互花米草NAC转录因子家族的鉴定与表达分析

互花米草(Spartina alterniflora)作为一种海岸带盐生植物,高度耐盐胁迫,但因为缺少参考基因组,其耐盐的分子机制却尚未见报道。NAC家族蛋白是植物特有的转录因子,调控植物的生长发育和胁迫应答。为了鉴定互花米草NAC蛋白(SaNAC)并探究它们与互花米草生长发育及胁迫响应之间的关系,本研究以互花米草三代全长转录组数据为参考,通过与水稻(Oryza sativa)、拟南芥(Arabidopsis thaliana)和玉米(Zea mays)NAC蛋白序列进行比对,并结合保守功能域进一步筛选,最终找到62个SaNAC蛋白。从蛋白序列比对、进化、motif预测、同源性比较、亚细胞定位、组织表达以及非生物胁迫下的基因差异表达等方面分别对互花米草NAC家族成员进行分析,结果发现SaNAC蛋白均含有保守的NAM结构域,且在进化上与水稻NAC家族具有一定的相似性;SaNAC家族中的两个蛋白SaNAC9和SaNAC49在细胞核表达;另外,本研究还发现互花米草SaNAC基因表达具有高度组织和胁迫应答差异性。这些结果表明互花米草NAC转录因子家族不仅具有保守的功能域,而且在调控互花米草的生长发育和非生物胁迫响应过程中具有重要的作用。     

番茄NAC转录因子家族的鉴定及生物信息学分析

NAC转录因子家族是植物特有的一类转录因子,在植物的生长发育、器官建成及逆境胁迫和激素信号应答中均发挥重要作用。本研究在基因组范围内,利用生物信息学方法对番茄的NAC转录因子家族成员、分布及结构和功能等进行分析。预测结果显示番茄NAC家族包含102个蛋白质,分为12亚族,其中茄属特有的TNAC亚族中成员最多,具有25个,其他NAC转录因子与拟南芥NAc家族具有相似分类。保守基序分析,在番茄NAC结构域中包含7个保守的NAM基序,主要分布在序列的N端,表明这些基序的存在对NAC蛋白质功能的执行是必需的。理化性质和结构分析表明,番茄NAC蛋白质绝大多数是亲水蛋白质,主要以无规则卷曲构成,而α-螺旋、β-折叠和β-转角则散布于整个蛋白质中,在各亚族中没有规律。     

转录因子Atonal家族的研究进展

转录因子atonal因其具有一个碱性螺旋-环-螺旋（bHLH）结构而被归属于bHLH转录因子家族,在调节真核生物生长发育过程中起着重要作用.目前的实验研究已经证明它与视觉、听觉、嗅觉的形成有关,同时在不同时期还能够决定细胞的分化命运和抑制肿瘤的扩散.主要从模式生物果蝇和小鼠中的基因结构、组织分布、功能特征等方面研究概述,为进一步了解其他物种atonal转录因子的功能和作用机制奠定基础.     

Differential combinatorial interactions of <Emphasis Type="Italic">cis</Emphasis>-acting elements recognized by R2R3-MYB,BZIP, and BHLH factors control light-responsive and tissue-specific activation of phenylpropanoid biosynthesis genes

Chalcone synthase (CHS), chalcone flavanone isomerase (CFI), flavanone 3-hydroxylase (F3H) and flavonol synthase (FLS) catalyze successive steps in the biosynthetic pathway leading to the production of flavonols. We show that in Arabidopsis thaliana all four corresponding genes are coordinately expressed in response to light, and are spatially coexpressed in siliques, flowers and leaves. Light regulatory units (LRUs) sufficient for light responsiveness were identified in all four promoters. Each unit consists of two necessary elements, namely a MYB-recognition element (MRE) and an ACGT-containing element (ACE). C1 and Sn, a R2R3-MYB and a BHLH factor, respectively, known to control tissue specific anthocyanin biosynthesis in Z. mays, were together able to activate the AtCHS promoter. This activation of the CHS promoter required an intact MRE and a newly identified sequence designated R response element (RRE ^AtCHS) containing the BHLH factor consensus binding site CANNTG. The RRE was dispensable for light responsiveness, and the ACE was not necessary for activation by C1/Sn. These data suggest that a BHLH and a R2R3-MYB factor cooperate in directing tissue-specific production of flavonoids, while an ACE-binding factor, potentially a BZIP, and a R2R3-MYB factor work together in conferring light responsiveness.     

Identification of a novel cis-acting element conferring sulfur deficiency response in Arabidopsis roots

SULTR1;1 high-affinity sulfate transporter is highly regulated in the epidermis and cortex of Arabidopsis roots responding to sulfur deficiency (-S). We identified a novel cis-acting element involved in the -S-inducible expression of sulfur-responsive genes in Arabidopsis. The promoter region of SULTR1;1 was dissected for deletion and gain-of-function analysis using luciferase (LUC) reporter gene in transgenic Arabidopsis. The 16-bp sulfur-responsive element (SURE) from -2777 to -2762 of SULTR1;1 promoter was sufficient and necessary for the -S-responsive expression, which was reversed when supplied with cysteine and glutathione (GSH). The SURE sequence contained an auxin response factor (ARF) binding sequence (GAGACA). However, SURE was not responsive to naphthalene acetic acid, indicating its specific function in the sulfur response. The base substitution analysis indicated the significance of a 5-bp sequence (GAGAC) within the conserved ARF binding site as a core element for the -S response. Microarray analysis of early -S response in Arabidopsis roots indicated the presence of SURE core sequences in the promoter regions of -S-inducible genes on a full genome GeneChip array. It is suggested that SURE core sequences may commonly regulate the expression of a gene set required for adaptation to the -S environment.     

Identification of a critical control element directing expression of the muscle-specific transcription factor MRF4 in the mouse embryo

Skeletal muscle development in the vertebrate embryo critically depends on the myogenic regulatory factors (MRFs) including MRF4 and Myf5. Both genes exhibit distinct expression patterns during mouse embryogenesis, although they are genetically closely linked with multiple regulatory elements dispersed throughout the common gene locus. MRF4 has a biphasic expression profile, first in somites and later in foetal skeletal muscles. Here, we demonstrate by transgenic analysis that elements within a 7.5-kb promoter fragment of the MRF4 gene are sufficient to drive the embryonic wave of expression very similar to the endogenous gene in somites of mouse embryos. In contrast, a 3-kb fragment of the proximal promoter fails to support expression in the myotome, suggesting that essential cis-acting elements are located between -7.5 and -3 kb upstream of MRF4. Further analysis of this sequence delimits an essential region between -6.6 and -5.6 kb that together with the 3-kb promoter fragment directs transgene expression in the epaxial myotome of all somites during the appropriate developmental period. These data provide evidence that the partly overlapping expression patterns of Mrf4 and Myf5 in somites are controlled by distinct regulatory elements. We also show that 11.4 kb sequence upstream of MRF4, including the promoter and the somitic control region identified in this study, is not sufficient to elicit target specificity towards the strong Myf5 (-58/-48 kb) enhancer, suggesting that additional yet unidentified elements are necessary to convey promoter selectivity and protect the MRF4 gene from this enhancer.     

Disruption of a novel gene for a NAC-domain protein in rice confers resistance to Rice dwarf virus

Rice dwarf virus (RDV) is a serious viral pest that is transmitted to rice plants ( Oryza sativa L.) by leafhoppers and causes a dwarfism in infected plants. To identify host factors involved in the multiplication of RDV, we screened Tos17 insertion mutant lines of rice for mutants with reduced susceptibility to RDV. One mutant, designated rim1-1 , did not show typical disease symptoms upon infection with RDV. The accumulation of RDV capsid proteins was also drastically reduced in inoculated rim1-1 mutant plants. Co-segregation and complementation analyses revealed that the rim1-1 mutation had been caused by insertion of Tos17 in an intron of a novel NAC gene. The rim1-1 mutant remained susceptible to the two other viruses tested, one of which is also transmitted by leafhoppers, suggesting that the multiplication rather than transmission of RDV is specifically impaired in this mutant. We propose that RIM1 functions as a host factor that is required for multiplication of RDV in rice.     

NAC转录因子在植物抗病和抗非生物胁迫反应中的作用

NAC转录因子是植物特有的一类转录因子,其共同特点是在N端含有一段高度保守、由约150个氨基酸组成的NAC结构域,而C端为高度变异的转录调控区。研究表明,NAC转录因子不仅参与植物生长发育的调控,而且在植物抗逆反应中具有重要的调控作用。文章着重介绍NAC转录因子在植物抗逆反应中的作用及其调控机制,并简要讨论NAC转录因子生物学功能的研究方向。