Characterization and Expression Analysis of a Serine Acetyltransferase Gene Family Involved in a Key Step of the Sulfur Assimilation Pathway in Arabidopsis

C.G. Kawashima, Oliver Berkowitz, R. Hell, M. Noji, K. Saito

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104 Citations (Scopus)

Abstract

Ser acetyltransferase (SATase; EC 2.3.1.30) catalyzes the formation of O-acetyl-Ser from L-Ser and acetyl-CoA, leading tosynthesis of Cys. According to its position at the decisive junction of the pathways of sulfur assimilation and amino acidmetabolism, SATases are subject to regulatory mechanisms to control the flux of Cys synthesis. In Arabidopsis (Arabidopsisthaliana) there are five genes encoding SATase-like proteins. Two isoforms, Serat3;1 and Serat3;2, were characterized withrespect to their enzymatic properties, feedback inhibition by L-Cys, and subcellular localization. Functional identity of Serat3;1and Serat3;2 was established by complementation of a SATase-deficient mutant of Escherichia coli. Cytosolic localization ofSerat3;1 and Serat3;2 was confirmed by using fusion construct with the green fluorescent protein. Recombinant Serat3;1 wasnot inhibited by L-Cys, while Serat3;2 was a strongly feedback-inhibited isoform. Quantification of expression patternsindicated that Serat2;1 is the dominant form expressed in most tissues examined, followed by Serat1;1 and Serat2;2. AlthoughSerat3;1 and Serat3;2 were expressed weakly in most tissues, Serat3;2 expression was significantly induced under sulfurdeficiency and cadmium stress as well as during generative developmental stages, implying that Serat3;1 and Serat3;2 havespecific roles when plants are subjected to distinct conditions. Transgenic Arabidopsis plants expressing the green fluorescentprotein under the control of the five promoters indicated that, in all Serat genes, the expression was predominantly localized inthe vascular system, notably in the phloem. These results demonstrate that Arabidopsis employs a complex array ofcompartment-specific SATase isoforms with distinct enzymatic properties and expression patterns to ensure the provision ofCys in response to developmental and environmental changes.
Original languageEnglish
Pages (from-to)220-230
JournalPlant Physiology
Volume137
Issue number1
DOIs
Publication statusPublished - 2005

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