Overexpression of cystathionine-γ-synthase enhances selenium volatilization in Brassica juncea

• Published in: Planta Vol. 218; no. 1; pp. 71 - 78
• Main Authors: Van Huysen, Tiffany, Abdel-Ghany, Salah, Hale, Kerry L., LeDuc, Danika, Terry, Norman, Pilon-Smits, Elizabeth A. H.
• Format: Journal Article
• Language: English
• Published: Berlin Springer-Verlag 01.11.2003; Springer
• Subjects: Agronomy. Soil science and plant productions; Applied sciences; Arabidopsis - enzymology; Arabidopsis - genetics; Biological and medical sciences; Carbon-Oxygen Lyases - genetics; Decontamination. Miscellaneous; Enzymes; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Enzymologic - genetics; Gene Expression Regulation, Plant - genetics; Genetic engineering applications; Genetics and breeding of economic plants; Mustard Plant - enzymology; Mustard Plant - genetics; Mustards; Phytoremediation; Plant breeding: fundamental aspects and methodology; Plant roots; Plants; Plants, Genetically Modified - enzymology; Plants, Genetically Modified - genetics; Pollution; Seedlings; Selenic Acid; Selenium; Selenium - metabolism; Selenium Compounds - metabolism; Sodium Selenite - metabolism; Soil and sediments pollution; Sulfur; Transgenic plants; Vaporizing; Volatilization; Cysteine; Gene overexpression; Lyases; Selenium Organic compounds; Arabidopsis thaliana; Sulfate assimilation; Decontamination; Cruciferae; Dicotyledones; Volatilization; Angiospermae; Transgenic plant; O-Succinylhomoserine (thiol)-lyase; Selenium; Brassica juncea; Volatile compound; Cystathionine-y-synthase; Enzyme; Tolerance; Phytoremediation; Sulfur containing aminoacid; Transgenics; Brassica; Genetic improvement; Selenates; Spermatophyta; Biological accumulation; Selenites; Carbon-oxygen lyases; Oil plant (vegetal)
• ISSN: 0032-0935; 1432-2048
• DOI: 10.1007/s00425-003-1070-z

Selenium (Se) can be assimilated and volatilized via the sulfate assimilation pathway. Cystathionine-γ-synthase (CGS) is thought to catalyze the synthesis of Se-cystathionine from Se-cysteine, the first step in the conversion of Se-cysteine to volatile dimethylselenide. Here the hypothesis was tested that CGS is a rate-limiting enzyme for Se volatilization. Cystathionine-γ-synthase from Arabidopsis thaliana (L.) Heynh. was overexpressed in Indian mustard [Brassica juncea (L.) Czern & Coss], and five transgenic CGS lines with up to 10-fold enhanced CGS levels were compared with wild-type Indian mustard with respect to Se volatilization, tolerance and accumulation. The CGS transgenics showed 2- to 3-fold higher Se volatilization rates than wild-type plants when supplied with selenate or selenite. Transgenic CGS plants contained 20—40% lower shoot Se levels and 50—70% lower root Se levels than the wild type when supplied with selenite. Furthermore, CGS seedlings were more tolerant to selenite than the wild type. There were no differences in Se accumulation or tolerance from selenate, in agreement with the earlier finding that selenate-to-selenite reduction is rate-limiting for selenate tolerance and accumulation. In conclusion, CGS appears to be a rate-limiting enzyme for Se volatilization. Overexpression of CGS offers a promising approach for the creation of plants with enhanced capacity to remove Se from contaminated sites in the form of low-toxic volatile dimethylselenide.