[Molecular cloning and characterization of BcMYBogu, a novel member of the MYB family involved in OguCMS in Brassica campestris ssp. chinensis].

In the attempt to elucidate the molecular mechanism of CMS. Ogura cytoplasmic male sterile (OguCMS) lines were obtained in Chinese cabbage after interspecific hybridization between Brassica. napus L. OguCMS and B. campestris ssp. chinensis followed by recurrent backcross with B. campestris ssp. chinensis as the pollen donor. The CMS lines were significantly characterized by the whitish anther and indehiscence of anther. The tapetal hypertrophy with excess vacuola-tion was the first observed defective soon after the tetrad stage, subsequently the microspores defected in pollen wall forma-tion, and later the cytoplasm detached from the exine wall and underwent degeneration. With aid of cDNA-AFLP and RACE approaches, we cloned the BcMYBogu(GenBank accession No: EF127861) in Chinese cabbage, which is premature expressed in early and middle stage floral buds of OguCMS lines, and predicted to encode a novel protein with a DNA binding domain: SH[AL]QKY[RF] motif at the N-terminus. Phylogenetic comparison revealed that the BcMYBogu was clustered with AtMYB32, AtMYB26 and AtMYB4, which were indicated to be involved in male sterility in Arabidopsis thaliana. The BcMYBogu transcript was detected in rosette leaves, floral buds and stems by RT-PCR analysis. Compared with the maintainer, the expression level of BcMYBogu was increased in these organs, especially in floral buds of OguCMS lines. Our investigation suggests that BcMYBogu is a new member of the MYB family involved in male sterility in Chinese cabbage.

[Cloning and Evolutionary Analysis of Homologous Sequences of CYP86MF Gene in Cruciferae.].

In order to direct the construction of plant germplasms by elucidating the relatives among plants at the level of gene, CYP86MF gene analogues from 11 species of 6 genera in Cuciferae were respectively obtained by PCR strategy using gene specific primers designed from conserved regions of CYP86MF gene reported. Sequence comparisonindicated that the similarities among the genes at nucleotide level were over 80%, and the similarities at amino acid level remained above 70%. The differences between the genes at nucleotide and amino acid level between species were 1.0% ~ 5.7% and 2.6% ~ 7.3% respectively, while those between genera 5.6% ~ 22.5% and 7.3% ~ 31.2%, respectively. Phylogenetic analysis showed that Brassica was closely related to Raphanus, followed by Rorippa Scop, Arabidopsis Heynh, Capsella Medic orderly, most distantly related to Orychophrogmus. It was concluded that CYP86MF gene was not applicable to specie and subspecie taxon but genus taxon because the differences of sequences in nucleotides and amino acids were lower between species than genera.

[Establishment of an efficient regeneration system for Chinese cabbage cultured in vitro and histological observation of shoot development].

An efficient plant regeneration system from explants of petiole with cotyledon was developed for Chinese cabbage (Brassica campestris ssp. chinensis Makino) in our study. High frequency of shoot regeneration was obtained in the medium containing BAP 2 mg/L, NAA 0.45 mg/L and 5-7.5 mg/L AgNO3 solution to the half of NH4+ concentration's MS basic medium, with 84.3 percent being the highest frequency of shoot regeneration in seven Chinese cabbage cultivars and one parentage, and the new formed shoots were observed six days after inoculation. Factors influencing in vitro explant regeneration were further studied. The results showed that there was positive correlation between frequency of shoot regeneration and number of shoots per explant. The regeneration plants produced flowers and fruits after about 50 days with low temperature treatment from 8 degrees C to 16 degrees C. Moreover, histological observation indicated that the mode of plant regeneration in B. campestris ssp. chinensis was similar to that of other Brassica crops, and adventitions buds were formed from globular meristematic cluster which derived from the cells of vascular parenchyma at the cut surface of petiole.