Catalyzes the acyloin condensation reaction between C atoms 2 and 3 of pyruvate and glyceraldehyde 3-phosphate to yield 1-deoxy-D-xylulose-5-phosphate (DXP). Is a limiting enzyme for plastidic isoprenoid biosynthesis and essential for chloroplast development. D-glyceraldehyde 3-phosphate + H(+) + pyruvate = 1-deoxy-D-xylulose 5-phosphate + CO2 Binds 1 Mg(2+) ion per subunit. Binds 1 thiamine pyrophosphate per subunit. Metabolic intermediate biosynthesis; 1-deoxy-D-xylulose 5-phosphate biosynthesis; 1-deoxy-D-xylulose 5-phosphate from D-glyceraldehyde 3-phosphate and pyruvate: step 1/1. Homodimer. Widely expressed. Circadian-regulated with a peak in the late period of dark phase and early period of the light phase. Albino phenotype and seedling lethal when homozygous. The phenotype is caused by an early arrest in chloroplast differentiation. Plants over-expressing CLA1 show increased levels of plastid isoprenoids derived from the methylerythritol 4-phosphate (MEP) pathway, such as chlorophylls, tocopherols, carotenoids, abscisic acid, and gibberellin (PubMed:11264287). Mutant plants treated with exogenous mevalonic acid partially recover chlorophyll accumulation and plastid development (PubMed:12447549). Belongs to the transketolase family. DXPS subfamily. Extended N-terminus.