Transcript profiling of maize NCEDs and ZEPs in kernel at 40 and 60 DAP. qRT-PCR was performed on total RNA of the indicated tissues using gene-specific primers listed in Additional file 2. Gene codes are detailed in Table 4. RNA quality and quantity were checked by total RNA loading on an agarose gel and ethidium bromide staining. Transcript levels were normalized with the values obtained for the Zeastar gene, which was used as an internal reference gene, and are shown relative to NCED3 transcript levels in embryo at 40 DAP (the expression level of maize NCED3 in embryo at 40 DAP = 1). Values represent the mean of three biological replicates ± SE. When two samples show different letters above the bars, the difference between them is significant (P < 0.05). When both tissue and genotype effects were significant, a, b, λ a and λ b are indicated (see the Methods section and ANOVA in Additional file 4). End X: endosperm at x DAP; Emb X: embryo at X DAP.