ORIGINAL ARTICLE A strong root-specific expression system for stable transgene expression in bread wheat Gang-Ping Xue 1 • Anne L. Rae 1 • Rosemary G. White 2 • Janneke Drenth 1 • Terese Richardson 2 • C. Lynne McIntyre 1 Received: 3 September 2015 / Revised: 26 October 2015 / Accepted: 3 November 2015 / Published online: 13 November 2015 Ó Springer-Verlag Berlin Heidelberg 2015 Abstract Key message A strong, stable and root-specific expression system was developed from a rice root- specific GLYCINE-RICH PROTEIN 7 promoter for use as an enabling technology for genetic manipulation of wheat root traits. Abstract Root systems play an important role in wheat productivity. Genetic manipulation of wheat root traits often requires a root-specific or root-predominant expres- sion system as an essential enabling technology. In this study, we investigated promoters from rice root-specific or root-predominant expressed genes for development of a root expression system in bread wheat. Transient expres- sion analysis using a GREEN FLUORESCENT PROTEIN (GFP) reporter gene driven by rice promoters identified six promoters that were strongly expressed in wheat roots. Extensive organ specificity analysis of three rice promoters in transgenic wheat revealed that the promoter of rice GLYCINE-RICH PROTEIN 7 (OsGRP7) gene conferred a root-specific expression pattern in wheat. Strong GFP flu- orescence in the seminal and branch roots of wheat expressing GFP reporter driven by the OsGRP7 promoter was detected in epidermal, cortical and endodermal cells in mature parts of the root. The GFP reporter driven by the promoter of rice METALLOTHIONEIN-LIKE PROTEIN 1 (OsMTL1) gene was mainly expressed in the roots with essentially no expression in the leaf, stem or seed. How- ever, it was also expressed in floral organs including glume, lemma, palea and awn. In contrast, strong expres- sion of rice RCg2 promoter-driven GFP was found in many tissues. The GFP expression driven by these three rice promoters was stable in transgenic wheat plants through three generations (T1–T3) examined. These data suggest that the OsGRP7 promoter can provide a strong, stable and root-specific expression system for use as an enabling technology for genetic manipulation of wheat root traits. Keywords Root-specific expression Á Promoter Á GFP reporter Á Transgene Á Glycine-rich protein Á Wheat Abbreviations GFP Green fluorescent protein GRP Glycine-rich protein MTL Metallothionein-like Introduction Root systems play a vital role in nutrient and water acquisition, as well as producing anti-microbial compounds against root pathogens. Improvement of root traits partic- ularly for maximising uptake of nutrients and water is an important breeding target for further increasing crop yield, particularly in unfavourable environments such as under water shortage and low nutrient soil (Wasson et al. 2012; Communicated by P. Lakshmanan. Electronic supplementary material The online version of this article (doi:10.1007/s00299-015-1897-3) contains supplementary material, which is available to authorized users. & Gang-Ping Xue gang-ping.xue@csiro.au 1 CSIRO Agriculture, 306 Carmody Rd., St Lucia, QLD 4067, Australia 2 CSIRO Agriculture, Clunies Ross Street, Canberra, ACT 2601, Australia 123 Plant Cell Rep (2016) 35:469–481 DOI 10.1007/s00299-015-1897-3