An evaluation of the basis and consequences of a stay-green mutation in the navel negra citrus mutant using transcriptomic and proteomic profiling and metabolite analysis.
A Citrus sinensis spontaneous mutant, navel negra (nan), produces fruit with an abnormal brown-colored flavedo during ripening. Analysis of pigment composition in the wild-type and nan flavedo suggested that typical ripening-related chlorophyll (Chl) degradation, but not carotenoid biosynthesis, was impaired in the mutant, identifying nan as a type C stay-green mutant. nan exhibited normal expression of Chl biosynthetic and catabolic genes and chlorophyllase activity but no accumulation of dephytylated Chl compounds during ripening, suggesting that the mutation is not related to a lesion in any of the principal enzymatic steps in Chl catabolism. Transcript profiling using a citrus microarray indicated that a citrus ortholog of a number of SGR (for STAY-GREEN) genes was expressed at substantially lower levels in nan, both prior to and during ripening. However, the pattern of catabolite accumulation and SGR sequence analysis suggested that the nan mutation is distinct from those in previously described stay-green mutants and is associated with an upstream regulatory step, rather than directly influencing a specific component of Chl catabolism. Transcriptomic and comparative proteomic profiling further indicated that the nan mutation resulted in the suppressed expression of numerous photosynthesis-related genes and in the induction of genes that are associated with oxidative stress. These data, along with metabolite analyses, suggest that nan fruit employ a number of molecular mechanisms to compensate for the elevated Chl levels and associated photooxidative stress.
Alós
Enriqueta
E
Instituto Valenciano de Investigaciones Agrarias, Centro de Genómica, 46113 Moncada, Valencia, Spain.
Roca
María
M
Iglesias
Domingo José
DJ
Mínguez-Mosquera
Maria Isabel
MI
Damasceno
Cynthia Maria Borges
CM
Thannhauser
Theodore William
TW
Rose
Jocelyn Kenneth Campbell
JK
Talón
Manuel
M
Cercós
Manuel
M
D029681:Arabidopsis Proteins; D002265:Carboxylic Ester Hydrolases / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism*; D032084:Citrus sinensis / Q000235:genetics* / Q000378:metabolism*; D015180:Electrophoresis, Gel, Two-Dimensional; D005030:Ethylenes / Q000378:metabolism; D005638:Fruit / Q000378:metabolism*; D015870:Gene Expression; D020869:Gene Expression Profiling; D008969:Molecular Sequence Data; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D010940:Plant Proteins / Q000378:metabolism; D020543:Proteome
D029681:Arabidopsis Proteins; C078410:ELIP protein, Arabidopsis; D005030:Ethylenes; D010940:Plant Proteins; D020543:Proteome; D002734:Chlorophyll; C036216:ethylene; D002265:Carboxylic Ester Hydrolases; C019875:chlorophyllase