Transcriptome analysis in petals and leaves of chrysanthemums with different chlorophyll levels

To identify the regulatory steps that control chlorophyll accumulation, we compared gene expression in petals and leaves of chrysanthemum cultivars with different chlorophyll levels. Microarray analyses showed that the expression levels of chlorophyll biosynthesis genes encoding glutamyl-tRNA reductase, Mg-protoporphyrin IX chelatase, Mg-protoporphyrin IX monomethylester cyclase, and protochlorophyllorophyllide oxidoreductase were well associated with chlorophyll content: their expression levels were lower in white petals than in green petals, and were highest in leaves. Among chlorophyll catabolic genes, expression of STAY-GREEN, encoding Mg-dechelatase, which is a key enzyme controlling chlorophyll degradation, was considerably higher in white and green petals than in leaves. We searched for transcription factor genes whose expression was well related to chlorophyll level in petals and leaves and found several such genes. Expression of white petals (FW, Feeling White), green petals (FG, Feering Green; FGII, Feeling Green Dark), and mature leaves of chrysanthemums was analyzed. The analysis was performed in biological triplicate.