The gene expression profile of carotenoid biosynthetic pathway and the functional role of Carotenoid Cleavage Dioxygenase (CCD) in Oncidium floral tissues
Date Issued
2011
Date
2011
Author(s)
Pan, Hsin-An
Abstract
Oncidium Gower Ramsey ‘Sunkist’ (Sun) and Oncidium Gower Ramsey ‘White Jade’ (WJ), occurred naturally from an original variety of Oncidium Gower Ramsey (GR) in an orchid farm. This study was to analyze and examine the relationship of carotenoid biosynthesis and accumulation mechanisms and coloration diversities among these three cultivars, and physiological and biochemical functions of OgCCD1s and OgNCED. The HPLC analysis revealed that yellow Gower Ramsey accumulated lutein, violaxathin, 9-cis-violaxathin and neoxanthin; orange ‘Sunkist’ accumulated an additional β-carotene, and ‘White Jade’ is devoid of carotenoid compounds. ‘White Jade’ contained higher ABA and its flower senescence was accelerated. Nine expressed genes involved in carotenoid biosynthesis in mature bud period were analyzed and found that expression level of β-hydroxylase (OgHYB) and zeaxathin epoxidase (OgZEP) was displayed in yellow Gower Ramsey, relative to the down-regulation of OgHYB and OgZEP exhibited in orange Sunkist, which resulted in the accumulation of β-carotene and orange coloration in ‘Sunkist’ floral tissues. However, White Jade is caused by the up-regulation of OgCCD1 (Carotenoid Cleavage Dioxygenase 1), which catabolizes carotenoid metabolites. Transient expression of bud-specific promoter (Pchrc) driven OgCCD1 in yellow lip tissues of Gower Ramsey by bombardment confirmed its function on disintegrating carotenoid compounds. Methylation assay of OgCCD1 promoter in White Jade and Gower Ramsey revealed that hyper DNA methylation presented in OgCCD1 promoter region of Gower Ramsey, but not in that of White Jade. It suggests that OgCCD1 involved in pigmentation loss of ‘White Jade’.
Five members of OgCCD1 family were cloned form flower tissue of White Jade and Gower Ramsey with Lambda phage cDNA library. Localization of OgCCD1 and OgNCED in protoplast of Arabidopsis by Confocal microscopy revealed that OgCCD1 was expressed in the chloroplast membrane and cytosol and OgNCED was expressed in the chloroplast. In addition, OgCCD1s and OgNCED T3 transgenic Arabidopsis showed shorter root length, higher ABA content, more apocarotenoid accumulation and early senescence, and poor tolerance with abiotic stress than control group.
This study suggested that OgCCD1 is involved in the formation of white floral coloration flower in Oncidium Gower Ramsey ‘White Jade’ by disintegrating carotenoid compounds.
Subjects
Oncidium Gower Ramsey
Oncidium Gower Ramsey ‘Sunkist’
Oncidium Gower Ramsey ‘White Jade’
carotenoid
carotenoid cleavage dioxygenase
Type
thesis
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