Inhibition of chalcone synthase expression in anthers of Raphanus sativus with Ogura male sterile cytoplasm.
OBJECTIVE
Expression of the mitochondrial gene orf138 causes Ogura cytoplasmic male sterility (CMS) in Raphanus sativus, but little is known about the mechanism by which CMS takes place. A preliminary microarray experiment revealed that several nuclear genes concerned with flavonoid biosynthesis were inhibited in the male-sterile phenotype. In particular, a gene for one of the key enzymes for flavonoid biosynthesis, chalcone synthase (CHS), was strongly inhibited. A few reports have suggested that the inhibition of CHS causes nuclear-dependent male sterile expression; however, there do not appear to be any reports elucidating the effect of CHS on CMS expression. In this study, the expression patterns of the early genes in the flavonoid biosynthesis pathway, including CHS, were investigated in normal and male-sterile lines.


METHODS
In order to determine the aberrant stage for CMS expression, the characteristics of male-sterile anthers are observed using light and transmission electron microscopy for several stages of flower buds. The expression of CHS and the other flavonoid biosynthetic genes in the anthers were compared between normal and male-sterile types using real time RT-PCR.


RESULTS
Among the flavonoid biosynthetic genes analysed, the expression of CHS was strongly inhibited in the later stages of anther development in sterility cytoplasm; accumulation of putative naringenin derivatives was also inhibited.


CONCLUSIONS
These results show that flavonoids play an important role in the development of functional pollen, not only in nuclear-dependent male sterility, but also in CMS.
Yang
Soojung
S
Department of Biotechnology, Kyoto-Sangyo University, Kyoto 603-8555, Japan.
Terachi
Toru
T
Yamagishi
Hiroshi
H
D000217:Acyltransferases / Q000235:genetics*; D003593:Cytoplasm / Q000235:genetics; D035264:Flowers / Q000235:genetics* / Q000254:growth & development; D015870:Gene Expression; D017343:Genes, Plant; D046529:Microscopy, Electron, Transmission; D024101:Mitochondrial Proteins / Q000235:genetics*; D020411:Oligonucleotide Array Sequence Analysis; D051479:Plant Infertility / Q000235:genetics*; D010940:Plant Proteins / Q000235:genetics*; D011058:Pollen / Q000235:genetics; D031224:Raphanus / Q000235:genetics* / Q000254:growth & development; D020133:Reverse Transcriptase Polymerase Chain Reaction
D024101:Mitochondrial Proteins; D010940:Plant Proteins; C091029:ORF138 protein, Raphanus sativus; D000217:Acyltransferases; C020141:flavanone synthetase