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Two Groups of Thellungiella salsuginea RAVs Exhibit Distinct Responses and Sensitivity to Salt and ABA in Transgenic Arabidopsis.

Yang S, Luo C, Song Y, Wang J - PLoS ONE (2016)

Bottom Line: Under normal conditions, the germination process of all TsRAVs overexpressing transgenic seeds was inhibited with a stronger effect observed in 35S:A-TsRAVs seeds than in 35S:B-TsRAVs seeds.All 35S:TsRAVs transgenic plants showed a similar degree of reduction in root growth compared with untreated seedlings in the presence of ABA.Taken together, our results suggest that two groups of TsRAVs perform distinct regulating roles during plant growth and abiotic defense including drought and salt, and A-TsRAVs are more likely than B-TsRAVs to act as negative regulators in the above-mentioned biological processes.

View Article: PubMed Central - PubMed

Affiliation: School of Environmental Science and Engineering, Tianjin University, Tianjin, 300072, China.

ABSTRACT
Containing both AP2 domain and B3 domain, RAV (Related to ABI3/VP1) transcription factors are involved in diverse functions in higher plants. A total of eight TsRAV genes were isolated from the genome of Thellungiella salsuginea and could be divided into two groups (A- and B-group) based on their sequence similarity. The mRNA abundance of all Thellungiella salsuginea TsRAVs followed a gradual decline during seed germination. In Thellungiella salsuginea seedling, transcripts of TsRAVs in the group A (A-TsRAVs) were gradually and moderately reduced by salt treatment but rapidly and severely repressed by ABA treatment. In comparison, with a barely detectable constitutive expression, the transcriptional level of TsRAVs in the group B (B-TsRAVs) exhibited a moderate induction in cotyledons when confronted with ABA. We then produced the "gain-of-function" transgenic Arabidopsis plants for each TsRAV gene and found that only 35S:A-TsRAVs showed weak growth retardation including reduced root elongation, suggesting their roles in negatively controlling plant growth. Under normal conditions, the germination process of all TsRAVs overexpressing transgenic seeds was inhibited with a stronger effect observed in 35S:A-TsRAVs seeds than in 35S:B-TsRAVs seeds. With the presence of NaCl, seed germination and seedling root elongation of all plants including wild type and 35S:TsRAVs plants were retarded and a more severe inhibition occurred to the 35S:A-TsRAV transgenic plants. ABA treatment only negatively affected the germination rates of 35S:A-TsRAV transgenic seeds but not those of 35S:B-TsRAV transgenic seeds. All 35S:TsRAVs transgenic plants showed a similar degree of reduction in root growth compared with untreated seedlings in the presence of ABA. Furthermore, the cotyledon greening/expansion was more severely inhibited 35S:A-TsRAVs than in 35S:B-TsRAVs seedlings. Upon water deficiency, with a wider opening of stomata, 35S:A-TsRAVs plants experienced a faster transpirational water loss than wild type and 35S:B-TsRAVs lines. Taken together, our results suggest that two groups of TsRAVs perform distinct regulating roles during plant growth and abiotic defense including drought and salt, and A-TsRAVs are more likely than B-TsRAVs to act as negative regulators in the above-mentioned biological processes.

No MeSH data available.


Related in: MedlinePlus

NaCl sensitivity of 35S:TsRAVs transgenic Arabidopsis plants.(A) Germination rates of 35S:TsRAVs transgenic Arabidopsis seeds on 1/2 MS media with 100 mM NaCl. Each data bar represents the means ± SE of three replicates. More than 100 seeds were measured in each replicate. (B) Inhibitory effect of 100 mM NaCl on 35S:TsRAVs transgenic Arabidopsis seed germination rates. Each data bar represents the mean ± SE of three replicates. More than 50 seedlings were measured in each replicate. Different letters indicate significant differences among means (P<0.05 by Tukey’s test). (C) Inhibitory effect of 200 mM NaCl on 35S:TsRAVs transgenic Arabidopsis seedling root elongation. Seedlings were grown on normal media for 5 days before being transferred onto 1/2 MS medium with 200 mM NaCl and grown for other 6 days. Each data bar represents the mean ± SE of three replicates. More than 50 seedlings were measured in each replicate. Different letters indicate significant differences among means (P<0.05 by Tukey’s test)
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pone.0153517.g004: NaCl sensitivity of 35S:TsRAVs transgenic Arabidopsis plants.(A) Germination rates of 35S:TsRAVs transgenic Arabidopsis seeds on 1/2 MS media with 100 mM NaCl. Each data bar represents the means ± SE of three replicates. More than 100 seeds were measured in each replicate. (B) Inhibitory effect of 100 mM NaCl on 35S:TsRAVs transgenic Arabidopsis seed germination rates. Each data bar represents the mean ± SE of three replicates. More than 50 seedlings were measured in each replicate. Different letters indicate significant differences among means (P<0.05 by Tukey’s test). (C) Inhibitory effect of 200 mM NaCl on 35S:TsRAVs transgenic Arabidopsis seedling root elongation. Seedlings were grown on normal media for 5 days before being transferred onto 1/2 MS medium with 200 mM NaCl and grown for other 6 days. Each data bar represents the mean ± SE of three replicates. More than 50 seedlings were measured in each replicate. Different letters indicate significant differences among means (P<0.05 by Tukey’s test)

Mentions: Salts at high concentration could inhibit the germination of Arabidopsis and ABA plays a role in this process [42]. When wild type and transgenic seeds were germinated on media containing 50, 75 or 100 mM NaCl, all types of TsRAVs transgenic seeds experienced a considerable reduction in their germination rates (S3 Fig and Fig 4). However, the inhibitory effect of A-TsRAVs overexpression on seed germination was much more significant than that of B-TsRAVs overexpression (S3 Fig and Fig 4). At DPI 3 when nearly all WT seeds were germinated on the salt-containing media, the germination rates of B-TsRAVs and A-TsRAVs transgenic seeds reached 60% and 20%, respectively (Fig 4A and 4B), indicating that as negative regulators of seed germination process, A-TsRAVs were much more competent than B-TsRAVs. A previous work by Li and co-workers also reported that the inhibition effect of NaCl on the germination of RAV transgenic seeds was greater than on that of wild type seeds, although that they did not detect any significant difference in their germination rates on normal 1/2 MS medium [18]. In summary, our data showed that overexpression of RAV genes did not enhance the salt tolerance of transgenic plants at the seed germination stage, which was contrary to the report that pepper RAV1 improved salt tolerance when overexpressed in transgenic Arabidopsis lines [10].


Two Groups of Thellungiella salsuginea RAVs Exhibit Distinct Responses and Sensitivity to Salt and ABA in Transgenic Arabidopsis.

Yang S, Luo C, Song Y, Wang J - PLoS ONE (2016)

NaCl sensitivity of 35S:TsRAVs transgenic Arabidopsis plants.(A) Germination rates of 35S:TsRAVs transgenic Arabidopsis seeds on 1/2 MS media with 100 mM NaCl. Each data bar represents the means ± SE of three replicates. More than 100 seeds were measured in each replicate. (B) Inhibitory effect of 100 mM NaCl on 35S:TsRAVs transgenic Arabidopsis seed germination rates. Each data bar represents the mean ± SE of three replicates. More than 50 seedlings were measured in each replicate. Different letters indicate significant differences among means (P<0.05 by Tukey’s test). (C) Inhibitory effect of 200 mM NaCl on 35S:TsRAVs transgenic Arabidopsis seedling root elongation. Seedlings were grown on normal media for 5 days before being transferred onto 1/2 MS medium with 200 mM NaCl and grown for other 6 days. Each data bar represents the mean ± SE of three replicates. More than 50 seedlings were measured in each replicate. Different letters indicate significant differences among means (P<0.05 by Tukey’s test)
© Copyright Policy
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getmorefigures.php?uid=PMC4836749&req=5

pone.0153517.g004: NaCl sensitivity of 35S:TsRAVs transgenic Arabidopsis plants.(A) Germination rates of 35S:TsRAVs transgenic Arabidopsis seeds on 1/2 MS media with 100 mM NaCl. Each data bar represents the means ± SE of three replicates. More than 100 seeds were measured in each replicate. (B) Inhibitory effect of 100 mM NaCl on 35S:TsRAVs transgenic Arabidopsis seed germination rates. Each data bar represents the mean ± SE of three replicates. More than 50 seedlings were measured in each replicate. Different letters indicate significant differences among means (P<0.05 by Tukey’s test). (C) Inhibitory effect of 200 mM NaCl on 35S:TsRAVs transgenic Arabidopsis seedling root elongation. Seedlings were grown on normal media for 5 days before being transferred onto 1/2 MS medium with 200 mM NaCl and grown for other 6 days. Each data bar represents the mean ± SE of three replicates. More than 50 seedlings were measured in each replicate. Different letters indicate significant differences among means (P<0.05 by Tukey’s test)
Mentions: Salts at high concentration could inhibit the germination of Arabidopsis and ABA plays a role in this process [42]. When wild type and transgenic seeds were germinated on media containing 50, 75 or 100 mM NaCl, all types of TsRAVs transgenic seeds experienced a considerable reduction in their germination rates (S3 Fig and Fig 4). However, the inhibitory effect of A-TsRAVs overexpression on seed germination was much more significant than that of B-TsRAVs overexpression (S3 Fig and Fig 4). At DPI 3 when nearly all WT seeds were germinated on the salt-containing media, the germination rates of B-TsRAVs and A-TsRAVs transgenic seeds reached 60% and 20%, respectively (Fig 4A and 4B), indicating that as negative regulators of seed germination process, A-TsRAVs were much more competent than B-TsRAVs. A previous work by Li and co-workers also reported that the inhibition effect of NaCl on the germination of RAV transgenic seeds was greater than on that of wild type seeds, although that they did not detect any significant difference in their germination rates on normal 1/2 MS medium [18]. In summary, our data showed that overexpression of RAV genes did not enhance the salt tolerance of transgenic plants at the seed germination stage, which was contrary to the report that pepper RAV1 improved salt tolerance when overexpressed in transgenic Arabidopsis lines [10].

Bottom Line: Under normal conditions, the germination process of all TsRAVs overexpressing transgenic seeds was inhibited with a stronger effect observed in 35S:A-TsRAVs seeds than in 35S:B-TsRAVs seeds.All 35S:TsRAVs transgenic plants showed a similar degree of reduction in root growth compared with untreated seedlings in the presence of ABA.Taken together, our results suggest that two groups of TsRAVs perform distinct regulating roles during plant growth and abiotic defense including drought and salt, and A-TsRAVs are more likely than B-TsRAVs to act as negative regulators in the above-mentioned biological processes.

View Article: PubMed Central - PubMed

Affiliation: School of Environmental Science and Engineering, Tianjin University, Tianjin, 300072, China.

ABSTRACT
Containing both AP2 domain and B3 domain, RAV (Related to ABI3/VP1) transcription factors are involved in diverse functions in higher plants. A total of eight TsRAV genes were isolated from the genome of Thellungiella salsuginea and could be divided into two groups (A- and B-group) based on their sequence similarity. The mRNA abundance of all Thellungiella salsuginea TsRAVs followed a gradual decline during seed germination. In Thellungiella salsuginea seedling, transcripts of TsRAVs in the group A (A-TsRAVs) were gradually and moderately reduced by salt treatment but rapidly and severely repressed by ABA treatment. In comparison, with a barely detectable constitutive expression, the transcriptional level of TsRAVs in the group B (B-TsRAVs) exhibited a moderate induction in cotyledons when confronted with ABA. We then produced the "gain-of-function" transgenic Arabidopsis plants for each TsRAV gene and found that only 35S:A-TsRAVs showed weak growth retardation including reduced root elongation, suggesting their roles in negatively controlling plant growth. Under normal conditions, the germination process of all TsRAVs overexpressing transgenic seeds was inhibited with a stronger effect observed in 35S:A-TsRAVs seeds than in 35S:B-TsRAVs seeds. With the presence of NaCl, seed germination and seedling root elongation of all plants including wild type and 35S:TsRAVs plants were retarded and a more severe inhibition occurred to the 35S:A-TsRAV transgenic plants. ABA treatment only negatively affected the germination rates of 35S:A-TsRAV transgenic seeds but not those of 35S:B-TsRAV transgenic seeds. All 35S:TsRAVs transgenic plants showed a similar degree of reduction in root growth compared with untreated seedlings in the presence of ABA. Furthermore, the cotyledon greening/expansion was more severely inhibited 35S:A-TsRAVs than in 35S:B-TsRAVs seedlings. Upon water deficiency, with a wider opening of stomata, 35S:A-TsRAVs plants experienced a faster transpirational water loss than wild type and 35S:B-TsRAVs lines. Taken together, our results suggest that two groups of TsRAVs perform distinct regulating roles during plant growth and abiotic defense including drought and salt, and A-TsRAVs are more likely than B-TsRAVs to act as negative regulators in the above-mentioned biological processes.

No MeSH data available.


Related in: MedlinePlus