Ectopic expression of a truncated Pinus radiata AGAMOUS homolog (PrAG1) causes alteration of inflorescence architecture and male sterility in Nicotiana tabacum
Plant MADS-box genes of the AG/PLE subfamily control the identity of sexual organs. An AG-homologous gene (PrAG1) was characterized in the Pinus radiata genome. PrAG1 transcript was detected only in the female and male strobili. To investigate its regulatory function during floral development, three binary vectors were constructed and transformed into tobacco plants for overexpression of the PrAG1 full-length protein (35S::MIKC), and truncated proteins with deletion of C domain (35S::MIK) or deletion of both C and K domains (35S::MI) under control of the CaMV 35S promoter. All transgenic tobacco lines with ectopic expression of 35S::MIKC and 35S::MIK showed no phenotypic effect on floral development. However, 23.8% of the 35S::MI transgenic lines displayed altered inflorescence architecture and variety of floral development changes, including complete male sterility, suggesting that PrAG1 may be the P. radiata AG-homologous gene with C-function and that it may play a role in the determination of meristem identities in both inflorescence and flowering. Expression of truncated AG MI genes could be useful in reducing plant pollen and seed formation, as well as increasing inflorescence branching and flower production, providing a novel engineered sterility strategy for transgenic plants with potential commercial application in molecular breeding of horticultural flowering plants.
KeywordsAgamous Inflorescence architecture MADS-box gene Nicotiana tabacum Pinus radiata Transgenic sterility
This research was supported in part by Canadian Forest Service. The author thanks the late Drs. D. F. Karnosky and G. K. Podila for their support and help in initiation of the project. This manuscript was prepared in memory of their great contribution to forest biotechnology.
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