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Root ABA Accumulation Enhances Rice Seedling Drought Tolerance under Ammonium Supply: Interaction with Aquaporins

View Article: PubMed Central - PubMed

ABSTRACT

In previous studies, we demonstrated that ammonium nutrition enhances the drought tolerance of rice seedlings compared to nitrate nutrition and contributes to a higher root water uptake ability. It remains unclear why rice seedlings maintain a higher water uptake ability when supplied with ammonium under drought stress. Here, we focused on the effects of nitrogen form and drought stress on root abscisic acid (ABA) concentration and aquaporin expression using hydroponics experiments and stimulating drought stress with 10% PEG6000. Drought stress decreased the leaf photosynthetic rate and stomatal conductivity and increased the leaf temperature of plants supplied with either ammonium or nitrate, but especially under nitrate supply. After 4 h of PEG treatment, the root protoplast water permeability and the expression of root PIP and TIP genes decreased in plants supplied with ammonium or nitrate. After 24 h of PEG treatment, the root hydraulic conductivity, the protoplast water permeability, and the expression of some aquaporin genes increased in plants supplied with ammonium compared to those under non-PEG treatment. Root ABA accumulation was induced by 24 h of PEG treatment, especially in plants supplied with ammonium. The addition of exogenous ABA decreased the expression of PIP and TIP genes under non-PEG treatment but increased the expression of some of them under PEG treatment. We concluded that drought stress induced a down-regulation of aquaporin expression, which appeared earlier than did root ABA accumulation. With continued drought stress, aquaporin expression and activity increased due to root ABA accumulation in plants supplied with ammonium.

No MeSH data available.


Effects of different nitrogen forms and drought stress on root hydraulic conductivity (A) and the root protoplast water permeability coefficient Pos(B,C). Root hydraulic conductivity was measured after 24 h of PEG treatment. Root protoplasts were isolated after 4 h (B) and 24 h (C) of PEG treatment. The data represent the means of four replicates. The error bars indicate the ±SD. Significant differences (P < 0.05) between treatments are indicated by different letters. Rice seedlings were supplied with ammonium or nitrate under control and drought stress stimulation by adding 10% PEG6000 (NH4+ + PEG as ANP; NO3- + PEG as NNP).
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Figure 3: Effects of different nitrogen forms and drought stress on root hydraulic conductivity (A) and the root protoplast water permeability coefficient Pos(B,C). Root hydraulic conductivity was measured after 24 h of PEG treatment. Root protoplasts were isolated after 4 h (B) and 24 h (C) of PEG treatment. The data represent the means of four replicates. The error bars indicate the ±SD. Significant differences (P < 0.05) between treatments are indicated by different letters. Rice seedlings were supplied with ammonium or nitrate under control and drought stress stimulation by adding 10% PEG6000 (NH4+ + PEG as ANP; NO3- + PEG as NNP).

Mentions: After 24 h of PEG treatment, the root hydraulic conductivity increased significantly in plants supplied with NH4+. Compared to non-PEG treatment, drought stress enhanced the root hydraulic conductivity approximately twofold when the plants were fed NH4+ (Figure 3A). Similar results were not observed in plants supplied with NO3-.


Root ABA Accumulation Enhances Rice Seedling Drought Tolerance under Ammonium Supply: Interaction with Aquaporins
Effects of different nitrogen forms and drought stress on root hydraulic conductivity (A) and the root protoplast water permeability coefficient Pos(B,C). Root hydraulic conductivity was measured after 24 h of PEG treatment. Root protoplasts were isolated after 4 h (B) and 24 h (C) of PEG treatment. The data represent the means of four replicates. The error bars indicate the ±SD. Significant differences (P < 0.05) between treatments are indicated by different letters. Rice seedlings were supplied with ammonium or nitrate under control and drought stress stimulation by adding 10% PEG6000 (NH4+ + PEG as ANP; NO3- + PEG as NNP).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4979525&req=5

Figure 3: Effects of different nitrogen forms and drought stress on root hydraulic conductivity (A) and the root protoplast water permeability coefficient Pos(B,C). Root hydraulic conductivity was measured after 24 h of PEG treatment. Root protoplasts were isolated after 4 h (B) and 24 h (C) of PEG treatment. The data represent the means of four replicates. The error bars indicate the ±SD. Significant differences (P < 0.05) between treatments are indicated by different letters. Rice seedlings were supplied with ammonium or nitrate under control and drought stress stimulation by adding 10% PEG6000 (NH4+ + PEG as ANP; NO3- + PEG as NNP).
Mentions: After 24 h of PEG treatment, the root hydraulic conductivity increased significantly in plants supplied with NH4+. Compared to non-PEG treatment, drought stress enhanced the root hydraulic conductivity approximately twofold when the plants were fed NH4+ (Figure 3A). Similar results were not observed in plants supplied with NO3-.

View Article: PubMed Central - PubMed

ABSTRACT

In previous studies, we demonstrated that ammonium nutrition enhances the drought tolerance of rice seedlings compared to nitrate nutrition and contributes to a higher root water uptake ability. It remains unclear why rice seedlings maintain a higher water uptake ability when supplied with ammonium under drought stress. Here, we focused on the effects of nitrogen form and drought stress on root abscisic acid (ABA) concentration and aquaporin expression using hydroponics experiments and stimulating drought stress with 10% PEG6000. Drought stress decreased the leaf photosynthetic rate and stomatal conductivity and increased the leaf temperature of plants supplied with either ammonium or nitrate, but especially under nitrate supply. After 4 h of PEG treatment, the root protoplast water permeability and the expression of root PIP and TIP genes decreased in plants supplied with ammonium or nitrate. After 24 h of PEG treatment, the root hydraulic conductivity, the protoplast water permeability, and the expression of some aquaporin genes increased in plants supplied with ammonium compared to those under non-PEG treatment. Root ABA accumulation was induced by 24 h of PEG treatment, especially in plants supplied with ammonium. The addition of exogenous ABA decreased the expression of PIP and TIP genes under non-PEG treatment but increased the expression of some of them under PEG treatment. We concluded that drought stress induced a down-regulation of aquaporin expression, which appeared earlier than did root ABA accumulation. With continued drought stress, aquaporin expression and activity increased due to root ABA accumulation in plants supplied with ammonium.

No MeSH data available.