An Evaluation of the Basis and Consequences of a Stay-Green Mutation in thenavel negraCitrus Mutant Using Transcriptomic and Proteomic Profiling and Metabolite Analysis  

Abstract

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.

Effects of 1-MCP on chlorophyll degradation pathway-associated genes expression and chloroplast ultrastructure during the peel yellowing of Chinese pear fruits in storage

“…Recently, the stay-green (SGR) genes have been cloned from different plant species (Armstead et al, 2006;Barry, McQuinn, Chung, Besuden, & Giovannoni, 2008;Jiang et al, 2007;Park et al, 2007;Sato, Morita, Nishimura, Yamaguchi, & Kusaba, 2007). Further analyses indicate that the expression of SGR is closely associated with leaf senescence and fruit ripening (Alós et al, 2008;Armstead et al, 2006;Barry et al, 2008;Hörten-steiner, 2006;Sato et al, 2007;Yang et al, 2009). Despite the fact that the primary pathway of leaf chlorophyll degradation has been well known, the factors that initiate chlorophyll degradation have still not been understood.…”

Use of a custom array to study differentially expressed genes during blood orange (Citrus sinensis L. Osbeck) ripening

“…The latter is commonly employed to investigate expression profiling in many crops. In recent years, several microarray studies involving the Citrus genome have been reported (Shimada et al, 2005;Cerc os et al, 2006;Fujii et al, 2007;Alos et al, 2008). In 2006, Affymetrix developed and released a citrus GeneChip (http://www.affymetrix.com/analysis/ index.affx).…”

Transcriptome profiling of peanut (Arachis hypogaea) gynophores in gravitropic response

“…Quantitative real-time RT-PCR was performed with SYBR Premix Ex Taq II kit (Takara) in LightCycler 480 instrument (Roche) equipped with Light-Cycler Software ver. 1.5 (Roche) according to the manufacturer's instructions (Alos et al 2008). All the primers specific for selected peanut genes were designed using the Primer ver.…”