Abstract
Apomixis is a common reproduction system in the genus Citrus. To investigate the molecular mechanism of apomictic embryogenesis in Citrus, genes expressed specifically in an apomictic genotype were isolated by PCR-selected suppression subtractive hybridization with total RNAs obtained from the ovule at anthesis. Several genes showing conspicuously different expressions between polyembryonic (apomictic) and monoembryonic (nonapomictic) genotypes were selected, and their expression profiles during ovule development were analyzed in detail. This analysis identified two apomictic and three nonapomictic genotype-specific genes. Among the latter, msg-2 was highly expressed in the late stage of somatic embryogenesis. Specific expression during ovule development in monoembryonic cultivars and in the late stage of somatic embryogenesis indicated that msg-2 is not expressed in the initiation stage of polyembryogenesis and somatic embryogenesis, suggesting its role in suppressing initial cell formation of somatic embryos. The full-length complementary DNA of msg-2 contained small open reading frames in its sequence but showed no homology to functionally known genes in the public databases. As sequences similar to msg-2 were frequently found among Citrus expressed sequence tags, msg-2 may be associated with polyembryogenesis and somatic embryogenesis in a Citrus-specific manner.
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Acknowledgments
This work was supported in part by Research Fellowships of the Japan Society for the Promotion of Science for Young Scientists. The authors would like to thank Enago (www.enago.jp) for the English language review.
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Communicated by W.-W. Guo
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Supplementary Fig. 1
Full-length cDNA sequence and predicted open reading frame (ORF) structure of msg-2. ORFs longer than 100 bp in both directions are shown under the sequence. Positions of predicted first methionine and stop codon for both sense and antisense directions are indicated (JPEG 71 kb)
Supplementary Table 1
Results of homology search for 530 bp sequence of msg-2 cDNA. a)sequences ranked in the top five of BLAST searches for each database are shown (XLS 39 kb)
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Nakano, M., Kigoshi, K., Shimizu, T. et al. Characterization of genes associated with polyembryony and in vitro somatic embryogenesis in Citrus . Tree Genetics & Genomes 9, 795–803 (2013). https://doi.org/10.1007/s11295-013-0598-8
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DOI: https://doi.org/10.1007/s11295-013-0598-8