Thirty-five MADS box gene homologues were identified through a large-scale cDNA analysis in rice. Based on the nucleotide sequences of the 3'-untranslated region, these clones were classified into 11 independent species. Seven species were found to be new among the rice MADS box gene family, and the other 4 corresponded to the previously reported OsMADS1, OsMADS2, OsMADS4, and OsMADS5. The full nucleotide sequences of the 7 new species were determined. Each clone encoded a deduced protein of 164-267 amino acids. The K-domain of the MADS protein was conserved in all clones though with lower degree in clone S10304. Reverse transcription PCR analysis showed that clones E31254 and E31864 were expressed mainly in panicles. Dendrogram analysis suggested that E31254 and E31864 are close to Arabidopsis AGL9 and AP1, respectively. Restriction fragment length polymorphism (RFLP) linkage mapping revealed that the rice MADS box gene homologues reported here are not clustered but are located throughout the genome. The locus of E31864 on the RFLP map was closely linked to the long sterile lemma gene, g-1.

To understand the molecular mechanism of G2-arrest of cell division in embryonic diapause of the silkworm, Bombyx mori, we have cloned a cDNA encoding a Bombyx homolog of B-type cyclin. Levels of Bm cyclin-B mRNA were examined during diapause stage and early embryogenesis. The results showed that this G2-arrest did not always correspond to lowered transcriptional levels of cyclin-B, and that the mRNA accumulated in oocytes began to be degraded during the first hour after oviposition, i.e. the first meiosis, suggesting that the penetration of sperm triggered the degradation of maternal cyclin-B mRNA.

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