The isolation and expression analysis of four partial gene sequences from rose (Rosa hybrida cv. Linda) belonging to the receptor-like kinase gene superfamily are reported. These genes have been designated RhSERK1 to RhSERK4 (Accession No. EF631967 to EF631970) as they exhibit high sequence identities with genes from the somatic embryogenesis receptor-like kinase (SERK) family in other plant species. The RhSERK genes are differentially expressed in non-embryogenic callus, embryogenic callus, mature somatic embryos and a range of tissues from intact plants, indicating a broad role in plant growth and development. However, the expressions of RhSERK3 and RhSERK4 were approximately fivefold higher in embryogenic callus than in non-embryogenic callus, and they are even higher when compared to tissues from intact plants. In addition, RhSERK4 expression was approximately eightfold higher in somatic embryos than in embryogenic callus. These results suggest that the expression pattern of RhSERK3 and RhSERK4 may be used as a marker of somatic embryogenesis.

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KEY MESSAGE : The P ( SAG12 ) -ipt gene was transferred to miniature rose, as the first woody species, resulting in increased ethylene resistance due to specific up-regulation of the ipt gene under senescence promoting conditions. Transgenic plants of Rosa hybrida 'Linda' were obtained via transformation with Agrobacterium tumefaciens strain harboring the binary vector pSG529(+) containing the P( SAG12 )-ipt construct. A. tumefaciens strains AGL1, GV3850 and LBA4404 (containing P(35S)-INTGUS gene) were used for transformation of embryogenic callus, but transgenic shoots were obtained only when AGL1 was applied. The highest transformation frequency was 10 % and it was achieved when half MS medium was used for the dilution of overnight culture of Agrobacterium. Southern blot confirmed integration of 1-6 copies of the nptII gene into the rose genome in the tested lines. Four transgenic lines were obtained which were morphologically true-to-type and indistinguishable from Wt shoots while they were in in vitro cultures. Adventitious root induction was more difficult in transgenic shoots compared to the Wt shoots, however, one of the transgenic lines (line 6) was rooted and subsequently analyzed phenotypically. The ipt expression levels were determined in this line after exposure to exogenous ethylene (3.5 μl l(-1)) and/or darkness. Darkness resulted in twofold up-regulation of ipt expression, whereas darkness combined with ethylene caused eightfold up-regulation in line 6 compared to Wt plants. The transgenic line had significantly higher content of chlorophyll at the end of the treatment period compared to Wt plants.