RESUMO
Agrobacterium-mediated transformation of epicotyl segment has been used in Citrus transgenic studies. The approach suffers, however, from limitations such as occasionally seed unavailability, the low transformation efficiency of juvenile tissues and the high frequency of chimeric plants. Therefore, a suspension cell culture system was established and used to generate transgenic plants in this study to overcome the shortcomings. The embryonic calli were successfully developed from undeveloped ovules of the three cultivars used in this study, "Sweet orange"-Egyptian cultivar (Citrus sinensis), "Shatangju" (Citrus reticulata) and "W. Murcott" (Citrus reticulata), on three different solid media. Effects of media, genotypes and ages of ovules on the induction of embryonic calli were also investigated. The result showed that the ovules' age interferes with the callus production more significantly than media and genotypes. The 8 to 10 week-old ovules were found to be the best materials. A cell suspension culture system was established in an H+H liquid medium. Transgenic plants were obtained from Agrobacterium-mediated transformation of cell suspension as long as eight weeks subculture intervals. A high transformation rate (~35%) was achieved by using our systems, confirming BASTA selection and later on by PCR confirmation. The results demonstrated that transformation of cell suspension should be more useful for the generation of non-chimeric transgenic Citrus plants. It was also shown that our cell suspension culture procedure was efficient in maintaining the vigor and regeneration potential of the cells.
RESUMO
BACKGROUND: Cotton is the world's most important natural textile fiber and a significant oilseed crop. Decoding cotton genomes will provide the ultimate reference and resource for research and utilization of the species. Integration of high-density genetic maps with genomic sequence information will largely accelerate the process of whole-genome assembly in cotton. RESULTS: In this paper, we update a high-density interspecific genetic linkage map of allotetraploid cultivated cotton. An additional 1,167 marker loci have been added to our previously published map of 2,247 loci. Three new marker types, InDel (insertion-deletion) and SNP (single nucleotide polymorphism) developed from gene information, and REMAP (retrotransposon-microsatellite amplified polymorphism), were used to increase map density. The updated map consists of 3,414 loci in 26 linkage groups covering 3,667.62 cM with an average inter-locus distance of 1.08 cM. Furthermore, genome-wide sequence analysis was finished using 3,324 informative sequence-based markers and publicly-available Gossypium DNA sequence information. A total of 413,113 EST and 195 BAC sequences were physically anchored and clustered by 3,324 sequence-based markers. Of these, 14,243 ESTs and 188 BACs from different species of Gossypium were clustered and specifically anchored to the high-density genetic map. A total of 2,748 candidate unigenes from 2,111 ESTs clusters and 63 BACs were mined for functional annotation and classification. The 337 ESTs/genes related to fiber quality traits were integrated with 132 previously reported cotton fiber quality quantitative trait loci, which demonstrated the important roles in fiber quality of these genes. Higher-level sequence conservation between different cotton species and between the A- and D-subgenomes in tetraploid cotton was found, indicating a common evolutionary origin for orthologous and paralogous loci in Gossypium. CONCLUSION: This study will serve as a valuable genomic resource for tetraploid cotton genome assembly, for cloning genes related to superior agronomic traits, and for further comparative genomic analyses in Gossypium.
