Iron partitioning at an early growth stage impacts iron deficiency responses in soybean plants (Glycine max L.).

Carla S Santos,Susana M P Carvalho,Mariana Roriz,Marta W Vasconcelos

doi:10.3389/fpls.2015.00325

Carla S Santos, Susana M P Carvalho + Show 2 more

Open Access

https://doi.org/10.3389/fpls.2015.00325

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Abstract

Iron (Fe) deficiency chlorosis (IDC) leads to leaf yellowing, stunted growth and drastic yield losses. Plants have been differentiated into ‘Fe-efficient’ (EF) if they resist to IDC and ‘Fe-inefficient’ (IN) if they do not, but the reasons for this contrasting efficiency remain elusive. We grew EF and IN soybean plants under Fe deficient and Fe sufficient conditions and evaluated if gene expression and the ability to partition Fe could be related to IDC efficiency. At an early growth stage, Fe-efficiency was associated with higher chlorophyll content, but Fe reductase activity was low under Fe-deficiency for EF and IN plants. The removal of the unifoliate leaves alleviated IDC symptoms, increased shoot:root ratio, and trifoliate leaf area. EF plants were able to translocate Fe to the aboveground plant organs, whereas the IN plants accumulated more Fe in the roots. FRO2-like gene expression was low in the roots; IRT1-like expression was higher in the shoots; and ferritin was highly expressed in the roots of the IN plants. The efficiency trait is linked to Fe partitioning and the up-regulation of Fe-storage related genes could interfere with this key process. This work provides new insights into the importance of mineral partitioning among different plant organs at an early growth stage.

Highlights

Soybean (Glycine max L.) is the highest produced legume crop, reaching production levels of about 230 million metric tons per year, across the world (Vasconcelos and Grusak, 2014)
EF plants grown in Fe sufficiency remained green throughout the experiment, while the IN ones presented some signs of chlorosis
The removal of the unifoliate leaves led to an increase in the shoot dry weight (DW) in both accessions but this was only significantly higher in the EF plants (Figure 5A)

Summary

Introduction

Soybean (Glycine max L.) is the highest produced legume crop, reaching production levels of about 230 million metric tons per year, across the world (Vasconcelos and Grusak, 2014). Since Fe is an essential element that has a key role in fundamental biological processes, such as photosynthesis and chlorophyll biosynthesis, when this micronutrient is unavailable to the plants, they frequently exhibit yellowing of the upper leaves, interveinal chlorosis, and stunted growth (Jeong and Connolly, 2009). This problem underpins the urgency to develop cultivars that can be more efficient in Fe uptake and further mineral translocation from the roots to the shoots, increasing plant nutritional value (Carvalho and Vasconcelos, 2013).

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