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Genome duplication improves rice root resistance to salt stress.

Tu Y, Jiang A, Gan L, Hossain M, Zhang J, Peng B, Xiong Y, Song Z, Cai D, Xu W, Zhang J, He Y - Rice (N Y) (2014)

Bottom Line: We found that tetraploid rice showed less root growth inhibition, accumulated higher proline content and lower MDA content, and exhibited a higher frequency of normal epidermal cells than diploid rice.Furthermore, Na(+) in tetraploid rice roots significantly decreased while root tip H(+) efflux in tetraploid rice significantly increased.Our results suggest that genome duplication improves root resistance to salt stress, and that enhanced proton transport to the root surface may play a role in reducing Na(+) entrance into the roots.

View Article: PubMed Central - HTML - PubMed

Affiliation: Hubei Collaborative Innovation Center for Green Transformation of Bio-Resources, Hubei University, Wuhan 430062, P.R. China.

ABSTRACT

Background: Salinity is a stressful environmental factor that limits the productivity of crop plants, and roots form the major interface between plants and various abiotic stresses. Rice is a salt-sensitive crop and its polyploid shows advantages in terms of stress resistance. The objective of this study was to investigate the effects of genome duplication on rice root resistance to salt stress.

Results: Both diploid rice (HN2026-2x and Nipponbare-2x) and their corresponding tetraploid rice (HN2026-4x and Nipponbare-4x) were cultured in half-strength Murashige and Skoog medium with 150 mM NaCl for 3 and 5 days. Accumulations of proline, soluble sugar, malondialdehyde (MDA), Na(+) content, H(+) (proton) flux at root tips, and the microstructure and ultrastructure in rice roots were examined. We found that tetraploid rice showed less root growth inhibition, accumulated higher proline content and lower MDA content, and exhibited a higher frequency of normal epidermal cells than diploid rice. In addition, a protective gap appeared between the cortex and pericycle cells in tetraploid rice. Next, ultrastructural analysis showed that genome duplication improved membrane, organelle, and nuclei stability. Furthermore, Na(+) in tetraploid rice roots significantly decreased while root tip H(+) efflux in tetraploid rice significantly increased.

Conclusions: Our results suggest that genome duplication improves root resistance to salt stress, and that enhanced proton transport to the root surface may play a role in reducing Na(+) entrance into the roots.

No MeSH data available.


Related in: MedlinePlus

Root ultrastructure of Nipponbare-2x and Nipponbare-4x under salt stress (Bar in E = 0.2 μm; others bars = 0.5 μm). (A) The epidermis cells with abundant cytoplasm (arrow) in the diploid without NaCl treatment. (A1) The epidermis cells in tetraploid rice were similar to the diploid under normal conditions. Arrow indicates abundant cytoplasm. (B) After NaCl treatment for 3 days the cell wall of the epidermis cells became loose (arrow). (B1) The cell wall of epidermis cells in Nipponbare-4x became thicker and formed a barrier around the cells (arrow). (C) Floccules (arrow) were discovered between the epidermis cells in Nipponbare-2x. (C1) The epidermis cells were normal in Nipponbare-4x, and the arrow shows normal abundant cytoplasm. (D) Membrane organelles were indicative of evident transfiguration (arrow) in the pericycle cells of Nipponbare-2x. (D1) Pericycle cells maintained a normal shape surrounded by cytoplasm (arrow) in Nipponbare-4x. (E) The nuclei with an abnormal shape, whereby floccule nuclear cytoplasm was observed in the pericycle cells of Nipponbare-2x (arrow). (E1) Nuclei with intact membrane (arrow) and dispersed chromatins were observed in pericycle cells of Nipponbare-4x.
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Figure 6: Root ultrastructure of Nipponbare-2x and Nipponbare-4x under salt stress (Bar in E = 0.2 μm; others bars = 0.5 μm). (A) The epidermis cells with abundant cytoplasm (arrow) in the diploid without NaCl treatment. (A1) The epidermis cells in tetraploid rice were similar to the diploid under normal conditions. Arrow indicates abundant cytoplasm. (B) After NaCl treatment for 3 days the cell wall of the epidermis cells became loose (arrow). (B1) The cell wall of epidermis cells in Nipponbare-4x became thicker and formed a barrier around the cells (arrow). (C) Floccules (arrow) were discovered between the epidermis cells in Nipponbare-2x. (C1) The epidermis cells were normal in Nipponbare-4x, and the arrow shows normal abundant cytoplasm. (D) Membrane organelles were indicative of evident transfiguration (arrow) in the pericycle cells of Nipponbare-2x. (D1) Pericycle cells maintained a normal shape surrounded by cytoplasm (arrow) in Nipponbare-4x. (E) The nuclei with an abnormal shape, whereby floccule nuclear cytoplasm was observed in the pericycle cells of Nipponbare-2x (arrow). (E1) Nuclei with intact membrane (arrow) and dispersed chromatins were observed in pericycle cells of Nipponbare-4x.

Mentions: Ultrastructural analysis in Nipponbare-2x and -4x cultivars roots under 150 mM NaCl stress for 3 and 5 days showed that genome duplication improved rice adaptability, including the epidermis cell protective mechanism, membrane organelle, and nuclei stability. The epidermis cells with abundant cytoplasm accumulation around the cell wall were closely connected in diploid and tetraploid rice without salt treatment (Figure 6A, A1). After treatment with NaCl for 3 days, the cell wall of the epidermis cells became loose, and some exterior parts of the epidermis cell wall were isolated and desquamated in Nipponbare-2x (Figure 6B). However, in Nipponbare-4x, the epidermis cell wall became thicker and a barrier formed around the epidermis cells (Figure 6B, B1). A significant difference was observed for the cortex cells between Nipponbare-2x and Nipponbare-4x. Floccules were discovered between the cortex cells in Nipponbare-2x (Figure 6C), which was not observed in Nipponbare-4x (Figure 6Cl). Membrane organelles showed an evident transfiguration in the pericycle cells of Nipponbare-2x (Figure 6D). In contrast, cells maintained their normal shape surrounded by cytoplasm in Nipponbare-4x (Figure 6D1). After NaCl treatment for 5 days, nuclei with an abnormal shape and floccule nuclear cytoplasm were observed in the pericycle cells of Nipponbare-2x (Figure 6E). However, nuclei with intact membranes, smooth surfaces, and dispersed chromatin were observed in Nipponbare-4x (Figure 6E1). These results indicated that genome duplication promoted roots to show normal active metabolism.


Genome duplication improves rice root resistance to salt stress.

Tu Y, Jiang A, Gan L, Hossain M, Zhang J, Peng B, Xiong Y, Song Z, Cai D, Xu W, Zhang J, He Y - Rice (N Y) (2014)

Root ultrastructure of Nipponbare-2x and Nipponbare-4x under salt stress (Bar in E = 0.2 μm; others bars = 0.5 μm). (A) The epidermis cells with abundant cytoplasm (arrow) in the diploid without NaCl treatment. (A1) The epidermis cells in tetraploid rice were similar to the diploid under normal conditions. Arrow indicates abundant cytoplasm. (B) After NaCl treatment for 3 days the cell wall of the epidermis cells became loose (arrow). (B1) The cell wall of epidermis cells in Nipponbare-4x became thicker and formed a barrier around the cells (arrow). (C) Floccules (arrow) were discovered between the epidermis cells in Nipponbare-2x. (C1) The epidermis cells were normal in Nipponbare-4x, and the arrow shows normal abundant cytoplasm. (D) Membrane organelles were indicative of evident transfiguration (arrow) in the pericycle cells of Nipponbare-2x. (D1) Pericycle cells maintained a normal shape surrounded by cytoplasm (arrow) in Nipponbare-4x. (E) The nuclei with an abnormal shape, whereby floccule nuclear cytoplasm was observed in the pericycle cells of Nipponbare-2x (arrow). (E1) Nuclei with intact membrane (arrow) and dispersed chromatins were observed in pericycle cells of Nipponbare-4x.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
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Figure 6: Root ultrastructure of Nipponbare-2x and Nipponbare-4x under salt stress (Bar in E = 0.2 μm; others bars = 0.5 μm). (A) The epidermis cells with abundant cytoplasm (arrow) in the diploid without NaCl treatment. (A1) The epidermis cells in tetraploid rice were similar to the diploid under normal conditions. Arrow indicates abundant cytoplasm. (B) After NaCl treatment for 3 days the cell wall of the epidermis cells became loose (arrow). (B1) The cell wall of epidermis cells in Nipponbare-4x became thicker and formed a barrier around the cells (arrow). (C) Floccules (arrow) were discovered between the epidermis cells in Nipponbare-2x. (C1) The epidermis cells were normal in Nipponbare-4x, and the arrow shows normal abundant cytoplasm. (D) Membrane organelles were indicative of evident transfiguration (arrow) in the pericycle cells of Nipponbare-2x. (D1) Pericycle cells maintained a normal shape surrounded by cytoplasm (arrow) in Nipponbare-4x. (E) The nuclei with an abnormal shape, whereby floccule nuclear cytoplasm was observed in the pericycle cells of Nipponbare-2x (arrow). (E1) Nuclei with intact membrane (arrow) and dispersed chromatins were observed in pericycle cells of Nipponbare-4x.
Mentions: Ultrastructural analysis in Nipponbare-2x and -4x cultivars roots under 150 mM NaCl stress for 3 and 5 days showed that genome duplication improved rice adaptability, including the epidermis cell protective mechanism, membrane organelle, and nuclei stability. The epidermis cells with abundant cytoplasm accumulation around the cell wall were closely connected in diploid and tetraploid rice without salt treatment (Figure 6A, A1). After treatment with NaCl for 3 days, the cell wall of the epidermis cells became loose, and some exterior parts of the epidermis cell wall were isolated and desquamated in Nipponbare-2x (Figure 6B). However, in Nipponbare-4x, the epidermis cell wall became thicker and a barrier formed around the epidermis cells (Figure 6B, B1). A significant difference was observed for the cortex cells between Nipponbare-2x and Nipponbare-4x. Floccules were discovered between the cortex cells in Nipponbare-2x (Figure 6C), which was not observed in Nipponbare-4x (Figure 6Cl). Membrane organelles showed an evident transfiguration in the pericycle cells of Nipponbare-2x (Figure 6D). In contrast, cells maintained their normal shape surrounded by cytoplasm in Nipponbare-4x (Figure 6D1). After NaCl treatment for 5 days, nuclei with an abnormal shape and floccule nuclear cytoplasm were observed in the pericycle cells of Nipponbare-2x (Figure 6E). However, nuclei with intact membranes, smooth surfaces, and dispersed chromatin were observed in Nipponbare-4x (Figure 6E1). These results indicated that genome duplication promoted roots to show normal active metabolism.

Bottom Line: We found that tetraploid rice showed less root growth inhibition, accumulated higher proline content and lower MDA content, and exhibited a higher frequency of normal epidermal cells than diploid rice.Furthermore, Na(+) in tetraploid rice roots significantly decreased while root tip H(+) efflux in tetraploid rice significantly increased.Our results suggest that genome duplication improves root resistance to salt stress, and that enhanced proton transport to the root surface may play a role in reducing Na(+) entrance into the roots.

View Article: PubMed Central - HTML - PubMed

Affiliation: Hubei Collaborative Innovation Center for Green Transformation of Bio-Resources, Hubei University, Wuhan 430062, P.R. China.

ABSTRACT

Background: Salinity is a stressful environmental factor that limits the productivity of crop plants, and roots form the major interface between plants and various abiotic stresses. Rice is a salt-sensitive crop and its polyploid shows advantages in terms of stress resistance. The objective of this study was to investigate the effects of genome duplication on rice root resistance to salt stress.

Results: Both diploid rice (HN2026-2x and Nipponbare-2x) and their corresponding tetraploid rice (HN2026-4x and Nipponbare-4x) were cultured in half-strength Murashige and Skoog medium with 150 mM NaCl for 3 and 5 days. Accumulations of proline, soluble sugar, malondialdehyde (MDA), Na(+) content, H(+) (proton) flux at root tips, and the microstructure and ultrastructure in rice roots were examined. We found that tetraploid rice showed less root growth inhibition, accumulated higher proline content and lower MDA content, and exhibited a higher frequency of normal epidermal cells than diploid rice. In addition, a protective gap appeared between the cortex and pericycle cells in tetraploid rice. Next, ultrastructural analysis showed that genome duplication improved membrane, organelle, and nuclei stability. Furthermore, Na(+) in tetraploid rice roots significantly decreased while root tip H(+) efflux in tetraploid rice significantly increased.

Conclusions: Our results suggest that genome duplication improves root resistance to salt stress, and that enhanced proton transport to the root surface may play a role in reducing Na(+) entrance into the roots.

No MeSH data available.


Related in: MedlinePlus