毕氏海蓬子SbDREB基因的克隆与表达分析研究

以毕氏海蓬子的基因组为模板,通过PCR技术扩增到一个编码DREB蛋白AP2保守结构域的基因片段;根据该片段序列设计引物,以毕氏海蓬子经NaCl处理的植株肉质茎cDNA为模板,应用RACE技术获得该基因的cDNA全长,命名为SbDREB(GenBank登录号:JF894301)。SbDREB基因cDNA全长1206bp,包含一个编码284个氨基酸的完整开放阅读框。对氨基酸序列比对分析表明,该蛋白在靠近N端具有典型的AP2/EREBP保守结构域,且该结构域与一些高等植物DREB类转录因子的AP2区域具有高度同源性。进化树分析表明SbDREB属于DREB亚家族中的A-6亚族。实时荧光定量PCR结果显示:干旱、高盐和ABA能够诱导其表达,而低温则使其表达下调,表明该基因在毕氏海蓬子植株对干旱、盐和低温等非生物胁迫的应答中起作用。     

Involvement of a novel Arabidopsis phospholipase D, AtPLDdelta, in dehydration-inducible accumulation of phosphatidic acid in stress signalling

Phospholipid metabolism is involved in plant responses to drought and salinity stress. To investigate the role of phospholipase D (PLD) and its product phosphatidic acid (PtdOH) in stress signalling, we isolated a novel PLD cDNA, designated AtPLDdelta, by screening a cDNA library prepared from dehydrated Arabidopsis thaliana. The AtPLDdelta protein, of 868 amino acids, has a putative catalytic domain and a C2 domain that is involved in Ca2+/phospholipid binding. The AtPLDdelta mRNA accumulated in response to dehydration and high salt stress. Histochemical analysis showed that the AtPLDdelta gene is strongly expressed in the vascular tissues of cotyledons and leaves under dehydration stress conditions. Under normal growth conditions, AtPLDdelta was expressed in roots, leaves, stems and flowers but not in siliques. We showed that dehydration stimulates the accumulation of PtdOH. The accumulation of PtdOH in response to dehydration was significantly suppressed in AtPLDdelta antisense transgenic plants. These results suggest that AtPLDdelta may be involved in PtdOH accumulation in the dehydration stress response.     

Modulation of proliferation-specific and differentiation-specific markers in human keratinocytes by SMAD7

We examined the potential role of SMAD7 in human epidermal keratinocyte differentiation. Overexpression of SMAD7 inhibited the activity of the proliferation-specific promoters for the keratin 14 and cdc2 genes and reduced the expression of the mRNA for the proliferation-specific genes cdc2 and E2F1. The ability of SMAD7 to suppress cdc2 promoter activity was lost in transformed keratinocyte cell lines and was mediated by a domain(s) located between aa 195-395 of SMAD7. This domain lies outside the domain required to inhibit TGFbeta1 signaling, suggesting that this activity is mediated by a novel functional domain(s). Examination of AP1, NFkappaB, serum response element, Gli, wnt, and E2F responsive reporters indicated that SMAD7 significantly suppressed the E2F responsive reporter and modestly increased AP1 activity in proliferating keratinocytes. These data suggest that SMAD7 may have a role in TGFbeta-independent signaling events in proliferating/undifferentiated keratinocytes. The effects of SMAD7 in differentiated keratinocytes indicated a more traditional role for SMAD7 as an inhibitor of TGFbeta action. SMAD7 was unable to initiate the expression of differentiation markers but was able to superinduce/derepress differentiation-specific markers and genes in differentiated keratinocytes. This latter role is consistent with the ability of SMAD7 to inhibit TGFbeta-mediated suppression of keratinocyte differentiation and suggest that the opposing actions of SMAD7 and TGFbeta may serve to modulate squamous differentiation.     

AP2/EREBP 转录因子在植物发育和胁迫应答中的作用

AP2/EREBP (APETALA2/ethylene-res ponsive element binding proteins) 是一个起源古老的转录因子超家族, 它含有1个或2个由约60-70个氨基酸残基组成的非常保守的DNA结合域 (DNA-binding domain), 即AP2/ERF结构域。根据AP2/ERF结构域的数目, AP2/EREBP转录因子可以分为2个亚族: EREBP亚族(具有1个AP2/ERF结构域)和AP2亚族(具有2个AP2/ERF结构域)。AP2亚族转录因子有调控花、胚珠和种子发育的功能, 而EREBP亚族转录因子(包括DREB类和ERF类) 的主要功能是调节植物对激素(乙烯和ABA等)、病原和胁迫(低温、干旱及高盐)等的应答反应。本文讨论了AP2/EREBP转录因子在植物发育和胁迫应答中的研究进展。     

AP2/EREBP转录因子在植物发育和胁迫应答中的作用

AP2／EREBP（APETALA2/ethylene-responsive element binding proteins）是一个起源古老的转录因子超家族,它含有1个或2个由约60—70个氨基酸残基组成的非常保守的DNA结合域（DNA-binding domain）,即AP2／ERF结构域。根据AP2／ERF结构域的数目,AP2／EREBP转录因子可以分为2个亚族：EREBP亚族（具有1个AP2／ERF结构域）和AP2亚族（具有2个AP2／ERF结构域）。AP2亚族转录因子有调控花、胚珠和种子发育的功能,而EREBP亚族转录因子（包括DREB类和ERF类）的主要功能是调节植物对激素（乙烯和ABA等）、病原和胁迫（低温、干旱及高盐）等的应答反应。本文讨论了AP2／EREBP转录因子在植物发育和胁迫应答中的研究进展。