The iron deficiency signal transmits from shoot to root, and activates transcription factors OsIDEF1 and OsIRO2, which in turn modulates the downstream targets involved in Fe homeostasis at the transcriptional level, leading to Fe uptake and accumulation
in roots. In contrast, Fe deficiency inhibited BR biosynthesis, and the reduced endogenous BRs may facilitate Fe transport and translocation from roots to shoots. The exogenous application of EBR to rice seedlings would suppress the transport and translocation of Fe from roots to shoots, thus leading to a more severe phenotype of Fe deficiency in
shoots and strengthen Fe deficiency signal. The enhanced
signal of Fe deficiency will further upregulate downstream
genes involved in Fe homeostasis, and lead to Fe uptake and
accumulation in roots. BRs negatively regulated Fe transport
and translocation from root to shoot in rice seedlings, but the
mechanisms are not clear. Therefore, future research focusing
on the interaction of BR with Fe transport and translocation
in strategy II plants is warranted.