Abstract
Fe deficiency may increase Cd accumulation in peanuts. However, the mechanisms are not yet fully understood. In the present study, two contrasting peanut cultivars, Luhua 8 (low seed-Cd cultivar) and Zhenghong 3 (high seed-Cd cultivar) were used to investigate the effect of Fe deficiency on the uptake and accumulation of cadmium (Cd) by hydroponic experiments. Under Fe-sufficient conditions, compared with Luhua 8, Zhenghong 3 had higher specific root length (SRL) and proportion of fine roots with a lower Km for Cd and showed slightly higher expression of AhIRT1 and AhNRAMP1 in the roots. These traits may be responsible for high capacity for Cd accumulation in Zhenghong 3. Under Fe deficiency, the increase of Cd accumulation was much larger in Zhenghong 3 than in Luhua 8. Kinetics studies revealed that the Vmax for Cd influx was 1.56-fold higher in Fe-deficient plants than in Fe-sufficient plants for Zhenghong 3, versus 0.48-fold higher for Luhua 8. Moreover, the increased expression levels of AhIRT1 and AhNRAMP1 induced by Fe deficiency was higher in Zhenghong 3 than in Luhua 8. Yeast complementation assays suggested that the AhIRT1 and AhNRAMP1 may function as transporters involved in Cd uptake. In conclusion, the different Cd accumulation between the two cultivars under Fe deficiency may be correlated with Vmax value for Cd uptake and the expression levels of AhIRT1 and AhNRAMP1 in the roots.
Highlights
Iron (Fe) is an important microelement for plant growth and development
The present results showed that, the two cultivars were similar in the responses of plant growth to Fe deficiency (Fig 1A and 1B), the decreases in the active Fe content and chlorophyll contents in the leaves as a consequence of Fe deficiency were larger in Zhenghong 3 than in Luhua 8 (Fig 1C and 1D), indicating Zhenghong 3 is more sensitive to Fe deficiency compared with Luhua 8
The results indicate that increased Cd uptake by roots induced by Fe deficiency may account for higher Cd accumulation observed in Zhenghong 3
Summary
Iron (Fe) is an important microelement for plant growth and development. As a redox-active metal, Fe is involved in many physiological processes including photosynthesis, mitochondrial respiration, nitrogen assimilation, hormone biosynthesis, production and scavenging of reactive oxygen species, osmoprotection and pathogen defence [1, 2]. The total Fe content in soil regularly exceeds plant requirements, it is present as oxihydrates with low bioavailability [3], in calcareous soils, which represent 30% of the earth’s surface [4]. Fe deficiency has become a yield-limiting factor for a variety of field crops all around the world. Cadmium (Cd) is a highly toxic non-essential metal that is taken up by plant roots and transported into the aerial parts [5]. Cd is taken up by epidermal cells, radially
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