The cauliflower Or gene encodes a DnaJ cysteine-rich domain-containing protein that mediates high levels of beta-carotene accumulation.
Despite recent progress in our understanding of carotenogenesis in plants, the mechanisms that govern overall carotenoid accumulation remain largely unknown. The Orange (Or) gene mutation in cauliflower (Brassica oleracea var botrytis) confers the accumulation of high levels of beta-carotene in various tissues normally devoid of carotenoids. Using positional cloning, we isolated the gene representing Or and verified it by functional complementation in wild-type cauliflower. Or encodes a plastid-associated protein containing a DnaJ Cys-rich domain. The Or gene mutation is due to the insertion of a long terminal repeat retrotransposon in the Or allele. Or appears to be plant specific and is highly conserved among divergent plant species. Analyses of the gene, the gene product, and the cytological effects of the Or transgene suggest that the functional role of Or is associated with a cellular process that triggers the differentiation of proplastids or other noncolored plastids into chromoplasts for carotenoid accumulation. Moreover, we demonstrate that Or can be used as a novel genetic tool to induce carotenoid accumulation in a major staple food crop. We show here that controlling the formation of chromoplasts is an important mechanism by which carotenoid accumulation is regulated in plants.
Lu
Shan
S
U.S. Department of Agriculure-Agricultural Research Service, Plant, Soil, and Nutrition Laboratory, Cornell University, Ithaca, New York 14853, USA.
Van Eck
Joyce
J
Zhou
Xiangjun
X
Lopez
Alex B
AB
O'Halloran
Diana M
DM
Cosman
Kelly M
KM
Conlin
Brian J
BJ
Paolillo
Dominick J
DJ
Garvin
David F
DF
Vrebalov
Julia
J
Kochian
Leon V
LV
Küpper
Hendrik
H
Earle
Elizabeth D
ED
Cao
Jun
J
Li
Li
L
D000483:Alleles; D017398:Alternative Splicing; D000595:Amino Acid Sequence; D001937:Brassica / Q000235:genetics* / Q000378:metabolism*; D002736:Chloroplasts / Q000378:metabolism; D003001:Cloning, Molecular; D017124:Conserved Sequence; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D005816:Genetic Complementation Test; D050956:HSP40 Heat-Shock Proteins / Q000737:chemistry*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D018515:Plant Leaves / Q000166:cytology; D010940:Plant Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D034622:RNA Interference; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011198:Solanum tuberosum / Q000235:genetics; D019207:beta Carotene / Q000378:metabolism*
D050956:HSP40 Heat-Shock Proteins; D008565:Membrane Proteins; C094062:Pftf protein, Capsicum annuum; D010940:Plant Proteins; D012333:RNA, Messenger; D019207:beta Carotene