Arabidopsis mutants deregulated in RCI2A expression reveal new signaling pathways in abiotic stress responses

To uncover new pathways involved in low-temperature signal transduction, we screened for mutants altered in cold-induced expression of RCI2A, an Arabidopsis gene that is not a member of the CBF/DREB1 regulon and is induced not only by low temperature but also by abscisic acid (ABA), dehydration (DH) and NaCl. This was accomplished by generating a line of Arabidopsis carrying a transgene consisting of the RCI2A promoter fused to the firefly luciferase coding sequence. A number of mutants showing low or high RCI2A expression in response to low temperature were identified. These mutants also displayed deregulated RCI2A expression in response to ABA, DH or NaCl. Interestingly, however, they were not altered in stress-induced expression of RD29A, a CBF/DREB1-target gene, suggesting that the mutations affect signaling intermediates of CBF/DREB1-independent regulatory pathways. Several mutants showed alterations in their tolerance to freezing, DH or salt stress, as well as in their ABA sensitivity, which indicates that the signaling intermediates defined by the corresponding mutations play an important role in Arabidopsis tolerance to abiotic stresses. Based on the mutants identified, we discuss the involvement of CBF/DREB1-independent pathways in modulating stress signaling.     

Differential response of cultivated rice to pathogen challenge and abiotic stresses with reference to cationic peroxidase

Seedlings of cultivated rice variety ADT43 was investigated after challenging with two different abiotic (drought and salinity) and biotic (sheath blight and bacterial leaf blight pathogens) stresses. Salinity and drought stress reduced the growth of seedlings, mainly the higher conditions (100 mM NaCl and 10?days of drought, respectively). Increased level of MDA content was observed in biotic and abiotic-stress treated seedlings. The highest H₂O₂ content was observed under salinity-stressed seedlings and lower level observed under biotic stress. Superoxide dismutase activity showed a gradual decrease in all stress conditions compared to control. Salinity stress resulted in highest activity of catalase compared to biotic stress. The peroxidase activity of the seedlings was found to be increased under salt and drought stress conditions and the activity decreased under biotic stress. Drought stress resulted in induced expression of POC1 gene whereas the biotic stress showed lower expression level. Suppression of the rice peroxidase would have been the mechanism of overcoming the intrinsic defence in rice by these pathogens.     

拟南芥基因芯片数据中非生物胁迫相关基因的挖掘

利用方差分析法从拟南芥芯片表达谱数据库挖掘非生物胁迫相关基因,并对这些基因进行GO注释分析,从而揭示非生物胁迫的生物学意义,发现非生物胁迫主要影响植物基因表达过程的转录调节和信号转导过程的磷酸化。同时对这些基因的上游启动子区域序列进行分析,挖掘非生物胁迫反应调控过程和适应过程的转录因子,发现植物非生物胁迫过程主要受bHLH—ZIP类和ZN—FINGER类C2H2型转录因子的调节。     

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。     

Glycerol-insensitive Arabidopsis mutants: gli1 seedlings lack glycerol kinase, accumulate glycerol and are more resistant to abiotic stress

The aim of this study was to investigate the process of glycerol catabolism in germinating Arabidopsis seed. A genetic screen was performed to isolate glycerol-insensitive (gli) mutant seedlings. Three separate mutant loci were identified (gli1, gli2 and gli3). Of these, only gli1 is unable to utilise glycerol. Following germination, gli1 seedlings transiently accumulate glycerol derived from the breakdown of storage oil and are more resistant to hyperosmotic stress, salt stress, oxidative stress, freezing and desiccation. Enzyme assays revealed that gli1 lacks glycerol kinase activity. GLI1 mapped to chromosome 1 near the putative glycerol kinase gene NHO1. Mutations in this gene were identified in three independent gli1 alleles. A cDNA encoding GLI1 was cloned and its function was proven by complementation of an Escherichia coli glycerol kinase (glpK) deletion strain. Quantitative RT-PCR analysis showed that GLI1 is expressed in all tissues, but is transiently upregulated during early post-germinative growth and leaf senescence. These data show that glycerol kinase is required for glycerol catabolism in Arabidopsis and that the accumulation of glycerol can enhance resistance to a variety of abiotic stresses associated with dehydration.     

Comprehensive expression analysis of rice phospholipase D gene family during abiotic stresses and development

Phospholipase D is one of the crucial enzymes involved in lipid mediated signaling, triggered during various developmental and physiological processes. Different members of PLD gene family have been known to be induced under different abiotic stresses and during developmental processes in various plant species. In this report, we are presenting a detailed microarray based expression analysis and expression profiles of entire set of PLD genes in rice genome, under three abiotic stresses (salt, cold and drought) and different developmental stages (3-vegetative stages and 11-reproductive stages). Seven and nine PLD genes were identified, which were expressed differentially under abiotic stresses and during reproductive developmental stages, respectively. PLD genes, which were expressed significantly under abiotic stresses exhibited an overlapping expression pattern and were also differentially expressed during developmental stages. Moreover, expression pattern for a set of stress induced genes was validated by real time PCR and it supported the microarray expression data. These findings emphasize the role of PLDs in abiotic stress signaling and development in rice. In addition, expression profiling for duplicated PLD genes revealed a functional divergence between the duplicated genes and signify the role of gene duplication in the evolution of this gene family in rice. This expressional study will provide an important platform in future for the functional characterization of PLDs in crop plants.     

植物抗坏血酸过氧化物酶的表达调控以及对非生物胁迫的耐受作用

抗坏血酸过氧化物酶(Ascorbate peroxidase, APX)属于I型血红素过氧化物酶, 它催化H2O2依赖的L-抗坏血酸氧化作用, 对抗坏血酸表现出高度的专一性。植物APX基因家族由4个亚家族组成, 分别为细胞质、叶绿体、线粒体和过氧化物酶体基因亚家族, 每个亚家族中又含有不同的APX同工酶。作为植物抗坏血酸-谷胱甘肽循环中的一个关键组分, APX在细胞H₂O₂代谢过程中起着至关重要的作用。研究表明植物APX是氧化还原信号系统中调节细胞水平H₂O₂非常重要的一种酶, APX同工酶的表达机制非常复杂, 细胞质APX受多种信号调节表达, 两种叶绿体APX通过选择性剪接进行组织特异性调节。通过调控产生的APX可调节细胞中的氧化还原信号, 进而提高植物对非生物胁迫的耐受性。文章综述了植物APX的催化机制、表达调控机理以及响应植物非生物逆境胁迫的重要作用。     

Cytokinin action in response to abiotic and biotic stresses in plants

The phytohormone cytokinin was originally discovered as a regulator of cell division. Later, it was described to be involved in regulating numerous processes in plant growth and development including meristem activity, tissue patterning, and organ size. More recently, diverse functions for cytokinin in the response to abiotic and biotic stresses have been reported. Cytokinin is required for the defence against high light stress and to protect plants from a novel type of abiotic stress caused by an altered photoperiod. Additionally, cytokinin has a role in the response to temperature, drought, osmotic, salt, and nutrient stress. Similarly, the full response to certain plant pathogens and herbivores requires a functional cytokinin signalling pathway. Conversely, different types of stress impact cytokinin homeostasis. The diverse functions of cytokinin in responses to stress and crosstalk with other hormones are described. Its emerging roles as a priming agent and as a regulator of growth‐defence trade‐offs are discussed.     

荷花 PIN 基因家族的鉴定及非生物胁迫表达分析

【目的】探究荷花中NnPIN家族成员的特征及在非生物胁迫响应中的作用,为荷花抗逆新品种的选育提供新的基因资源。【方法】采用生物信息学方法对荷花NnPIN家族进行全基因组鉴定,并通过qRT-PCR技术分析了其在低温(4℃)、水淹及外源3 mmol/L脱落酸(ABA)处理下的表达模式。【结果】(1)荷花基因组中共鉴定出12个具跨膜结构域的NnPIN基因,分别命名为NnPIN1～12,且分布在6条染色体上,并主要定位于质膜和内质网;(2)系统进化分析表明,NnPIN蛋白可根据中央亲水环的长度分为经典型和非经典型2种类型,且同一类型具相似结构;经典型具完整的motif 1～12,而非经典型则缺失中央亲水环部分(motif 6,8,9,12);(3)NnPIN基因在启动子区域具有大量光响应、非生物胁迫和激素响应元件,并特异性地具有厌氧、脱落酸(ABA)、低温等响应元件;(4)NnPIN基因(除NnPIN8外)均正向响应外源ABA和低温胁迫,而NnPIN6和NnPIN7正向响应水淹胁迫,NnPIN1、NnPIN2、NnPIN3、NnPIN4、NnPIN5、NnPIN8、NnPIN9和NnPIN12...     

Glutathione,photosynthesis and the redox regulation of stress-responsive gene expression

The ubiquitous antioxidant thiol tripeptide glutathione is present in millimolar concentrations in plant tissues and is regarded as one of the major determinants of cellular redox homeostasis. Recent research has highlighted a regulatory role for glutathione in influencing the expression of many genes important in plants' responses to both abiotic and biotic stress. Therefore, it becomes important to consider how glutathione levels and its redox state are influenced by environmental factors, how glutathione is integrated into primary metabolism and precisely how it can influence the functioning of signal transduction pathways by modulating cellular redox state. This review draws on a number of recent important observations and papers to present a unified view of how the responsiveness of glutathione to changes in photosynthesis may be one means of linking changes in nuclear gene expression to changes in the plant's external environment.