Background: Legumes comprise important crops that offer major agronomic benefits, including the capacity of establishing symbiosis with rhizobia, fixing atmospheric N2. It has been proven that legumes are particularly susceptible to boron (B) stress, which leads to important yield penalties. Boron (B) deficiency or toxicity in plants causes the inhibition of growth and an altered development. Under such conditions, the participation of two distinct protein families (the major intrinsic protein family MIP and the Boron transporter family BOR) is required to minimize detrimental effects caused by B stress. However, in legumes, little is known about the transport mechanisms responsible for B uptake and distribution, especially under deficiency.
Results: A Medicago truncatula protein, MtNIP5;1 (Medtr1g097840) (homologous to the Arabidopsis thaliana AtNIP5;1) was identified as a novel legume B transporter involved in B uptake under deficiency. Further analyses revealed that this M. truncatula aquaporin expression was boron-regulated in roots, being induced under deficiency and repressed under toxicity. It localizes at the plasma membrane of root epidermal cells and in nodules, where B plays pivotal roles in symbiosis. Furthermore, the partial complementation of the nip5;1-1 A. thaliana mutant phenotype under B deficiency supports a functional role of MtNIP5;1 as a B transporter in this legume model plant.
Conclusions: The results here presented support a functional role of MtNIP5;1 in B uptake under deficiency and provides new insights into B transport mechanisms in legume species.

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On 22 Nov, 2020
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Posted 30 Oct, 2020
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Received 28 Sep, 2020
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On 24 Sep, 2020
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On 09 Jul, 2020
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Invitations sent on 01 Jul, 2020
On 16 Jun, 2020
On 15 Jun, 2020
On 15 Jun, 2020
On 15 Jun, 2020
On 22 Nov, 2020
On 19 Nov, 2020
Posted 30 Oct, 2020
On 15 Nov, 2020
On 23 Oct, 2020
On 22 Oct, 2020
On 22 Oct, 2020
On 20 Oct, 2020
Received 28 Sep, 2020
Received 28 Sep, 2020
On 25 Sep, 2020
Invitations sent on 24 Sep, 2020
On 24 Sep, 2020
On 23 Sep, 2020
On 22 Sep, 2020
On 21 Sep, 2020
Received 23 Jul, 2020
On 23 Jul, 2020
Received 13 Jul, 2020
On 09 Jul, 2020
On 06 Jul, 2020
Invitations sent on 01 Jul, 2020
On 16 Jun, 2020
On 15 Jun, 2020
On 15 Jun, 2020
On 15 Jun, 2020
Background: Legumes comprise important crops that offer major agronomic benefits, including the capacity of establishing symbiosis with rhizobia, fixing atmospheric N2. It has been proven that legumes are particularly susceptible to boron (B) stress, which leads to important yield penalties. Boron (B) deficiency or toxicity in plants causes the inhibition of growth and an altered development. Under such conditions, the participation of two distinct protein families (the major intrinsic protein family MIP and the Boron transporter family BOR) is required to minimize detrimental effects caused by B stress. However, in legumes, little is known about the transport mechanisms responsible for B uptake and distribution, especially under deficiency.
Results: A Medicago truncatula protein, MtNIP5;1 (Medtr1g097840) (homologous to the Arabidopsis thaliana AtNIP5;1) was identified as a novel legume B transporter involved in B uptake under deficiency. Further analyses revealed that this M. truncatula aquaporin expression was boron-regulated in roots, being induced under deficiency and repressed under toxicity. It localizes at the plasma membrane of root epidermal cells and in nodules, where B plays pivotal roles in symbiosis. Furthermore, the partial complementation of the nip5;1-1 A. thaliana mutant phenotype under B deficiency supports a functional role of MtNIP5;1 as a B transporter in this legume model plant.
Conclusions: The results here presented support a functional role of MtNIP5;1 in B uptake under deficiency and provides new insights into B transport mechanisms in legume species.

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6
This is a list of supplementary files associated with this preprint. Click to download.
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