植物WRKY转录因子及其参与的ABA信号转导

摘要：主要阐述了WRKY转录因子在非生物胁迫应答中的作用，以及其参与ABA信号转导方向的研究进展。

关键词：WRKY转录因子；非生物胁迫；ABA信号转导

中图分类号： S188 文献标识码： DOI编码：10.3969/j.issn.1006－6500.2012.06.005

由于植物的固着属性及自然界的环境变化，农林作物等植物时刻遭受着各种生物和非生物的胁迫，如病虫害、干旱、低温、高盐等，这些胁迫经常发生在植物生长发育的不同阶段，进而限制了植物的器官生长、组织发生和果实成熟等。为了适应多变的环境条件，植物自身存在着复杂的胁迫应答机制，从而实现在不同生长环境条件下正常生长发育。基于分子水平的胁迫应答信号转导在这一过程中起到了至关重要的作用，因此，阐明胁迫响应信号转导分子机制、识别相关调控因子是研究植物抗逆的关键。wrky转录因子作为一种多效性、瞬时性转录因子，能够参与多种生物或非生物胁迫反应以及植物发育等生理过程[1-2]，但其在脱落酸（ABA）响应的逆境胁迫信号转导中的作用研究较少。研究表明，ABA作为传统的植物激素之一，在植物逆境胁迫信号转导机制中扮演重要角色[3]。笔者主要从WRKY转录因子在非生物胁迫响应过程中的作用及其参与的aba信号转导方面阐述最近的研究进展。

1 植物WRKY转录因子

2 WRKY转录因子参与的ABA信号转导

2.1 ABAR受体介导的ABA信号转导

ABAR普遍存在于植物的绿色和非绿色组织，在植物细胞中发挥多重功能，不仅参与叶绿素合成，也是质体与细胞核之间信号转导的重要组分。研究表明，在种子发芽、生长和气孔运动过程中ABAR作为受体，能够特异性结合ABA，参与ABA信号转导，并正向调控信号转导的发生[22]。通过免疫荧光技术和酵母双杂交筛选证明，ABAR定位于叶绿体膜边缘，能够横跨叶绿体膜，并且其N末端和C末端在基质一侧，C末端能够结合ABA或与一组拟南芥WRKY转录因子（AtWRKY18、AtWRKY40、AtWRKY60）相互作用[6, 26]。其中ABAR与AtWRKY40的相互作用表明，AtWRKY40作为主要的负调控因子，可抑制ABA响应基因如ABI5的表达。当外源ABA刺激拟南芥植株时，ABA诱导AtWRKY40从细胞核向细胞质移动，促进ABAR与AtWRKY40的相互作用，从而缓解ABA响应基因的表达抑制。除了AtWRKY18、AtWRKY40、AtWRKY60基因的突变体植株，在ABA诱导的情况下，全部表现ABA过敏感型。除ABAR外，利用ChIP技术发现，WRKY40还能够直接与许多ABA响应基因如ABI4、ABI5、ABF4、MYB2等的启动子结合，从而调控基因表达[6]。这些试验结果也将WRKY确定在其他已知ABA响应转录因子AP2/ERF基因DREB1A、MYB基因MYB2、bZIP基因ABI5等的上游。分析单双突变和过表达试验结果，在种子发芽及发育阶段，AtWRKY40负调控ABA响应，AtWRKY18和AtWRKY60正调控ABA响应，且AtWRKY18和AtWRKY40能够被ABA快速诱导，AtWRKY60则较慢。研究人员还发现，AtWRKY40和AtWRKY18能够识别AtWRKY60启动子，调节AtWRKY60表达，这也说明了WRKY转录因子参与ABA信号转导的复杂性[8]。

2.2 PYR/PYL/RCAR受体介导的ABA信号转导

3 　 展望

随着新兴技术的发展，植物逆境胁迫响应信号转导与基因调控领域的研究不断深入，一些信号受体及转录调控因子的识别与定位，为我们更好地理解植物复杂的信号转导机制提供了新的思路。WRKY转录因子作为ABA信号通路中的关键调控因子，其参与植物非生物胁迫响应的研究成果，将会在农业生产上发挥重要的作用。

参考文献：

[1] Rushton P J, Somssich I E, Ringler P, et al. WRKY transcription factors [J]. Trends in Plant Science, 2010, 15(5):247-258.

[2] Pandey S P, Somssich I E. The role of WRKY transcription factors in plant immunity [J]. Plant Physiology, 2009, 150(4):1648-1655.

[3] Zhang J, Jia W, Yang J, et al. Role of ABA in integrating plant responses to drought and salt stresses [J]. Field Crops Research, 2006, 97(1):111-119.

[4] Chen L, Song Y, Li S, et al. The role of WRKY transcription factors in plant abiotic stresses [J]. Biochimica et Biophysica Acta (BBA) - Gene Regulatory Mechanisms, 2012, 18，19(2):120-128.

[5] Zhang H, Jin J, Tang L, et al. Plant TFDB 2.0: Update and improvement of the comprehensive plant transcription factor database [J]. Nucleic Acids Research, 2011, 39(1):1114-1117.

[6] Shang Y, Yan L, Liu Z-Q, et al. The Mg-chelatase H subunit of arabidopsis antagonizes a group of WRKY transcription repressors to relieve ABA-responsive genes of inhibition [J]. The Plant Cell Online, 2010, 22(6):1909-1935.

[7] Rushton D L, Tripathi P, Rabara R C, et al. WRKY transcription factors: Key components in abscisic acid signalling [J]. Plant Biotechnology Journal, 2012, 10(1):2-11.

[8] Chen H, Lai Z, Shi J, et al. Roles of arabidopsis WRKY18, WRKY40 and WRKY60 transcription factors in plant responses to abscisic acid and abiotic stress [J]. BMC Plant Biology, 2010, 10(1):281.

[9] Jiang W, Yu D. Arabidopsis WRKY2 transcription factor mediates seed germination and postgermination arrest of development by abscisic acid [J]. BMC Plant Biology, 2009, 9(1):96.

[10] Zhou X, Jiang Y, Yu D. WRKY22 transcription factor mediates dark-induced leaf senescence in Arabidopsis [J]. Molecules and Cells, 2011, 31(4):303-313.

[11] Li S, Fu Q, Chen L, et al. Arabidopsis thaliana WRKY25, WRKY26, and WRKY33 coordinate induction of plant thermotolerance [J]. Planta, 2011, 233(6):1237-1252.

[12] Ren X, Chen Z, Liu Y, et al. ABO3, a WRKY transcription factor, mediates plant responses to abscisic acid and drought tolerance in Arabidopsis [J]. The Plant Journal, 2010, 63(3):417-429.

[13] Qiu Y, Yu D. Over-expression of the stress-induced OsWRKY45 enhances disease resistance and drought tolerance in Arabidopsis [J]. Environmental and Experimental Botany, 2009, 65(1):35-47.

[14] Zhou Q-Y, Tian A-G, Zou H-F, et al. Soybean WRKY-type transcription factor genes, GmWRKY13, GmWRKY21, and GmWRKY54, confer differential tolerance to abiotic stresses in transgenic Arabidopsis plants [J]. Plant Biotechnology Journal, 2008, 6(5):486-503.

[15] Wei W, Zhang Y, Han L, et al. A novel WRKY transcriptional factor from thlaspi caerulescens negatively regulates the osmotic stress tolerance of transgenic tobacco [J]. Plant Cell Reports, 2008, 27(4):795-803.

[16] Mangelsen E, Wanke D, Kilian J, et al. Significance of light, sugar, and amino acid supply for diurnal gene regulation in developing barley caryopses [J]. Plant physiology, 2010, 153(1):14-33.

[17] Skibbe M, Qu N, Galis I, et al. Induced plant defenses in the natural environment: Nicotiana attenuata WRKY3 and WRKY6 coordinate responses to herbivory [J]. The Plant Cell Online, 2008, 20(7):1984-2000.

[18] Cutler S R, Rodriguez P L, Finkelstein R R, et al. Abscisic acid: Emergence of a core signaling network [J]. Annual Review of Plant Biology, 2010, 61(1):651-679.

[19] Razem F A, El-Kereamy A, Abrams S R, et al. The RNA-binding protein FCA is an abscisic acid receptor [J]. Nature, 2006, 439(7074):290-294.

[20] Liu X, Yue Y, Li B, et al. A G Protein-coupled receptor is a plasma membrane receptor for the plant hormone abscisic acid [J]. Science, 2007, 315(5819):1712-1716.

[21] Pandey S, Nelson D C, Assmann S M. Two novel GPCR-type G proteins are abscisic acid receptors in Arabidopsis [J]. Cell, 2009, 136(1):136-148.

[22] Shen Y Y, Wang X F, Wu F Q, et al. The Mg-chelatase H subunit is an abscisic acid receptor [J]. Nature, 2006, 443(7113):823-826.

[23] Park S Y, Fung P, Nishimura N, et al. Abscisic acid inhibits type 2C protein phosphatases via the PYR/PYL family of START proteins [J]. Science, 2009, 324(5930):1068-1071.

[24] Ma Y, Szostkiewicz I, Korte A, et al. Regulators of PP2C phosphatase activity function as abscisic acid sensors [J]. Science, 2009, 324(5930):1064-1068.

[25] Antoni R, Rodriguez L, Gonzalez-Guzman M, et al. News on ABA transport, protein degradation, and ABFs/WRKYs in ABA signaling [J]. Current Opinion in Plant Biology, 2011, 14(5):547-553.

[26] Wu F-Q, Xin Q, Cao Z, et al. The Magnesium-chelatase H subunit binds abscisic acid and functions in abscisic acid signaling: New evidence in Arabidopsis[J]. Plant physiology, 2009, 150(4):1940-1954.

[27] Fujii H, Chinnusamy V, Rodrigues A, et al. In vitro reconstitution of an abscisic acid signalling pathway [J]. Nature, 2009, 462(7273):660-664.

[28] Finkelstein R R, Gampala S S L, Rock C D. Abscisic acid signaling in seeds and seedlings [J]. The Plant Cell Online, 2002, 14(1):15-45.