Fig. 4

Expression levels (FPKM) of asparagine synthetase genes TaASN1, TaASN2, TaASN3.1, TaASN3.2 and TaASN4, in the embryo and endosperm of developing grain from two wheat (Triticum aestivum) genotypes, Spark and SR3. The plants were grown with sulphur either supplied (+) or withheld (−). Results for each homeologue are shown separately, as indicated. a Embryo, 14 dpa. b Endosperm, 14 dpa. c Embryo, 21 dpa. d Endosperm, 21 dpa. Gene reference numbers are given in Additional file 2. The increase in expression of the TaASN1 homeologue on chromosome 5D in response to sulphur deficiency in SR3 embryo at 21 dpa was significant (p = 0.0478), as was the increase in expression of both TaASN2 homeologues (p = 0.038 and 0.047 for the 3A and 3D homeologues, respectively). The reduction of expression of the two TaASN2 homeologues at 21 dpa in the endosperm in response to sulphur deficiency was also significant (p < 0.001 for both), as was the increase in expression of the 5A and 5D TaASN1 homeologues (p < 0.001 and p = 0.0012, respectively)