Plant Molecular Biology 37: 309–318, 1998. 309 c 1998 Kluwer Academic Publishers. Printed in Belgium. The gene encoding T protein of the glycine decarboxylase complex involved in the mitochondrial step of the photorespiratory pathway in plants exhibits features of light-induced genes Pierre Vauclare, David Macherel, Roland Douce and Jacques Bourguignon Laboratoire de Physiologie Cellulaire V´ eg´ etale, CEA, URA CNRS 576, D´ epartement de Biologie Mol´ eculaire et Structurale PVC, CEA Grenoble, 85X, 38054 Grenoble, France ( author for correspondence) Received 28 July 1997; accepted in revised form 3 January 1998 Key words: glycine decarboxylase, light-regulated element, mitochondria, photorespiration Abstract We have isolated and characterized a genomic clone encodingthe 41 kDa monomer T-protein. This gene called gdcT spans approximately 3 kbp and is composed of four exons interrupted by three introns (321, 691 and 114 bp). The splice sites for donor and acceptor are in agreement with the canonical GT/AG rule. Primer extension strongly suggests the presence of two major transcription start sites. The first transcription start site around 43 bases downstream of a putative TATA box was assigned the 1 position. The second ( 31) is not correlated with a putative TATA box, but revealed a pyrimidine-richregion which is very similar to the initiator element. Sequence analysis of the 5 -upstream region of the gene reveals three consensus regions found in the nuclear genes encoding the chloroplastic proteins of ribulose-1,5-bisphosphate carboxylase (rbcS) and the chlorophyll a/b-binding protein (cab) such as an AT-rich sequence localized at 539 to 530, a box II core sequence GGTTAA ( 123 to 118) and between 364 and 354 a tandem GATA motif. These elements are known to be involved respectively in the regulation of light-responsiveness and cell-type specificity expression of plant genes. Gel shift assays indicate that the box II core sequence could bind protein nuclear factors similar to the trans-acting factor which interact with corresponding promoter region of rbcS gene. Introduction The glycine decarboxylase complex (GDC or glycine cleavage system) catalyses the oxidative decarboxylation and deamination of glycine into CO 2 , NH 3 , NADH and N 5 N 10 -methylene-5,6,7,8- tetrahydropteroyl- polyglutamic acid (CH 2 H 4 PteGlu n ). This enzymatic system appears ubiquitous in all organ- isms from bacteria including Peptococcus glycino- philus [23], Arthrobacter globiformis [24] and Escheri- chia coli [37] to eukaryotic cells [13, 21, 33, 38]. In plants, the major role of the GDC, in association with the serine hydroxymethyltransferase (SHMT), is to catalyse the transformation of two molecules of gly- cine into one molecule of serine, which occurs during The nucleotide sequence data reported will appear in the EMBL, GenBank and DDBJ Nucleotide Sequence Databases under the accession number AJ222771 the mitochondrial step of the photorespiratory path- way [20, 27, 34]. The GDC is composed of four different component enzymes designated P protein (a homodimer containing pyridoxal phosphate, 105 kDa), H protein (a monomeric lipoamide-containing pro- tein, 14 kDa), T protein (a monomer catalysing the H 4 PteGlu n -dependent step of the glycine oxidation reaction) and L protein [a homodimer containing flavin adenine dinucleotide (FAD) and a redox active cystine, 59 kDa) [3, 51]. In plants, P, H, T and L proteins are synthesized from nuclear genes [52] which have been localized to the pea genome [46]. The cDNAs cor- responding to these proteins have been isolated and characterized [2, 4, 22, 32, 47, 48] but a few data cor- responding to the regulation of the expression of the GDC components are available. Several investigations have shown that the proteins of the GDC are present in small amounts in etiolated pea leaves and increase