title: Regulation of carotenoid composition and shoot branching in Arabidopsis by a chromatin modifying histone methyltransferase, SDG8.
abstract: Carotenoid pigments are critical for plant survival, and carotenoid composition is tuned to the developmental stage, tissue, and to environmental stimuli. We report the cloning of the CAROTENOID CHLOROPLAST REGULATORY1 (CCR1) gene. The ccr1 mutant has increased shoot branching and altered carotenoid composition, namely, reduced lutein in leaves and accumulation of cis-carotenes in dark-grown seedlings. The CCR1 gene was previously isolated as EARLY FLOWERING IN SHORT DAYS and encodes a histone methyltransferase (SET DOMAIN GROUP 8) that methylates histone H3 on Lys 4 and/or 36 (H3K4 and H3K36). ccr1 plants show reduced trimethyl-H3K4 and increased dimethyl-H3K4 surrounding the CAROTENOID ISOMERASE (CRTISO) translation start site, which correlates with low levels of CRTISO mRNA. Microarrays of ccr1 revealed the downregulation of 85 genes, including CRTISO and genes associated with signaling and development, and upregulation of just 28 genes. The reduction in CRTISO transcript abundance explains the altered carotenoid profile. The changes in shoot branching are additive with more axillary branching mutants, but the altered carotenoid profile may partially affect shoot branching, potentially by perturbed biosynthesis of the carotenoid substrates of strigolactones. These results are consistent with SDG8 regulating shoot meristem activity and carotenoid biosynthesis by modifying the chromatin surrounding key genes, including CRTISO. Thus, the level of lutein, the most abundant carotenoid in higher plants that is critical for photosynthesis and photoprotection, appears to be regulated by a chromatin modifying enzyme in Arabidopsis thaliana.
authors.affiliation: Australian Research Council Centre of Excellence in Plant Energy Biology, School of Biochemistry and Molecular Biology, Australian National University, Canberra, ACT 0200, Australia.
authors.forename: Christopher I
authors.initials: CI
authors.lastname: Cazzonelli
authors.forename: Abby J
authors.initials: AJ
authors.lastname: Cuttriss
authors.forename: Susan B
authors.initials: SB
authors.lastname: Cossetto
authors.forename: William
authors.initials: W
authors.lastname: Pye
authors.forename: Peter
authors.initials: P
authors.lastname: Crisp
authors.forename: Jim
authors.initials: J
authors.lastname: Whelan
authors.forename: E Jean
authors.initials: EJ
authors.lastname: Finnegan
authors.forename: Colin
authors.initials: C
authors.lastname: Turnbull
authors.forename: Barry J
authors.initials: BJ
authors.lastname: Pogson
mesh_terms: D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002338:Carotenoids / Q000096:biosynthesis*; D002734:Chlorophyll / Q000032:analysis; D003001:Cloning, Molecular; D018744:DNA, Plant / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D000076983:Histone Methyltransferases; D011495:Histone-Lysine N-Methyltransferase; D006657:Histones / Q000378:metabolism; D007210:Indoleacetic Acids / Q000032:analysis; D014975:Lutein / Q000096:biosynthesis; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D018520:Plant Shoots / Q000254:growth & development; D011496:Protein Methyltransferases / Q000235:genetics / Q000378:metabolism*; D019745:cis-trans-Isomerases / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D018744:DNA, Plant; D006657:Histones; D007210:Indoleacetic Acids; D002734:Chlorophyll; D002338:Carotenoids; D000076983:Histone Methyltransferases; D011496:Protein Methyltransferases; D011495:Histone-Lysine N-Methyltransferase; C444651:CRTISO protein, Arabidopsis; D019745:cis-trans-Isomerases; D014975:Lutein