Iron (Fe) deficiency has become a widespread agricultural problem, because Fe deficiency reduces plant growth, crop yield, and crop quality. Plants take up Fe from the soil by roots. About one-third of worldwide cultivated land belongs to calcareous soils where Fe availability is very low. Thus, breeding plants with strong Fe-uptake ability has been suggested as a good approach to improve crop yield in calcareous soils. 

Researchers from Xishuangbanna Tropical Botanical Garden (XTBG)  of the Chinese Academy of Sciences attempted to improve the plants' tolerance of Arabidopsis to Fe deficiency under Fe-deficiency conditions.  

They selected three different Fe-deficiency responsive promoters (Pro_IRT1, Pro_MYB72, and Pro_bHLH100) to drive the expression of a bHLH104-GFP fusion gene. The corresponding transgenic plants were generated. 

Their experiments showed that overexpression of Fe deficiency responsive genes, IRT1, MYB72, or bHLH100, caused enhanced sensitivity to Fe deficiency. ProIRT1:bHLH104-GFP plants showed the enhanced sensitivity to Fe deficiency on Fe-deficient media and the reduced fertility in alkaline soil.  

In contrast, ProbHLH100:bHLH104-GFP plants displayed a slight tolerance to Fe deficiency and Pro_MYB72:bHLH104-GFP plants had a significant advantage in growth in alkaline soil, including increased root length, chlorophyll, and biomass. 

In the alkaline soil, ProMYB72:bHLH104-GFP had higher seed yield and Fe concentration than other plants analyzed.  

The study reveals that the expression of bHLH104-GFP driven by Fe-responsive promoters conferred superior growth, high seed yield, and high seed Fe concentration under Fe-deficiency conditions in Arabidopsis. It provides a candidate strategy for breeding Fe-deficiency tolerant plants. 

The study entitled "Fe-deficiency-induced expression of bHLH104 enhances Fe-deficiency tolerance of Arabidopsis thaliana" has been published online in Planta.