Plant and Cell Physiology Advance Access originally published online on July 2, 2007
Plant and Cell Physiology 2007 48(8):1108-1120; doi:10.1093/pcp/pcm084
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A Rice Dihydrosphingosine C4 Hydroxylase (DSH1) Gene, which is Abundantly Expressed in the Stigmas, Vascular Cells and Apical Meristem, may be Involved in Fertility
1Department of Biological Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba, 278-8510 Japan
2Division of Plant Biotechnology, Tissue Engineering Research Center, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba, 278-8510 Japan
*Corresponding author: E-mail, shimadah{at}rs.noda.tus.ac.jp; Fax, +81-4-7125-1841.
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Abstract |
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Dihydrosphingosine C4 hydroxylase is a key enzyme in the biosynthesis of phytosphingosine, a major constituent of sphingolipids in plants and yeasts. The rice genome contains five homologue genes for dihydrosphingosine C4 hydroxylase, DSH1–DSH5, whose gene products show high degrees of homology to the yeast counterpart, SUR2. Among them, expression of DSH1, DSH2 and DSH4 was detected, and DSH1 and DSH4 complement the yeast sur2 mutation. The DSH1 gene was specifically and abundantly expressed in vascular bundles and apical meristems. In particular, very strong expression was detected in the stigmas of flowers. Repression of DSH1 expression by the antisense gene or RNA interference (RNAi) resulted in a severe reduction of fertility. In the transformants in which DSH1 expression was suppressed, significantly increased expression of DSH2 was found in leaves but not in pistils, suggesting that there was tissue-specific correlation between DSH1 and DSH2 expression. Our results indicate that the product of DSH1 may be involved in plant viability or reproductive processes, and that the phenotype of sterility is apparently caused by loss of function of DSH1 in the stigma. It is also suggested that there is a complex mechanism controlling the tissue-specific expression of the DSH1 gene.
Keywords: DSH1 overexpressing and repressed transformants - Fertilization - Homolog of yeast SUR2 - Phytosphingosine - Rice (Oryza sativa) - Tissue-specific expression
Abbreviations: CaMV, cauliflower mosaic virus; DSH, dihydrosphingosine C4 hydroxylase; DHS, dihydrosphingosine; EST, expressed sequence tag; GUS, ß-glucuronidase; LCBs, long chain bases; ORF, open reading frame; PHS, 4-hydroxysphinganine (phytosphingosine); RNAi, RNA interference; RT–PCR, reverse transcriptase–PCR
3Present address: Laboratory of Molecular Biology, Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto, 611-0011 Japan.
(Received April 26, 2007; Accepted June 18, 2007)
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