ELONGATED HYPOCOTYL 5 (HY5) and POPEYE (PYE) Regulate Intercellular Iron
Transport in Plants .
Abstract
Plants maintain iron (Fe) homeostasis under varying environmental
conditions by balancing processes such as Fe uptake, transport, and
storage. In Arabidopsis, POPEYE (PYE), a basic helix-loop-helix (bHLH)
transcription factor (TF), has been shown to play a crucial role in
regulating this balance. In recent years, the mechanisms regulating Fe
uptake have been well established but the upstream transcriptional
regulators of Fe transport and storage are still poorly understood. In
this study, we report that ELONGATED HYPOCOTYL5 (HY5), a basic leucine
zipper (bZIP) TF which has recently been shown to play a crucial role in
Fe homeostasis, interacts with PYE. Molecular, genetic and biochemical
approaches revealed that PYE and HY5 have overlapping as well as some
distinct roles in regulation of Fe deficiency response. We found that
HY5 and PYE both act as a repressor of Fe transport genes such as
YSL3, FRD3 NPF5.9, YSL2, NAS4, and OPT3. HY5 was found to
directly bind on the promoter of these genes and regulate intercellular
Fe transport. Further analysis revealed that HY5 and PYE directly
interact at the same region on PYE and NAS4 promoter.
Overall, this study revealed that HY5 regulates Fe homeostasis by
physically interacting with PYE as well as independently.