The bHLH Transcription Factor PhbHLH121 Regulates Response to Iron Deficiency in <i>Petunia hybrida</i>
2024
Liru Pan | Chengcheng Huang | Ruiling Li | Yanbang Li
Iron (Fe) is an essential micronutrient for plants. Due to the low Fe bioavailability in cultivated soils, Fe deficiency is a widespread agricultural problem. In this study, we present the functional characterization of a petunia (<i>Petunia hybrida</i>) basic-helix-loop-helix transcription factor PhbHLH121 in response to Fe shortage. Real-time PCR revealed that the expression of <i>PhbHLH121</i> in petunia roots and shoots was downregulated under Fe-limited conditions. CRISPR/Cas9-edited <i>phbhlh121</i> mutant plants were generated to investigate the functions of PhbHLH121 in petunia. Loss-of-function of PhbHLH121 enhanced petunia tolerance to Fe deficiency. Further investigations revealed that the expression level of several structural genes involved in Fe uptake in petunia, such as <i>IRT1</i> and <i>FRO2</i>, was higher in <i>phbhlh121</i> mutants compared to that in wild-type under Fe-limited conditions, and the expression level of several genes involved in Fe storage and Fe transport, such as <i>VTL2</i>, <i>FERs</i> and <i>ZIF1</i>, was lower in <i>phbhlh121</i> mutants compared to that in wild-type under Fe-deficient conditions. Yeast one-hybrid assays revealed that PhbHLH121 binds to the G-box element in the promoter of genes involved in Fe homeostasis. Yeast two-hybrid assays revealed that PhbHLH121 interacts with petunia bHLH IVc proteins. Taken together, PhbHLH121 plays an important role in the Fe deficiency response in petunia.
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