Jiang Wenbo, Yu Diqiu
Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Kunming, Yunnan 650223, PR China.
BMC Plant Biol. 2009 Jul 22;9:96. doi: 10.1186/1471-2229-9-96.
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.
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.
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.
植物WRKY DNA结合转录因子是特定发育程序中的关键调节因子。多项研究表明，WRKY基因可能介导种子萌发和萌发后生长。然而，尚不清楚WRKY基因是否介导ABA依赖的种子萌发和萌发后生长停滞。
为了直接确定拟南芥WRKY2转录因子在ABA依赖的种子萌发和萌发后生长停滞过程中的作用，我们分离了T-DNA插入突变体。两个独立的WRKY2的T-DNA插入突变体仅在种子萌发和萌发后早期生长期间对ABA反应超敏感。wrky2突变体中ABI5和ABI3的表达延迟或降低，但Em1和Em6的表达增加或延长。wrky2突变体和野生型显示出miR159及其靶基因MYB33和MYB101的相似表达水平。对ABA不敏感和ABA缺陷突变体abi5-1、abi3-1、aba2-3和aba3-1中WRKY2表达水平的分析进一步表明，在萌发和萌发后早期生长期间ABA诱导的WRKY2积累需要ABI5、ABI3、ABA2和ABA3。
wrky2突变体在种子萌发和萌发后早期幼苗建立过程中对ABA的超敏感性归因于突变体中ABI5、ABI3以及ABI5诱导的Em1和Em6的mRNA水平升高。WRKY2介导的ABA反应独立于miR159及其靶基因MYB33和MYB101。ABI5、ABI3、ABA2和ABA3是ABA处理WRKY2转录本的重要调节因子。我们的结果表明，WRKY2转录因子介导ABA依赖的种子萌发和萌发后发育停滞。
