant growth.

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Enhanced levels of methionine and cysteine in transgenic alfalfa (Medicago sativaL.) plants over‐expressing theArabidopsiscystathionine γ‐synthase gene

Cited by 76 publications

References 34 publications

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

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

Biotechnological advancements in alfalfa improvement

The expression level of threonine synthase and cystathionine-γ-synthase is influenced by the level of both threonine and methionine in Arabidopsis plants

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