Fig. 1

Schematic of the inducible Cre-Lox system. a The initial construct contains Cre recombinase (red), under the control of a stress inducible promoter, such as pHvHSP17 (red), and a constitutive expression promoter, here the maize Ubiquitin promoter (pZmUbi, black), driving expression of a reporter gene (blue) followed by an appropriate terminator (grey). The reporter gene is flanked by two loxP recombination sites (green triangles) and is followed by a second gene of interest (GOI; yellow) which is not expressed in the initial construct. b Following application of stress, in this case a heat shock treatment, expression of the Cre recombinase gene is induced. c The Cre recombinase protein carries out recombination at the loxP sites flanking the reporter gene. d Following excision of the reporter gene, the gene of interest is now in frame with the promoter sequence, and expression of the gene of interest is now under the control of the constitutive promoter. e A heat shock inducible construct, HS_GFP, utilised the barley HvHSP17 promoter to drive expression of Cre recombinase following heat shock, leading to irreversible excision of the reporter gene, mCHERRY, and induction of eGFP. f This system has also been established in wheat, using GUS as the reporter gene which when excised leads to expression of NAM-B1. The loxP cassette is inverted in the wheat construct, relative to its position in the barley construct