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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

ABA sensitivity of 35S:TsRAVs transgenic Arabidopsis plants.(A) Germination rates of 35S:TsRAVs transgenic Arabidopsis seeds on 1/2 MS media with 1 μM ABA. Each data bar represents the means ± SE of three replicates. More than 100 seeds were measured in each replicate. (B) Inhibitory effect of 1 μM ABA 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 30 μM ABA 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 30 μM ABA 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.g005: ABA sensitivity of 35S:TsRAVs transgenic Arabidopsis plants.(A) Germination rates of 35S:TsRAVs transgenic Arabidopsis seeds on 1/2 MS media with 1 μM ABA. Each data bar represents the means ± SE of three replicates. More than 100 seeds were measured in each replicate. (B) Inhibitory effect of 1 μM ABA 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 30 μM ABA 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 30 μM ABA 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: Abscisic acid (ABA) is a key phytohormone regulating many important plant growth and developmental events [39,43]. In the developing embryo, ABA accumulation regulates seed development, storage product accumulation, seed maturation, and seed dormancy [39,44]. The ABA content follows a rapid decline during imbibition process [45,46] and exogenous ABA inhibits seed germination and early seedling growth [38,39]. In the available literature, contrary results existed about the effect of RAV overexpression on the sensitivity of transgenic plant towards ABA inhibition during seed germination [4]. In this work, with the presence of 1 μM ABA, seed germination was significantly inhibited in WT and all transgenic lines (Fig 5A). With the germination rate at DAG 3 of WT seeds changed from 100% to 46%, the average germination rate of A-TsRAVs and B-TsRAVs transgenic seeds dropped from 64% to 10% and from 81% to 38%, respectively (Fig 5A). When the inhibitory effects of ABA were calculated against their normal germination rates, B-TsRAVs transgenic seeds were affected to a same extent as WT seeds, but to a much less extent than A-TsRAVs transgenic seeds (Fig 5B). Our work was consistent with the previous report that exogenous ABA inhibited the germination of both wild type and GhRAV1 overexpression transgenic seeds with a much greater degree of inhibition observed in the transgenic seeds than in wild type [18]. However, results contrary to our data also existed and a recent work revealed that RAV1-overexpressing lines showed strong ABA-insensitive phenotypes during seed germination and early seedling development, whereas RAV1-underexpressing lines were more sensitive to ABA than wild-type plants [15].


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)

ABA sensitivity of 35S:TsRAVs transgenic Arabidopsis plants.(A) Germination rates of 35S:TsRAVs transgenic Arabidopsis seeds on 1/2 MS media with 1 μM ABA. Each data bar represents the means ± SE of three replicates. More than 100 seeds were measured in each replicate. (B) Inhibitory effect of 1 μM ABA 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 30 μM ABA 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 30 μM ABA 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.g005: ABA sensitivity of 35S:TsRAVs transgenic Arabidopsis plants.(A) Germination rates of 35S:TsRAVs transgenic Arabidopsis seeds on 1/2 MS media with 1 μM ABA. Each data bar represents the means ± SE of three replicates. More than 100 seeds were measured in each replicate. (B) Inhibitory effect of 1 μM ABA 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 30 μM ABA 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 30 μM ABA 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: Abscisic acid (ABA) is a key phytohormone regulating many important plant growth and developmental events [39,43]. In the developing embryo, ABA accumulation regulates seed development, storage product accumulation, seed maturation, and seed dormancy [39,44]. The ABA content follows a rapid decline during imbibition process [45,46] and exogenous ABA inhibits seed germination and early seedling growth [38,39]. In the available literature, contrary results existed about the effect of RAV overexpression on the sensitivity of transgenic plant towards ABA inhibition during seed germination [4]. In this work, with the presence of 1 μM ABA, seed germination was significantly inhibited in WT and all transgenic lines (Fig 5A). With the germination rate at DAG 3 of WT seeds changed from 100% to 46%, the average germination rate of A-TsRAVs and B-TsRAVs transgenic seeds dropped from 64% to 10% and from 81% to 38%, respectively (Fig 5A). When the inhibitory effects of ABA were calculated against their normal germination rates, B-TsRAVs transgenic seeds were affected to a same extent as WT seeds, but to a much less extent than A-TsRAVs transgenic seeds (Fig 5B). Our work was consistent with the previous report that exogenous ABA inhibited the germination of both wild type and GhRAV1 overexpression transgenic seeds with a much greater degree of inhibition observed in the transgenic seeds than in wild type [18]. However, results contrary to our data also existed and a recent work revealed that RAV1-overexpressing lines showed strong ABA-insensitive phenotypes during seed germination and early seedling development, whereas RAV1-underexpressing lines were more sensitive to ABA than wild-type plants [15].

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