A mutation in the cytosolic O-acetylserine (thiol) lyase induces a genome-dependent early leaf death phenotype in <it>Arabidopsis</it>

• Main Authors: Schippers Jos HM, Everts Gerja E, Jing Hai-Chun, Shirzadian-Khorramabad Reza, Hille Jacques, Dijkwel Paul P
• Format: Article
• Language: English
• Published: BMC 2010-04-01
• Series: BMC Plant Biology
• Online Access: http://www.biomedcentral.com/1471-2229/10/80

<p>Abstract</p> <p>Background</p> <p>Cysteine is a component in organic compounds including glutathione that have been implicated in the adaptation of plants to stresses. <it>O</it>-acetylserine (thiol) lyase (OAS-TL) catalyses the final step of cysteine biosynthesis. OAS-TL enzyme isoforms are localised in the cytoplasm, the plastids and mitochondria but the contribution of individual OAS-TL isoforms to plant sulphur metabolism has not yet been fully clarified.</p> <p>Results</p> <p>The seedling lethal phenotype of the <it>Arabidopsis onset of leaf death3-1 </it>(<it>old3-1</it>) mutant is due to a point mutation in the <it>OAS-A1 </it>gene, encoding the cytosolic OAS-TL. The mutation causes a single amino acid substitution from Gly¹⁶²to Glu¹⁶², abolishing old3-1 OAS-TL activity <it>in vitro</it>. The <it>old3-1 </it>mutation segregates as a monogenic semi-dominant trait when backcrossed to its wild type accession Landsberg <it>erecta </it>(L<it>er</it>-0) and the Di-2 accession. Consistent with its semi-dominant behaviour, wild type L<it>er</it>-0 plants transformed with the mutated <it>old3-1 </it>gene, displayed the early leaf death phenotype. However, the <it>old3-1 </it>mutation segregates in an 11:4:1 (wild type: semi-dominant: mutant) ratio when backcrossed to the Colombia-0 and Wassilewskija accessions. Thus, the early leaf death phenotype depends on two semi-dominant loci. The second locus that determines the <it>old3-1 </it>early leaf death phenotype is referred to as <it>odd-ler </it>(for <it>old3 </it>determinant in the L<it>er </it>accession) and is located on chromosome 3. The early leaf death phenotype is temperature dependent and is associated with increased expression of defence-response and oxidative-stress marker genes. Independent of the presence of the <it>odd-ler </it>gene, <it>OAS-A1 </it>is involved in maintaining sulphur and thiol levels and is required for resistance against cadmium stress.</p> <p>Conclusions</p> <p>The cytosolic OAS-TL is involved in maintaining organic sulphur levels. The <it>old3-1 </it>mutation causes genome-dependent and independent phenotypes and uncovers a novel function for the mutated OAS-TL in cell death regulation.</p>