Because iron (Fe) is involved in many physiological and biochemical processes in plant cells, it is indispensable for growth and development. In rice (Oryza sativa), OsHRZ1, an Fe‐binding ubiquitin ligase, is a putative sensor of Fe homeostasis that negatively regulates iron acquisition. Despite its apparent importance, only a single basic‐Helix–Loop–Helix (bHLH) transcription factor, OsPRI1, has been identified as a direct target of OsHRZ1.
In a recent study published in Plant, Cell & Environment, researchers from XIshuangbanna Tropical Botanical Garden (XTBG) identified OsPRI2 and OsPRI3 as two paralogs of OsPRI1, both of which interact with OsHRZ1.
To verify that OsPRI2 and OsPRI3 are directly targeted by OsHRZ1, the researchers performed pull‐down experiments involving the following purified recombinant fusion proteins: GST‐HRZ1 (glutathione S‐transferase‐OsHRZ1), His‐OsPRI2 (6× histidine‐OsPRI2), and His‐OsPRI3. They applied cell‐free degradation assays to monitor the degradation of OsPRI2 and OsPRI3.
Loss‐of‐function mutations to each of the two transcription factors resulted in severe Fe‐deficiency symptoms, inhibited Fe translocation from the roots to the shoots, and downregulated expression of Fe‐deficiency‐responsive genes.
In contrast, the overexpression of these genes promoted Fe accumulation in the roots and shoots and enhanced the expression of Fe‐deficiency‐responsive genes.
Furthermore, the downstream genes OsIRO2/3 and OsYSL2 were directly regulated by OsPRI2 and OsPRI3.
“We herein reveal that the overexpression of a single gene (OsPRI2 or OsPRI3) is sufficient to activate the expression of downstream genes associated with Fe uptake. Therefore, the application of OsPRI2 or OsPRI3 may be useful for developing Fe‐efficient and Fe‐fortified plants for improved food and biomass production”, said Prof. LIANG Gang, principal investigator of the study.
“Our results provide insights into the complex network regulating Fe homeostasis in rice”, added Prof. LIANG.
LAING Gang Ph.D Principal Investigator
Key Laboratory of Tropical Plant Resources and Sustainable Use, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun 666303, Yunnan, China