CLONING OF CDNA ENCODING β-CAROTENE HYDROXYLASE FROM CITRUS (CITRUS UNSHIU MARC.)

**CLONING OF CDNA ENCODING β-CAROTENE HYDROXYLASE FROM CITRUS (CITRUS UNSHIU MARC.)**

Authors:	A. Komatsu, Y. Ikoma, M. Omura, M. Yano
Keywords:	β-carotene hydroxylase, gene isolation, 3'-RACE RT-PCR, citrus
Abstract: -Cryptoxanthin, a monohydroxy carotene, is formed from -carotene by hydroxylation at position 3 in one side ring of this symmetrical precursor, whereas zeaxanthin is formed by hydroxylation of both rings. Zeaxanthin is widely distributed in most plants and bacteria. In contrast, the distribution of -cryptoxanthin is limited to several organisms. The juice sacs of Satsuma mandarin (Citrus unshiu Marc.) are one of the tissues in which -cryptoxanthin mainly accumulates. To understand the molecular mechanism of -cryptoxanthin biosynthesis in citrus, we isolated a partial cDNA encoding -carotene hydroxylase by 3'-RACE (rapid amplification of cDNA ends) reverse transcriptase-polymerase chain reaction (RT-PCR) using first-strand cDNA from juice sacs. Full-length cDNA (CitBECH1) encoding -cryptoxanthin was then isolated from the fruit (juice sacs/segments epidermis) cDNA library of Satsuma mandarin using a partial cDNA clone of CitBECH1. The amino acid sequences deduced from the 1158-bp CitBECH1 clone showed marked similarity to -carotene hydroxylase from Arabidopsis (76.3% identity).
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