Maize Transformation Using the Morphogenic Genes Baby Boom and Wuschel2
Despite the fact that maize transformation has been available for over 25 years, the technology has remained too specialized, labor-intensive, and inefficient to be useful for the majority of academic labs. Compounding this problem, future demands in maize genome engineering will likely require a step change beyond what researchers view as “traditional” maize transformation methods. Recently, we published on our use of constitutively expressed morphogenic transcription factors Baby Boom (Bbm) and Wuschel2 (Wus2) to improve maize transformation, which requires CRE-mediated excision before regeneration of healthy, fertile T0 plants. Moving beyond this first-generation system, we have developed a new expression system for Bbm and Wus2, using a non-constitutive maize phospholipid transferase protein promoter (Pltppro) driving Bbm expression and a maize auxin-inducible promoter (Axig1pro) for WUS2 expression. Using this combination of expression cassettes, abundant somatic embryos rapidly form on the scutella of Agrobacterium-transformed zygotic immature embryos. These somatic embryos are uniformly transformed and can be directly germinated into plants without a callus phase. Transformed plants are sent to the greenhouse in as little as 1 month, and these T0 plants match the seed-derived phenotype for the inbred and are fertile. T1 seeds germinate normally and have a uniformly wild-type inbred phenotype. This new system represents a rapid, user-friendly transformation process that can potentially facilitate high-throughput production of transgenic T0 plants in B73, Mo17, and the recently developed Fast-Flowering Mini-Maize.
Key wordsMaize Transformation Bbm Wus2 PLTPpro Axig1pro Morphogenic genes
- 2.Lowe K, Wu E, Wang N, Hoerster G, Hastings C, Cho M-J, Scelonge C, Lenderts B, Chamberlin M, Cushatt J, Wang L, Ryan L, Khan T, Chow-Yiu J, Hua W, Yu M, Bahn J, Bao Z, Brink K, Igo E, Rudrappa B, Shamseer PM, Bruce W, Newman L, Shen B, Zheng P, Bidney D, Falco C, Register J, Zhao Z-Y, Xu D, Jones T, Gordon-Kamm W (2016) Morphogenic regulators Baby boom and Wuschel improve monocot transformation. Plant Cell 28:1–19CrossRefGoogle Scholar
- 4.Garnaat C, Lowe K, Roth B (2002) Zm-AXIG1-specific polynucleotides and methods of use. WO2002006499Google Scholar
- 6.Anand A, Bass SH, Cho H-J, Klein TM, Lassner M, McBride KE (2017) Methods and compositions of improved plant transformation. PCT/US2016/049132Google Scholar
- 11.Gordon-Kamm WJ, Helentjaris TG, Lowe KS, Shen B, Tarczynski MC Zheng P (2005) Ap2 domain transcription factor Odp2 (ovule development protein 2) and methods of use. Patent no. WO2005/075655-A2Google Scholar
- 14.Lowe KS, Cahoon RE, Scelong CJ, Tao Y, Gordon-Kamm WJ, Bruce WB, Newman LJ (2007) Wuschel (WUS) Gene Homologs Patent No US7256322Google Scholar