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Arabidopsis WRKY2 transcription factor mediates seed germination and postgermination arrest of development by abscisic acid.

Jiang W, Yu D - BMC Plant Biol. (2009)

Bottom Line: Analysis of WRKY2 expression level in ABA-insensitive and ABA-deficient mutants abi5-1, abi3-1, aba2-3 and aba3-1 further indicated that ABA-induced WRKY2 accumulation during germination and postgermination early growth requires ABI5, ABI3, ABA2 and ABA3.ABA hypersensitivity of the wrky2 mutants during seed germination and postgermination early seedling establishment is attributable to elevated mRNA levels of ABI5, ABI3 and ABI5-induced Em1 and Em6 in the mutants.ABI5, ABI3, ABA2 and ABA3 are important regulators of the transcripts of WRKY2 by ABA treatment.

View Article: PubMed Central - HTML - PubMed

Affiliation: Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Kunming, Yunnan 650223, PR China. jwb2001108@163.com

ABSTRACT

Background: Plant WRKY DNA-binding transcription factors are key regulators in certain developmental programs. A number of studies have suggested that WRKY genes may mediate seed germination and postgermination growth. However, it is unclear whether WRKY genes mediate ABA-dependent seed germination and postgermination growth arrest.

Results: To determine directly the role of Arabidopsis WRKY2 transcription factor during ABA-dependent seed germination and postgermination growth arrest, we isolated T-DNA insertion mutants. Two independent T-DNA insertion mutants for WRKY2 were hypersensitive to ABA responses only during seed germination and postgermination early growth. wrky2 mutants displayed delayed or decreased expression of ABI5 and ABI3, but increased or prolonged expression of Em1 and Em6. wrky2 mutants and wild type showed similar levels of expression for miR159 and its target genes MYB33 and MYB101. Analysis of WRKY2 expression level in ABA-insensitive and ABA-deficient mutants abi5-1, abi3-1, aba2-3 and aba3-1 further indicated that ABA-induced WRKY2 accumulation during germination and postgermination early growth requires ABI5, ABI3, ABA2 and ABA3.

Conclusion: ABA hypersensitivity of the wrky2 mutants during seed germination and postgermination early seedling establishment is attributable to elevated mRNA levels of ABI5, ABI3 and ABI5-induced Em1 and Em6 in the mutants. WRKY2-mediated ABA responses are independent of miR159 and its target genes MYB33 and MYB101. ABI5, ABI3, ABA2 and ABA3 are important regulators of the transcripts of WRKY2 by ABA treatment. Our results suggest that WRKY2 transcription factor mediates seed germination and postgermination developmental arrest by ABA.

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wrky2 mutants are hypersensitive to ABA responses in a short development window. (A) Seeds were germinated on MS medium 1 d after stratification, all were transferred to MS medium with 5 μM ABA. Photographs were taken 6 d after transfer. (B) Seeds were germinated on MS medium and 2 d after stratification, all were transferred to MS medium with 5 μM ABA. Photographs were taken 5 d after transfer. (C) Seeds were germinated on MS medium and 3 d after stratification, all were transferred to MS medium with 5 μM ABA. Photographs were taken 4 d after transfer.
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Figure 5: wrky2 mutants are hypersensitive to ABA responses in a short development window. (A) Seeds were germinated on MS medium 1 d after stratification, all were transferred to MS medium with 5 μM ABA. Photographs were taken 6 d after transfer. (B) Seeds were germinated on MS medium and 2 d after stratification, all were transferred to MS medium with 5 μM ABA. Photographs were taken 5 d after transfer. (C) Seeds were germinated on MS medium and 3 d after stratification, all were transferred to MS medium with 5 μM ABA. Photographs were taken 4 d after transfer.

Mentions: The transcription factors ABI3 and ABI5 are known to be important regulators of ABA-dependent growth arrest during germination [14,15]. ABI3 and ABI5 are reactivated by ABA during a short development window. Given the ABA hypersensitivity of wrky2 mutants, we studied the effect of ABA on the early development of wrky2 mutants. Application of 5 μM ABA [5] within 48 h post-stratification maintained the germinated embryos of wrky2 mutants in an arrested state for several days, but did not prevent germination, whereas a significant percentage of wild-type germinated embryos escaped growth arrest and turned green (Figure 5A and 5B). ABA applied outside the 48-h time frame failed to arrest growth and prevent greening (Figure 5C). If the seeds were transferred to ABA-containing media immediately or one day after stratification, we observed that the wrky2 mutants were more sensitive to ABA responses than the wild type. However, if the seeds were transferred to ABA-containing media 2 days post-stratification, there was no significant difference between the wild type and wrky2 mutants. These results indicated that wrky2 mutants were hypersensitive to ABA responses for a short development window.


Arabidopsis WRKY2 transcription factor mediates seed germination and postgermination arrest of development by abscisic acid.

Jiang W, Yu D - BMC Plant Biol. (2009)

wrky2 mutants are hypersensitive to ABA responses in a short development window. (A) Seeds were germinated on MS medium 1 d after stratification, all were transferred to MS medium with 5 μM ABA. Photographs were taken 6 d after transfer. (B) Seeds were germinated on MS medium and 2 d after stratification, all were transferred to MS medium with 5 μM ABA. Photographs were taken 5 d after transfer. (C) Seeds were germinated on MS medium and 3 d after stratification, all were transferred to MS medium with 5 μM ABA. Photographs were taken 4 d after transfer.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2719644&req=5

Figure 5: wrky2 mutants are hypersensitive to ABA responses in a short development window. (A) Seeds were germinated on MS medium 1 d after stratification, all were transferred to MS medium with 5 μM ABA. Photographs were taken 6 d after transfer. (B) Seeds were germinated on MS medium and 2 d after stratification, all were transferred to MS medium with 5 μM ABA. Photographs were taken 5 d after transfer. (C) Seeds were germinated on MS medium and 3 d after stratification, all were transferred to MS medium with 5 μM ABA. Photographs were taken 4 d after transfer.
Mentions: The transcription factors ABI3 and ABI5 are known to be important regulators of ABA-dependent growth arrest during germination [14,15]. ABI3 and ABI5 are reactivated by ABA during a short development window. Given the ABA hypersensitivity of wrky2 mutants, we studied the effect of ABA on the early development of wrky2 mutants. Application of 5 μM ABA [5] within 48 h post-stratification maintained the germinated embryos of wrky2 mutants in an arrested state for several days, but did not prevent germination, whereas a significant percentage of wild-type germinated embryos escaped growth arrest and turned green (Figure 5A and 5B). ABA applied outside the 48-h time frame failed to arrest growth and prevent greening (Figure 5C). If the seeds were transferred to ABA-containing media immediately or one day after stratification, we observed that the wrky2 mutants were more sensitive to ABA responses than the wild type. However, if the seeds were transferred to ABA-containing media 2 days post-stratification, there was no significant difference between the wild type and wrky2 mutants. These results indicated that wrky2 mutants were hypersensitive to ABA responses for a short development window.

Bottom Line: Analysis of WRKY2 expression level in ABA-insensitive and ABA-deficient mutants abi5-1, abi3-1, aba2-3 and aba3-1 further indicated that ABA-induced WRKY2 accumulation during germination and postgermination early growth requires ABI5, ABI3, ABA2 and ABA3.ABA hypersensitivity of the wrky2 mutants during seed germination and postgermination early seedling establishment is attributable to elevated mRNA levels of ABI5, ABI3 and ABI5-induced Em1 and Em6 in the mutants.ABI5, ABI3, ABA2 and ABA3 are important regulators of the transcripts of WRKY2 by ABA treatment.

View Article: PubMed Central - HTML - PubMed

Affiliation: Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Kunming, Yunnan 650223, PR China. jwb2001108@163.com

ABSTRACT

Background: Plant WRKY DNA-binding transcription factors are key regulators in certain developmental programs. A number of studies have suggested that WRKY genes may mediate seed germination and postgermination growth. However, it is unclear whether WRKY genes mediate ABA-dependent seed germination and postgermination growth arrest.

Results: To determine directly the role of Arabidopsis WRKY2 transcription factor during ABA-dependent seed germination and postgermination growth arrest, we isolated T-DNA insertion mutants. Two independent T-DNA insertion mutants for WRKY2 were hypersensitive to ABA responses only during seed germination and postgermination early growth. wrky2 mutants displayed delayed or decreased expression of ABI5 and ABI3, but increased or prolonged expression of Em1 and Em6. wrky2 mutants and wild type showed similar levels of expression for miR159 and its target genes MYB33 and MYB101. Analysis of WRKY2 expression level in ABA-insensitive and ABA-deficient mutants abi5-1, abi3-1, aba2-3 and aba3-1 further indicated that ABA-induced WRKY2 accumulation during germination and postgermination early growth requires ABI5, ABI3, ABA2 and ABA3.

Conclusion: ABA hypersensitivity of the wrky2 mutants during seed germination and postgermination early seedling establishment is attributable to elevated mRNA levels of ABI5, ABI3 and ABI5-induced Em1 and Em6 in the mutants. WRKY2-mediated ABA responses are independent of miR159 and its target genes MYB33 and MYB101. ABI5, ABI3, ABA2 and ABA3 are important regulators of the transcripts of WRKY2 by ABA treatment. Our results suggest that WRKY2 transcription factor mediates seed germination and postgermination developmental arrest by ABA.

Show MeSH
Related in: MedlinePlus