Isolation and characterization of two cDNAs encoding for compartment specific isoforms of O‐acetylserine (thiol) lyase from Arabidopsis thaliana

Abstract

cDNAs encoding for two isoforms of O-acetylserine (thiol) lyase (OAS-TL), which catalyzes the synthesis of cysteine, have been isolated from Arabidopsis thaliana. Secondary structure together with expression patterns derived during photomorphogenesis indicate cellular localizations in the cytosol and plastids, thus allowing a direct comparison of compartment-specific forms within one species. The cytosolic OAS-TL complemented an E. coli auxotrophic mutant lacking cysteine synthesis. Both isoforms are represented by small gene families. They are expressed under all conditions investigated and were observed to increase in expression in plants grown with limited sulfate supply.

Subcellular Localization of Spinach Cysteine Synthase Isoforms and Regulation of Their Gene Expression by Nitrogen and Sulfur

“…We found only slight differences (1.2-to 1.5-fold) in the mRNA level of CysA and CysB in sulfate-starved cells during the starvation periods of 0 to 24 h compared with cells grown in the normal Murashige-Skoog medium. Hell et al (1994) have demonstrated a 1.5-to 2.0-fold up-regulation of these two Cys isoforms in sulfate-starved Arabidopsis seedlings. However, it is questionable that Cys genes respond directly to the exogenous sulfate supply, reflecting the demands of Cys production for protein synthesis in these subcellular compartments to maintain cell activities.…”

“…To obtain a comprehensive explanation for the different functional roles of CS isoforms, molecular biologic studies have been initiated. Recently, cDNA clones for the nuclear encoded cytoplasmic, chloroplastic/ plastidic, and putative mitochondrial isoforms have been isolated from various plant species (Romer et al, 1992;Saito et al, 1992Saito et al, , 1993Saito et al, , 1994Hell et al, 1993Hell et al, , 1994Rolland et al, 1993;Youssefian et al, 1993;Noji et al, 1994). We have designated the three genes encoding CS isoforms in spinach as CysA (cytoplasmic) (Saito et al, 1992), CysB (chloroplastic/plastidic) (Saito et al, 1993), and CysC (putative mitochondrial) .…”

Analysis of theArabidopsis O-Acetylserine(thiol)lyase Gene Family Demonstrates Compartment-Specific Differences in the Regulation of Cysteine Synthesis

“…The same was true for the oastlAB mutant. The abundance of the five OAS-TL proteins that bound to SAT correlated well with the relative amounts of mRNAs in leaves and roots at this developmental stage in the literature (Hell et al, 1994;Hesse et al, 1999;Hatzfeld et al, 2000;Yamaguchi et al, 2000) and in a public microarray database (Zimmermann et al, 2004).…”

“…In Arabidopsis thaliana, SAT and OAS-TL proteins are encoded by small gene families and distributed between cytoplasm, mitochondria, and plastids (Hell et al, 1994;Bogdanova et al, 1995;reviewed in Hell et al, 2002;Kawashima et al, 2005). According to the Genevestigator database (Zimmermann et al, 2004), the most strongly transcribed genes, out of nine OASTL-like genes, are OASTLA1 (At4g14880), OASTLB (At2g43750), OASTLC (At3g59760), and CYSC1 (At3g61440).…”

Molecular Basis of Cysteine Biosynthesis in Plants

“…Overexpression of OASS in transgenic plants improves heavy metal tolerance (8), increases cysteine biosynthesis in response to sulfur stress (9), and provides protection against oxidative stress (10,11). In Arabidopsis, three tissue-specific OASS isoforms catalyze the formation of cysteine from sulfide and O-acetylserine (12)(13)(14)(15). Likewise, Spinacia oleracea (spinach) expresses a similar set of isoforms (16 -18).…”