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Differentially expressed membrane transporters in rice roots may contribute to cultivar dependent salt tolerance.

Senadheera P, Singh RK, Maathuis FJ - J. Exp. Bot. (2009)

Bottom Line: Physiological studies indicate that FL478 shows a lower Na(+) influx, a reduced Na(+) translocation to the shoot, and maintains a lower Na(+):K(+) ratio.However, transcripts for cation transport proteins including OsCHX11, OsCNGC1, OsCAX, and OsTPC1 showed differential regulation between the cultivars.The encoded proteins are likely to participate in reducing Na(+) influx, lowering the tissue Na(+):K(+) ratio and limiting the apoplastic bypass flow in roots of FL478 and are therefore important new targets to improve salt tolerance in rice.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant Science, University of Colombo, Colombo, Sri Lanka.

ABSTRACT
Salinity tolerance in rice, like in other glycophytes, is a function of cellular ion homeostasis. The large divergence in ion homeostasis between the salt-tolerant FL478 and salt-sensitive IR29 rice varieties can be exploited to understand mechanisms of salinity tolerance. Physiological studies indicate that FL478 shows a lower Na(+) influx, a reduced Na(+) translocation to the shoot, and maintains a lower Na(+):K(+) ratio. To understand the basis of these differences, a comparative investigation of transcript regulation in roots of the two cultivars was undertaken. This analysis revealed that genes encoding aquaporins, a silicon transporter, and N transporters are induced in both cultivars. However, transcripts for cation transport proteins including OsCHX11, OsCNGC1, OsCAX, and OsTPC1 showed differential regulation between the cultivars. The encoded proteins are likely to participate in reducing Na(+) influx, lowering the tissue Na(+):K(+) ratio and limiting the apoplastic bypass flow in roots of FL478 and are therefore important new targets to improve salt tolerance in rice.

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Related in: MedlinePlus

Relative growth rate (RGR) and rate of photosynthesis (RPS) in FL478 (FL) and IR29 (IR) after exposure to salt treatment. (A) Fifteen-day-old rice seedlings were exposed to salt treatment of 50 mM and 100 mM NaCl in hydroponic medium. RGR was measured after 12 d of salt treatment for the various tissues. (B) RPS was measured in the youngest fully expanded leaf after being exposed to 50 mM and 100 mM NaCl treatments for 12 d. Bars in (A) and (B) represent the mean ±SD of three replicates with six readings each for RPS measurements. Different letters indicate significant differences at P <0.05.
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fig1: Relative growth rate (RGR) and rate of photosynthesis (RPS) in FL478 (FL) and IR29 (IR) after exposure to salt treatment. (A) Fifteen-day-old rice seedlings were exposed to salt treatment of 50 mM and 100 mM NaCl in hydroponic medium. RGR was measured after 12 d of salt treatment for the various tissues. (B) RPS was measured in the youngest fully expanded leaf after being exposed to 50 mM and 100 mM NaCl treatments for 12 d. Bars in (A) and (B) represent the mean ±SD of three replicates with six readings each for RPS measurements. Different letters indicate significant differences at P <0.05.

Mentions: Previous studies (Walia et al., 2005, 2007) and our current results show that FL478 (FL) and IR29 (IR) exhibit discrete differences in many physiological parameters when exposed to salt stress. The most obvious is the significantly greater relative growth rate of FL (Fig. 1) which is particularly apparent in FL roots. Elongation of roots in the presence of salinity as seen in FL may be a stress-avoidance strategy where roots grow away from surface layers that tend to accumulate high levels of salts. Other parameters such as relative growth and photosynthetic rates, although negatively affected in both cultivars, remained higher in FL (Fig. 1) while maintaining a relatively low stomatal conductance compared to IR.


Differentially expressed membrane transporters in rice roots may contribute to cultivar dependent salt tolerance.

Senadheera P, Singh RK, Maathuis FJ - J. Exp. Bot. (2009)

Relative growth rate (RGR) and rate of photosynthesis (RPS) in FL478 (FL) and IR29 (IR) after exposure to salt treatment. (A) Fifteen-day-old rice seedlings were exposed to salt treatment of 50 mM and 100 mM NaCl in hydroponic medium. RGR was measured after 12 d of salt treatment for the various tissues. (B) RPS was measured in the youngest fully expanded leaf after being exposed to 50 mM and 100 mM NaCl treatments for 12 d. Bars in (A) and (B) represent the mean ±SD of three replicates with six readings each for RPS measurements. Different letters indicate significant differences at P <0.05.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2692005&req=5

fig1: Relative growth rate (RGR) and rate of photosynthesis (RPS) in FL478 (FL) and IR29 (IR) after exposure to salt treatment. (A) Fifteen-day-old rice seedlings were exposed to salt treatment of 50 mM and 100 mM NaCl in hydroponic medium. RGR was measured after 12 d of salt treatment for the various tissues. (B) RPS was measured in the youngest fully expanded leaf after being exposed to 50 mM and 100 mM NaCl treatments for 12 d. Bars in (A) and (B) represent the mean ±SD of three replicates with six readings each for RPS measurements. Different letters indicate significant differences at P <0.05.
Mentions: Previous studies (Walia et al., 2005, 2007) and our current results show that FL478 (FL) and IR29 (IR) exhibit discrete differences in many physiological parameters when exposed to salt stress. The most obvious is the significantly greater relative growth rate of FL (Fig. 1) which is particularly apparent in FL roots. Elongation of roots in the presence of salinity as seen in FL may be a stress-avoidance strategy where roots grow away from surface layers that tend to accumulate high levels of salts. Other parameters such as relative growth and photosynthetic rates, although negatively affected in both cultivars, remained higher in FL (Fig. 1) while maintaining a relatively low stomatal conductance compared to IR.

Bottom Line: Physiological studies indicate that FL478 shows a lower Na(+) influx, a reduced Na(+) translocation to the shoot, and maintains a lower Na(+):K(+) ratio.However, transcripts for cation transport proteins including OsCHX11, OsCNGC1, OsCAX, and OsTPC1 showed differential regulation between the cultivars.The encoded proteins are likely to participate in reducing Na(+) influx, lowering the tissue Na(+):K(+) ratio and limiting the apoplastic bypass flow in roots of FL478 and are therefore important new targets to improve salt tolerance in rice.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant Science, University of Colombo, Colombo, Sri Lanka.

ABSTRACT
Salinity tolerance in rice, like in other glycophytes, is a function of cellular ion homeostasis. The large divergence in ion homeostasis between the salt-tolerant FL478 and salt-sensitive IR29 rice varieties can be exploited to understand mechanisms of salinity tolerance. Physiological studies indicate that FL478 shows a lower Na(+) influx, a reduced Na(+) translocation to the shoot, and maintains a lower Na(+):K(+) ratio. To understand the basis of these differences, a comparative investigation of transcript regulation in roots of the two cultivars was undertaken. This analysis revealed that genes encoding aquaporins, a silicon transporter, and N transporters are induced in both cultivars. However, transcripts for cation transport proteins including OsCHX11, OsCNGC1, OsCAX, and OsTPC1 showed differential regulation between the cultivars. The encoded proteins are likely to participate in reducing Na(+) influx, lowering the tissue Na(+):K(+) ratio and limiting the apoplastic bypass flow in roots of FL478 and are therefore important new targets to improve salt tolerance in rice.

Show MeSH
Related in: MedlinePlus