A novel gene mutation that confers abnormal patterns of β‐carotene accumulation in cauliflower (Brassica oleracea var. botrytis)

Abstract

SummaryThe Or gene of cauli¯ower (Brassica oleracea var. botrytis) causes many tissues of the plant to accumulate carotenoids and turn orange, which is suggestive of a perturbation of the normal regulation of carotenogenesis. A series of experiments to explore the cellular basis of the carotenoid accumulation induced by the Or gene was completed. The Or gene causes obvious carotenoid accumulation in weakly or unpigmented tissues such as the curd, pith, leaf bases and shoot meristems, and cryptically in some cells of other organs, including the roots and developing fruits. The dominant carotenoid accumulated is b-carotene, which can reach levels that are several hundred-fold higher than those in comparable wildtype tissues. The b-carotene accumulates in plastids mainly as a component of massive, highly ordered sheets. The Or gene does not affect carotenoid composition of leaves, nor does it alter color and chromoplast appearance in¯ower petals. Interestingly, mRNA from carotenogenic and other isoprenoid biosynthetic genes upstream of the carotenoid pathway was detected both in orange tissues of the mutant, and in comparable unpigmented wild-type tissues. Thus the unpigmented wild-type tissues are likely to be competent to synthesize carotenoids, but this process is suppressed by an unidenti®ed mechanism. Our results suggest that the Or gene may induce carotenoid accumulation by initiating the synthesis of a carotenoid deposition sink in the form of the large carotenoid-sequestering sheets.

Carotenoids in nature: insights from plants and beyond

“…A naturally occurring mutation in the Brassica oleracea orange-curd (or) gene changes a normally white cauliflower curd into an orange Or mutant, which accumulates high levels of b-carotene . The OR gene encodes a DnaJ cysteine-rich domain-containing protein and plays a role in coordinating the differentiation of proplastids in the shoot and inflorescence meristems of the curd into chromoplasts (Li et al 2001;Lu et al 2006). Carotenoids accumulate in lipoprotein structures within the chromoplast (Bartley and Scolnik 1995;Vishnevetsky et al 1999), which might allow for additional carotenoid biosynthesis.…”

The Purple Cauliflower Arises from Activation of a MYB Transcription Factor

“…Prehybridization and hybridization with P 32 -labeled probes were performed as described previously (Li et al, 2001). Probes used included CHS (U21762), CHI (U20894), F3H (U14735), and LDOX (YAY780) from Arabidopsis, as well as F3'H, DFR, UGT, and Actin amplified from white cauliflower DNA using primers as listed in Supplemental Table S1.…”

Development of an integrated approach for evaluation of 2‐D gel image analysis: Impact of multiple proteins in single spots on comparative proteomics in conventional 2‐D gel/MALDI workflow

“…Two grams of frozen curd material of both WT cauliflower and the orange-colored homozygous mutant (Or) [23] were finely powered in liquid nitrogen using a pestle and mortar, and suspended in 10 mL of extraction buffer (1% polyvinylpolypyrrolidone, 0.1 M sucrose, 0.1 M KCl, 0.1 M Tris (pH 7.5), 50 mM EDTA, 1 mM PMSF, and 10 mM DTT). The extraction was homogenized at 47C for 30 min followed by centrifugation at 4000 rpm for 30 min.…”

“…As part of a study to understand the mechanisms involved in the accumulation of carotenoids in a cauliflower mutant [23], we applied 2-DE to separate proteins extracted from the edible curd of both homozygous wild-type (WT) cauliflower and the orange-colored homozygous mutant (Or), to identify proteins associated with the accumulation of carotenoids. Here, we report the comparison of protein identifications made by direct MALDI-TOF/TOF and CapLC-ESI-MS/MS analysis.…”