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) attempted to improve the plants’ tolerance of Arabidopsis to Fe deficiency under Fe-deficiency conditions. They selected three different Fe-deficiency responsive promoters (ProIRT1, ProMYB72, and ProbHLH100) 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 ProMYB72: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.