水稻OsWRKY转录因子对非生物胁迫响应的重叠表达特性分析

WRKY转录因子是植物一类比较大的基因家族,在水稻中已鉴定出102个成员。研究表明WRKY转录因子在植物生长发育、抗病耐逆等方面都具有重要的作用。本研究利用基因芯片数据结合实时定量分析,对水稻Os WRKY转录因子基因在不同的非生物逆境下的表达进行了分析,发现至少有33个Os WRKY基因同时对任何两种非生物胁迫因子做出响应,且所选20个基因中,13个基因可被ABA所诱导。OsWRKY基因这种重叠表达的特性,预示着这些基因在非生物逆境中具有功能多效性,对于培育抗逆境水稻品种具有重要的理论与实践意义。     

受非生物胁迫和稻瘟病胁迫双重诱导的OsWRKY转录因子基因表达特征分析

OsWRKY 转录因子在水稻非生物胁迫和抗病反应中具有相当重要的调节作用。为阐明其调节作用提供依据,研究了疑似功能广泛的 OsWRKY 转录因子表达谱,采用五个 OsWRKY 转录因子基因,即 Os-WRKY7、OsWRKY11、OsWRKY30、OsWRKY70和 OsWRKY89,利用 real-time PCR 研究各种非生物胁迫和稻瘟菌胁迫诱导表达特征,以及各种激素对 OsWRKY 表达量的影响。所采用的五个基因均受到稻瘟菌胁迫的诱导,而且各种非生物胁迫也能不同程度地诱导其表达。在各个激素处理下,有些被诱导或被抑制,也有未受影响。五个 OsWRKY 基因均有可能参与稻瘟病胁迫响应。其中 OsWRKY7和 OsWRKY70可能是在JA 和 SA 相互拮抗调控下参与,OsWRKY89可能是通过非本研究涉及的其他激素途径参与。在非生物胁迫方面,OsWRKY7可能通过 ABA 途径参与干旱、高盐和极端温度胁迫;OsWRKY11有可能参与高盐胁迫;OsWRKY30有可能参与高盐和高温胁迫;OsWRKY70可能参与高盐、干旱和极端温度胁迫;OsWRKY89可能参与高温胁迫,但并不是通过本研究所涉及的四种激素途径。     

Annotations and functional analyses of the rice WRKY gene superfamily reveal positive and negative regulators of abscisic acid signaling in aleurone cells

The WRKY proteins are a superfamily of regulators that control diverse developmental and physiological processes. This family was believed to be plant specific until the recent identification of WRKY genes in nonphotosynthetic eukaryotes. We have undertaken a comprehensive computational analysis of the rice (Oryza sativa) genomic sequences and predicted the structures of 81 OsWRKY genes, 48 of which are supported by full-length cDNA sequences. Eleven OsWRKY proteins contain two conserved WRKY domains, while the rest have only one. Phylogenetic analyses of the WRKY domain sequences provide support for the hypothesis that gene duplication of single- and two-domain WRKY genes, and loss of the WRKY domain, occurred in the evolutionary history of this gene family in rice. The phylogeny deduced from the WRKY domain peptide sequences is further supported by the position and phase of the intron in the regions encoding the WRKY domains. Analyses for chromosomal distributions reveal that 26% of the predicted OsWRKY genes are located on chromosome 1. Among the dozen genes tested, OsWRKY24, -51, -71, and -72 are induced by abscisic acid (ABA) in aleurone cells. Using a transient expression system, we have demonstrated that OsWRKY24 and -45 repress ABA induction of the HVA22 promoter-beta-glucuronidase construct, while OsWRKY72 and -77 synergistically interact with ABA to activate this reporter construct. This study provides a solid base for functional genomics studies of this important superfamily of regulatory genes in monocotyledonous plants and reveals a novel function for WRKY genes, i.e. mediating plant responses to ABA.     

The C-terminal region of OsWRKY30 is sufficient to confer enhanced resistance to pathogen and activate the expression of defense-related genes

WRKY proteins are known to play major roles in defense signaling. We identified a pathogen-inducible and SA-inducible OsWRKY30. Our cDNA clone encodes the C-terminal region (CTR) of OsWRKY30. CTR-OsWRKY30 includes the C-terminal WRKY domain and nuclear localization sequence. CTR-OsWRKY30 was sufficient to bind W-box sequences (TTGACC/T). Over-expression of the CTR-OsWRKY30 resulted in enhanced resistance to pathogens in Arabidopsis and rice. Defense-related genes were constitutively expressed in transgenic Arabidopsis and rice over-expressing CTR-OsWRKY30. Based on promoter transient assays, CTR-OsWRKY30 is sufficient to activate OsPR10a promoter as much as full length OsWRKY30. Taken together, CTR-OsWRKY30 positively regulates defense signaling, thereby resulting in enhanced resistance to pathogens.     

OsWRKY13 mediates rice disease resistance by regulating defense-related genes in salicylate- and jasmonate-dependent signaling

Although 109 WRKY genes have been identified in the rice genome, the functions of most are unknown. Here, we show that OsWRKY13 plays a pivotal role in rice disease resistance. Overexpression of OsWRKY13 can enhance rice resistance to bacterial blight and fungal blast, two of the most devastating diseases of rice worldwide, at both the seedling and adult stages, and shows no influence on the fertility. This overexpression was accompanied by the activation of salicylic acid (SA) synthesis-related genes and SA-responsive genes and the suppression of jasmonic acid (JA) synthesis-related genes and JA-responsive genes. OsWRKY13 bound to the promoters of its own and at least three other genes in SA- and JA-dependent signaling pathways. Its DNA-binding activity was influenced by pathogen infection. These results suggest that OsWRKY13, as an activator of the SA-dependent pathway and a suppressor of JA-dependent pathways, mediates rice resistance by directly or indirectly regulating the expression of a subset of genes acting both upstream and downstream of SA and JA. Furthermore, OsWRKY13 will provide a transgenic tool for engineering wider-spectrum and whole-growth-stage resistance rice in breeding programs.