Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2020 Oct 11;9(10):1341.
doi: 10.3390/plants9101341.

Drought-Induced Responses of Nitrogen Metabolism in Ipomoea batatas

Houqiang Xia  1 , Tao Xu  1 , Jing Zhang  1 , Ke Shen  1 , Zongyun Li  1 , Jingran Liu  1
Affiliations

Drought-Induced Responses of Nitrogen Metabolism in Ipomoea batatas

Houqiang Xia et al. Plants (Basel). .

Abstract

This study investigated the effect of water stress, simulated by the polyethylene glycol (PEG-6000) method, on nitrogen (N) metabolism in leaves and roots of hydroponically grown sweet potato seedlings, Xushu 32 (X32) and Ningzishu 1 (N1). The concentrations of PEG-6000 treatments were 0%, 5% and 10% (m/v). The results showed that the drought-treated plants showed a decline leaf relative water content, and revealed severe growth inhibition, compared with the 0% treatment. Under drought stress, the decline in biomass of the leaf and stem was more noticeable than in root biomass for X32, leading to a higher root to shoot ratio. Drought stress increased the nitrate nitrogen (NO3--N) and protein in leaves, but reduced all the activities of N-metabolism enzymes and the transcriptional levels of nitrate reductase (NR), glutamine synthetase (GS) and glutamate synthase (GOGAT); in roots, NO3--N and NR had opposite trends. The leaf ammonium nitrogen (NH4+-N), GS and amino acid had different trends between X32 and N1 under drought stress. Furthermore, the transcriptional level of nitrate transporter genes NRT1.1 in leaves and roots were upregulated under drought stress, except in N1 roots. In conclusion, NR determined the different response to drought in leaves for X32 and N1, and GS and GOGAT determined the response to drought in roots, respectively.

Keywords: Ipomoea batatas sweet potato; ammonium uptake and accumulation; drought stress; gene transcription; nitrate uptake.

PubMed Disclaimer

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Effects of drought stress on relative water content (RWC) and the membrane stability index (MSI) in sweet potato leaves. X32 and N1 represent Xushu 32 and Ningzishu 1, respectively.
Figure 2
Figure 2
Correlation analysis between relative water content (RWC) and membrane stability index (MSI) in sweet potato leaves. n = 24, R20.05 = 0.164, and R20.01 = 0.265.
Figure 3
Figure 3
Effect of PEG-induced drought stress on plant growth and development in the sweet potato. Each treatment consisted of five pots, each containing twelve plants. X32 and N1 represent Xushu 32 and Ningzishu 1, respectively.
Figure 4
Figure 4
Growth parameters of sweet potato seedlings as affected by the different PEG concentrations. X32 and N1 represent Xushu 32 and Ningzishu 1, respectively. Values followed by the different lowercase letters within the same cultivar in the main part are significantly different (p < 0.05) among the three PEG levels for leaf, stem and root biomass, and by the different big letters within the same cultivar in the main part are significantly different for plant biomass. Values followed by different small letters within the same cultivar in the input part are significantly different (p < 0.05) among the three PEG levels for X32, and by different capital letters for N1.
Figure 5
Figure 5
Effects of drought stress on chlorophyll content (A: Chl a content; B: Chl b content; C: Total Chl content; D: Chl a/b ratio) in sweet potato leaves. X32 and N1 represent Xushu 32 and Ningzishu 1, respectively. The stages labeled with an asterisk (*) indicate significant differences (p < 0.05) among the three PEG levels in the figure.
Figure 6
Figure 6
Effects of drought stress on NO3−-N and NH4+-N content in leaves (A,C) and roots (B,D) of the sweet potato. X32 and N1 represent Xushu 32 and Ningzishu 1, respectively. The stages labeled with an asterisk (*) indicate significant differences (p < 0.05) among the three PEG levels in the figure.
Figure 7
Figure 7
Effects of drought stress on the NH4+/NO3− ratio in leaves and roots of the sweet potato. X32 and N1 represent Xushu 32 and Ningzishu 1, respectively. Different letters in the same cultivar indicate significant differences (p < 0.05) among the three PEG levels in the figure.
Figure 8
Figure 8
Effects of drought stress on amino acid and soluble protein content in leaves (A,C) and roots (B,D) of sweet potato. X32 and N1 represent Xushu 32 and Ningzishu 1, respectively. The stages labeled with an asterisk (*) indicate significant differences (p < 0.05) among the three PEG levels in the figure.
Figure 9
Figure 9
Relationship between NO3−-N, NH4+-N, amino acid or the soluble protein content with leaf relative water content in leaves (A–D) and roots (E–H) for the two sweet potatoes. The solid and dotted lines represent X32 and N1, respectively.
Figure 10
Figure 10
Effects of drought stress on NR activity and GS activity in leaves (A,C) and roots (B,D) of the sweet potato. X32 and N1 represent Xushu 32 and Ningzishu 1, respectively. The stages labeled with an asterisk (*) indicate significant differences (p < 0.05) among the three PEG levels in the figure.
Figure 11
Figure 11
Effects of drought stress on GOGAT activity and GDH activity in leaves (A,C) and roots (B,D) of the sweet potato. X32 and N1 represent Xushu 32 and Ningzishu 1, respectively. The stages labeled with an asterisk (*) indicate significant differences (p < 0.05) among the three PEG levels in the figure.
Figure 12
Figure 12
Relationship between NR, GS, GOGAT or GDH activities with the leaf relative water content in leaves (A–D) and roots (E–H) for the two sweet potato. The solid and dotted lines represent X32 and N1, respectively.
Figure 13
Figure 13
Effects of drought stress on the transcription of N metabolism-related genes in leaves and roots of two sweet potato cultivars. Sweet potato seedlings were subjected to 5 days of drought stress (10% PEG); total RNA was isolated from leaves and roots for real-time PCR analysis. X32 and N1 represent Xushu 32 and Ningzishu 1, respectively. The stages labeled with an asterisk (*) indicate significant differences (p < 0.05) between the 0% and 10% PEG levels in the figure.
Figure 14
Figure 14
A model of the N regulation in sweet potato seedlings in response to drought stress. Here, drought stress stimulates a N-mediated tandem reaction, which improves the sweet potato drought tolerance. Reducing leaf RWC might alter the expression levels of key regulatory metabolic genes and the activities of N metabolism enzymes, which in turn modulates N accumulation, activates the transcription of NO3− transporters to regulate sugar allocation to adapt to environmental stress. Upregulated items under drought stress are marked with red, downregulated items under PEG-induced drought stress are marked with blue, and items that do not change significantly under PEG-induced drought stress are marked with grey.
See this image and copyright information in PMC

References

    1. Ma D., Li Q., Cao Q., Niu F., Xie Y., Tang J., Li H. Development and prospect of sweetpotato industry and its technologies in China. Jiangsu J. Agric. Sci. 2012;28:969–973. (In Chinese)
    1. Ruan L., Chen L., Chen Y., He J., Zhang W., Gao Z., Zhang Y. Expression of Arabidopsis HOMEODOMAIN GLABROUS 11 enhances tolerance to drought stress in transgenic sweet potato plants. J. Plant Biol. 2012;55:151–158. doi: 10.1007/s12374-011-9198-z. - DOI
    1. Zhai H., Wang F., Si Z., Huo J., Xing L., An Y., He S., Liu Q. A myo-inositol-1-phosphate synthase gene, IbMIPS1, enhances salt and drought tolerance and stem nematode resistance in transgenic sweet potato. Plant Biotechnol. J. 2016;14:592–602. doi: 10.1111/pbi.12402. - DOI - PMC - PubMed
    1. Wang B.Q., Du Z.H., Xie B.T., Zhang H.Y., Zhang L.M., Zhang W.L. Effects of film mulching on water content in soil and root formation of summer sweet potato seedlings. Shangdong Agric. Sci. 2014;46:41–45+51. (In Chinese)
    1. Jiang Z., Lv Y. High yield cultivation technology of sweet potato. Rain Fed Crops. 2010;30:225–226. (In Chinese)

LinkOut - more resources