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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

The longest root microstructure, diameter, and abnormal epidermis frequency of Nipponbare-2x and Nipponbare-4x under salt stress (Bar = 50 μm).(A) Roots of Nipponbare-2x under normal conditions. (A1) Roots of Nipponbare-4x under normal conditions. (B) Root of Nipponbare-2x under salt stress for 3 days, whereby the black arrows show the epidermis cells abnormally shelled. (B1) Root of Nipponbare-4x under salt stress for 3 days, whereby the epidermis cells maintained a normal station and the black arrow shows regularly thicker endodermis cells. (C) Roots of Nipponbare-2x under salt stress for 5 days, whereby the root shrank and transfigured; the black arrow suggests that the epidermis became thinner. (C1) Root of Nipponbare-4x under salt stress for 5 days, whereby the protective gap formed between the cortex cells and pericycle cells (white arrow) and the epidermis cells became much thicker (black arrow) and were in close contact with each other. (D) Diameter of the longest root; (E) Frequency of roots with abnormal epidermis cells under salt stress.
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Figure 5: The longest root microstructure, diameter, and abnormal epidermis frequency of Nipponbare-2x and Nipponbare-4x under salt stress (Bar = 50 μm).(A) Roots of Nipponbare-2x under normal conditions. (A1) Roots of Nipponbare-4x under normal conditions. (B) Root of Nipponbare-2x under salt stress for 3 days, whereby the black arrows show the epidermis cells abnormally shelled. (B1) Root of Nipponbare-4x under salt stress for 3 days, whereby the epidermis cells maintained a normal station and the black arrow shows regularly thicker endodermis cells. (C) Roots of Nipponbare-2x under salt stress for 5 days, whereby the root shrank and transfigured; the black arrow suggests that the epidermis became thinner. (C1) Root of Nipponbare-4x under salt stress for 5 days, whereby the protective gap formed between the cortex cells and pericycle cells (white arrow) and the epidermis cells became much thicker (black arrow) and were in close contact with each other. (D) Diameter of the longest root; (E) Frequency of roots with abnormal epidermis cells under salt stress.

Mentions: To increase our understanding of the root response in polyploid rice, the anatomical structure of roots in Nipponbare-2x and -4x cultivars were observed on plants under salt stress for 3 and 5 days because Nipponbare-4x was thought to be more resistant to salt. Histological analysis indicated that genome duplication regulated the root response to salt stress. The root microstructure in diploid and tetraploid rice was similar without salt stress, and no evident morphological differences in the epidermis, cortex, vascular system, or aerenchyma were observed to facilitate oxygen transport. However, the diameter of the longest root in tetraploid rice was larger than that in the corresponding diploid (Figure 5A, A1, D). Following 3 days of stress at 150 mM NaCl, evident epidermis cell transfigurations were detected in Nipponbare-2x. For example, it became thinner and 57.89% of roots showed some epidermis cells that were shelled. However, 82.75% of the investigated roots indicated the epidermis cells in Nipponbare-4x maintained the normal framework and became thicker (Figure 5B, B1, E). Continuous morphological analysis after the root was exposed to 150 mM NaCl for 5 days revealed distinct differences between diploid and tetraploid rice (Figure 5C, C1). The roots in Nipponbare-2x shrank and became transfigured because of the extended water absence under salt stress; 78.54% of epidermis cells in the investigated roots brushed off and more aerenchyma tissues were produced by the cortex cells compared to 3-day roots under salt stress(Figure 5E). In addition, the pericycle cells shrank (Figure 5C, E), while in the roots of Nipponbare-4x, only 22.34% of epidermis cells separated from the cortex cell. Obvious thicker epidermis cells were in tight contact, and endo-epidermis formed a thicker barrier protected from the aerenchyma damage and blocked deleterious ion transport to pericycle cells. The protective gap produced between the cortex cells and pericycle cells, as well as the neighboring cells of pericycle cells, were thicker, which was considered the second barrier for the root in Nipponbare-4x. The root response in HN2026-2x and HN2026-4x was similar to Nipponbare-2x and Nipponbare-4x, respectively (data not shown).


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)

The longest root microstructure, diameter, and abnormal epidermis frequency of Nipponbare-2x and Nipponbare-4x under salt stress (Bar = 50 μm).(A) Roots of Nipponbare-2x under normal conditions. (A1) Roots of Nipponbare-4x under normal conditions. (B) Root of Nipponbare-2x under salt stress for 3 days, whereby the black arrows show the epidermis cells abnormally shelled. (B1) Root of Nipponbare-4x under salt stress for 3 days, whereby the epidermis cells maintained a normal station and the black arrow shows regularly thicker endodermis cells. (C) Roots of Nipponbare-2x under salt stress for 5 days, whereby the root shrank and transfigured; the black arrow suggests that the epidermis became thinner. (C1) Root of Nipponbare-4x under salt stress for 5 days, whereby the protective gap formed between the cortex cells and pericycle cells (white arrow) and the epidermis cells became much thicker (black arrow) and were in close contact with each other. (D) Diameter of the longest root; (E) Frequency of roots with abnormal epidermis cells under salt stress.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
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Figure 5: The longest root microstructure, diameter, and abnormal epidermis frequency of Nipponbare-2x and Nipponbare-4x under salt stress (Bar = 50 μm).(A) Roots of Nipponbare-2x under normal conditions. (A1) Roots of Nipponbare-4x under normal conditions. (B) Root of Nipponbare-2x under salt stress for 3 days, whereby the black arrows show the epidermis cells abnormally shelled. (B1) Root of Nipponbare-4x under salt stress for 3 days, whereby the epidermis cells maintained a normal station and the black arrow shows regularly thicker endodermis cells. (C) Roots of Nipponbare-2x under salt stress for 5 days, whereby the root shrank and transfigured; the black arrow suggests that the epidermis became thinner. (C1) Root of Nipponbare-4x under salt stress for 5 days, whereby the protective gap formed between the cortex cells and pericycle cells (white arrow) and the epidermis cells became much thicker (black arrow) and were in close contact with each other. (D) Diameter of the longest root; (E) Frequency of roots with abnormal epidermis cells under salt stress.
Mentions: To increase our understanding of the root response in polyploid rice, the anatomical structure of roots in Nipponbare-2x and -4x cultivars were observed on plants under salt stress for 3 and 5 days because Nipponbare-4x was thought to be more resistant to salt. Histological analysis indicated that genome duplication regulated the root response to salt stress. The root microstructure in diploid and tetraploid rice was similar without salt stress, and no evident morphological differences in the epidermis, cortex, vascular system, or aerenchyma were observed to facilitate oxygen transport. However, the diameter of the longest root in tetraploid rice was larger than that in the corresponding diploid (Figure 5A, A1, D). Following 3 days of stress at 150 mM NaCl, evident epidermis cell transfigurations were detected in Nipponbare-2x. For example, it became thinner and 57.89% of roots showed some epidermis cells that were shelled. However, 82.75% of the investigated roots indicated the epidermis cells in Nipponbare-4x maintained the normal framework and became thicker (Figure 5B, B1, E). Continuous morphological analysis after the root was exposed to 150 mM NaCl for 5 days revealed distinct differences between diploid and tetraploid rice (Figure 5C, C1). The roots in Nipponbare-2x shrank and became transfigured because of the extended water absence under salt stress; 78.54% of epidermis cells in the investigated roots brushed off and more aerenchyma tissues were produced by the cortex cells compared to 3-day roots under salt stress(Figure 5E). In addition, the pericycle cells shrank (Figure 5C, E), while in the roots of Nipponbare-4x, only 22.34% of epidermis cells separated from the cortex cell. Obvious thicker epidermis cells were in tight contact, and endo-epidermis formed a thicker barrier protected from the aerenchyma damage and blocked deleterious ion transport to pericycle cells. The protective gap produced between the cortex cells and pericycle cells, as well as the neighboring cells of pericycle cells, were thicker, which was considered the second barrier for the root in Nipponbare-4x. The root response in HN2026-2x and HN2026-4x was similar to Nipponbare-2x and Nipponbare-4x, respectively (data not shown).

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