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In order to investigate chromosome elimination in symmetric somatic hybridization between Bupleurum scorzonerifolium and Arabidopsis thaliana, protoplasts were isolated from suspension cultures of both A. thaliana and B. scorzonerifolium parents. Biparental protoplasts were mixed at a rate of 1.5:1 and fused with PEG-method. After protoplast fusion, the products were cultured in the P5 liquid medium for microcallus formation. Single cell lines formed from microcalli after subculturing on the MB1 (Xia and Chen, Plant Sci 120:197–203, 1996) solid medium. The putative somatic hybrid cell lines were identified by cytological and molecular analysis. Of the 132 somatic cell lines generated, 16 were identified as somatic hybrids, with the phenotypes resembled B. scorzonerifolium parent. These hybrids showed a complete set of B. scorzonerifolium chromosome and 0–2 small chromosome(s) of A. thaliana. A few of them showed nuclear and cytoplasmic SSR fragments of A. thaliana. These hybrid cell lines could differentiate to green spots, buds/leaves through complementation of regeneration ability. The chromosomes elimination of A. thaliana was discussed.

The protoplasts of Arabidopsis thaliana (L.) Heynh. treated with 7.5 mM of IOA (iodoacetoamide) were fused with those of Bupleurum scorzonerifolium Willd, using PEG-mediated method. The protoplasts of B. scorzonerifolium were irradiated with ultraviolet light (UV) at an intensity of 380 μW/cm 2 for 30, 60, 90, and 120 s, respectively, before fusion. In cell clones produced in all the fusion combinations, only those from Combination VI (UV 120 s) differentiated to plantlets. The cell lines and plantlets were identified as somatic hybrids by analysis of chromosome size and number, RAPD, 5S rDNA spacer sequence respectively. Genomic in situ hybridization (GISH) revealed that there was a complete set of chromosomes of donor ( B. scorzonerifolium ) in all hybrids with a few intact chromosomes and chromosome segment(s) of recipient ( A. thaliana ) in the hybrid cell lines from Combinations I–V or only chromosomal segment(s) in the regenerated cell lines from Combination VI. The numbers of chromosomal fragments from A. thaliana translocated or inserted to donor chromosomes increased with UV dose enhanced. The UV-tolerance of B. scorzonerifolium and indirect effect of UV on the exclusion and introgression of receptor ( A. thaliana ) chromosomes in the hybrid cells was discussed.

LIM homeobox family members regulate a variety of cell fate choices during animal development. In C. elegans, mutations in the LIM homeobox gene lin-11 have previously been shown to alter the cell division pattern of a subset of the 2° lineage vulval cells. We demonstrate multiple functions of lin-11 during vulval development. We examined the fate of vulval cells in lin-11 mutant animals using five cellular markers and found that lin-11 is necessary for the patterning of both 1° and 2° lineage cells. In the absence of lin-11 function, vulval cells fail to acquire correct identity and inappropriately fuse with each other. The expression pattern of lin-11 reveals dynamic changes during development. Using a temporally controlled overexpression system, we show that lin-11 is initially required in vulval cells for establishing the correct invagination pattern. This process involves asymmetric expression of lin-11 in the 2° lineage cells. Using a conditional RNAi approach, we show that lin-11 regulates vulval morphogenesis. Finally, we show that LDB-1, a NLI/Ldb1/CLIM2 family member, interacts physically with LIN-11, and is necessary for vulval morphogenesis. Together, these findings demonstrate that temporal regulation of lin-11 is crucial for the wild-type vulval patterning.