Wang Xiaoping, Liu Shanda, Tian Hainan, Wang Shucai, Chen Jin-Gui
Key Laboratory of Molecular Epigenetics of Ministry of Education and Institute of Genetics and Cytology, Northeast Normal University , Changchun, China ; Biosciences Division, Oak Ridge National Laboratory , Oak Ridge, TN, USA.
Key Laboratory of Molecular Epigenetics of Ministry of Education and Institute of Genetics and Cytology, Northeast Normal University , Changchun, China.
Front Plant Sci. 2015 Nov 26;6:1064. doi: 10.3389/fpls.2015.01064. eCollection 2015.
Ethylene regulates many aspects of plant growth and development including seed germination, leaf senescence, and fruit ripening, and of plant responses to environmental stimuli including both biotic and abiotic stresses. Ethylene response factors (ERFs) are plant-specific transcription factors and are a subfamily of the AP2 (APETALA2)/ERF transcription factor family. The function of many members in this large gene family remains largely unknown. ERF96, a member of the Group IX ERF family transcription factors, has recently been shown to be a transcriptional activator that is involved in plant defense response in Arabidopsis. Here we provide evidence that ERF96 is a positive regulator of abscisic acid (ABA) responses. Bioinformatics analysis indicated that there are a total four small ERFs in Arabidopsis including ERF95, ERF96, ERF97, and ERF98, and that ERF96 forms a cluster with ERF95 and ERF97. By using quantitative RT-PCR, we found that ERF96 is expressed in all tissues and organs examined except roots, with relatively high expression in flowers and seeds. Results from the protoplast transfection assay indicated that the EDLL motif-containing C-terminal domain is responsible for ERF96's transcriptional activity. Although loss-of-function mutant of ERF96 was morphologically similar to wild type plants, transgenic plants overexpressing ERF96 had smaller rosette size and were delayed in flowering time. In ABA sensitivity assays, we found that ERF96 overexpression plants were hypersensitive to ABA in terms of ABA inhibition of seed germination, early seedling development and root elongation. Consistent with these observations, elevated transcript levels of some ABA-responsive genes including RD29A, ABI5, ABF3, ABF4, P5CS, and COR15A were observed in the transgenic plants in the presence of ABA. However, in the absence of ABA treatment, the transcript levels of these ABA-responsive genes remained largely unchanged. Our experiments also showed that water loss in ERF96 overexpression plants was slower than that in Col wild type plants. Stomatal closure assays indicated that ERF96 overexpression plants had reduced stomatal aperture in the presence of ABA. Taken together, our results suggest that ERF96 positively regulates ABA responses in Arabidopsis.
乙烯调节植物生长发育的许多方面，包括种子萌发、叶片衰老和果实成熟，以及植物对环境刺激（包括生物和非生物胁迫）的反应。乙烯反应因子（ERFs）是植物特有的转录因子，是AP2（APETALA2）/ERF转录因子家族的一个亚家族。这个大基因家族中许多成员的功能仍 largely未知。ERF96是第IX组ERF家族转录因子的成员，最近已被证明是一种参与拟南芥植物防御反应的转录激活因子。在这里，我们提供证据表明ERF96是脱落酸（ABA）反应的正调节因子。生物信息学分析表明，拟南芥共有四个小ERFs，包括ERF95、ERF96、ERF97和ERF98，并且ERF96与ERF95和ERF97形成一个簇。通过定量RT-PCR，我们发现ERF96在除根以外的所有检测组织和器官中均有表达，在花和种子中表达相对较高。原生质体转染试验结果表明，含EDLL基序的C末端结构域负责ERF96的转录活性。虽然ERF96功能缺失突变体在形态上与野生型植物相似，但过表达ERF96的转基因植物莲座叶尺寸较小，开花时间延迟。在ABA敏感性试验中，我们发现过表达ERF96的植物在ABA抑制种子萌发、早期幼苗发育和根伸长方面对ABA超敏感。与这些观察结果一致，在ABA存在的情况下，转基因植物中一些ABA反应基因（包括RD29A、ABI5、ABF3、ABF4、P5CS和COR15A）的转录水平升高。然而，在没有ABA处理的情况下，这些ABA反应基因的转录水平基本保持不变。我们的实验还表明，过表达ERF96的植物水分流失比Col野生型植物慢。气孔关闭试验表明，过表达ERF96的植物在ABA存在下气孔孔径减小。综上所述，我们的结果表明ERF96在拟南芥中正向调节ABA反应。
