TY - JOUR
T1 - Glucocorticoid receptor-regulated TcLEC2 expression triggers somatic embryogenesis in Theobroma cacao leaf tissue
AU - Fister, Andrew S.
AU - Landherr, Lena
AU - Perryman, Melanie
AU - Zhang, Yufan
AU - Guiltinan, Mark J.
AU - Maximova, Siela N.
N1 - Publisher Copyright:
© 2018 Fister et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
PY - 2018/11
Y1 - 2018/11
N2 - Theobroma cacao, the source of cocoa, is a crop of particular importance in many developing countries. Availability of elite planting material is a limiting factor for increasing productivity of Theobroma cacao; therefore, the development of new strategies for clonal propagation is essential to improve farmers’ incomes and to meet increasing global demand for cocoa. To develop a more efficient embryogenesis system for cacao, tissue was transformed with a transgene encoding a fusion of Leafy Cotyledon 2 (TcLEC2) to a glucocorticoid receptor domain (GR) to control nuclear localization of the protein. Upon application of the glucocorticoid dexamethasone (dex), downstream targets of LEC2 involved in seed-development were up-regulated and somatic embryos (SEs) were successfully regenerated from TcLEC2-GR transgenic flower and leaf tissue in large numbers. Immature SEs regenerated from TcLEC2-GR leaves were smaller in size than immature SEs from floral tissue, suggesting a different ontogenetic origin. Additionally, exposure of TcLEC2-GR floral explants to dex increased the number of SEs compared to floral explants from control, non-transgenic trees or from TcLEC2-GR floral explants not treated with dex. Testing different durations of exposure to dex indicated that a three-day treatment produced optimal embryo regeneration. Leaf derived SEs were successfully grown to maturity, converted into plants, and established in the greenhouse, demonstrating that these embryos are fully developmentally competent. In summary, we demonstrate that regulating TcLEC2 activity offers a powerful new strategy for optimizing somatic embryogenesis pipelines for cacao.
AB - Theobroma cacao, the source of cocoa, is a crop of particular importance in many developing countries. Availability of elite planting material is a limiting factor for increasing productivity of Theobroma cacao; therefore, the development of new strategies for clonal propagation is essential to improve farmers’ incomes and to meet increasing global demand for cocoa. To develop a more efficient embryogenesis system for cacao, tissue was transformed with a transgene encoding a fusion of Leafy Cotyledon 2 (TcLEC2) to a glucocorticoid receptor domain (GR) to control nuclear localization of the protein. Upon application of the glucocorticoid dexamethasone (dex), downstream targets of LEC2 involved in seed-development were up-regulated and somatic embryos (SEs) were successfully regenerated from TcLEC2-GR transgenic flower and leaf tissue in large numbers. Immature SEs regenerated from TcLEC2-GR leaves were smaller in size than immature SEs from floral tissue, suggesting a different ontogenetic origin. Additionally, exposure of TcLEC2-GR floral explants to dex increased the number of SEs compared to floral explants from control, non-transgenic trees or from TcLEC2-GR floral explants not treated with dex. Testing different durations of exposure to dex indicated that a three-day treatment produced optimal embryo regeneration. Leaf derived SEs were successfully grown to maturity, converted into plants, and established in the greenhouse, demonstrating that these embryos are fully developmentally competent. In summary, we demonstrate that regulating TcLEC2 activity offers a powerful new strategy for optimizing somatic embryogenesis pipelines for cacao.
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U2 - 10.1371/journal.pone.0207666
DO - 10.1371/journal.pone.0207666
M3 - Article
C2 - 30475838
AN - SCOPUS:85057208015
SN - 1932-6203
VL - 13
JO - PloS one
JF - PloS one
IS - 11
M1 - e0207666
ER -