花序分生组织特性基因TFL1的系统发育及其功能分析

TFL1同源基因在维持植物营养生长和花序分生组织特性方面起着非常重要的作用,其功能的丧失常导致植物提早开花,花序的正常发育受到抑制,最终茎端形成顶花。至今已经有28种植物的TFL1基因被克隆到,其中包括拟南芥、金鱼草和番茄等模式植物。TFL1 蛋白的系统发育树基本符合物种的亲缘关系。作为花序分生组织特性基因的TFL1与花分生组织特性基因LFY 和AP1相互作用,抑制花序分生组织向花分生组织的转变。TFL1和LFY等基因可用来培育早花新品种,也可用于培育无果的新品种,减少悬铃木、杨、柳等果毛的污染。     

实时荧光PCR技术对小麦矮腥黑穗病菌的检测

通过对小麦矮腥黑穗病菌(TCK)及其近似种小麦网腥黑穗病菌(TCT)和小麦光腥黑穗病菌(TFL)的rDNA序列ETS区间测序比较分析,找出了TCK相对于TCT和TFL的特异性序列,并根据TCK的特异性序列设计了实时荧光PCR探针,利用实时荧光PCR技术成功实现了对TCK的检测。     

AGO1 controls arabidopsis inflorescence architecture possibly by regulating TFL1 expression

Background and Aims

The TERMINAL FLOWER 1 (TFL1) gene is pivotal in the control of inflorescence architecture in arabidopsis. Thus, tfl1 mutants flower early and have a very short inflorescence phase, while TFL1-overexpressing plants have extended vegetative and inflorescence phases, producing many coflorescences. TFL1 is expressed in the shoot meristems, never in the flowers. In the inflorescence apex, TFL1 keeps the floral genes LEAFY (LFY) and APETALA1 (AP1) restricted to the flower, while LFY and AP1 restrict TFL1 to the inflorescence meristem. In spite of the central role of TFL1 in inflorescence architecture, regulation of its expression is poorly understood. This study aims to expand the understanding of inflorescence development by identifying and studying novel TFL1 regulators.

Methods

Mutagenesis of an Arabidopsis thaliana line carrying a TFL1::GUS (β-glucuronidase) reporter construct was used to isolate a mutant with altered TFL1 expression. The mutated gene was identified by positional cloning. Expression of TFL1 and TFL1::GUS was analysed by real-time PCR and histochemical GUS detection. Double-mutant analysis was used to assess the contribution of TFL1 to the inflorescence mutant phenotype.

Key Results

A mutant with both an increased number of coflorescences and high and ectopic TFL1 expression was isolated. Cloning of the mutated gene showed that both phenotypes were caused by a mutation in the ARGONAUTE1 (AGO1) gene, which encodes a key component of the RNA silencing machinery. Analysis of another ago1 allele indicated that the proliferation of coflorescences and ectopic TFL1 expression phenotypes are not allele specific. The increased number of coflorescences is suppressed in ago1 tfl1 double mutants.

Conclusions

The results identify AGO1 as a repressor of TFL1 expression. Moreover, they reveal a novel role for AGO1 in inflorescence development, controlling the production of coflorescences. AGO1 seems to play this role through regulating TFL1 expression.     

Four TFL1/CEN-Like Genes on Distinct Linkage Groups Show Different Expression Patterns to Regulate Vegetative and Reproductive Development in Apple (Malusxdomestica Borkh.)

Recent molecular analyses in several plant species revealedthat TERMINAL FLOWER1 (TFL1) and CENTRORADIALIS (CEN) homologsare involved in regulating the flowering time and/or maintainingthe inflorescence meristem. In apple (Malusxdomestica Borkh.),four TFL1/CEN-like genes, MdTFL1, MdTFL1a, MdCENa and MdCENb,were found and mapped by a similar position on putatively homoeologouslinkage groups. Apple TFL1/CEN-like genes functioned equivalentlyto TFL1 when expressed constitutively in transgenic Arabidopsisplants, suggesting that they have a potential to complementthe TFL1 function. Because MdTFL1 and MdTFL1a were expressedin the vegetative tissues in both the adult and juvenile phases,they could function redundantly as a flowering repressor anda regulator of vegetative meristem identity. On the other hand,MdCENa was mainly expressed in fruit receptacles, cultured tissuesand roots, suggesting that it is involved in the developmentof proliferating tissues but not in the control of the transitionfrom the juvenile to the adult phase. In contrast, MdCENb wassilenced in most organs probably due to gene duplication bythe polyploid origin of apple. The expression patterns of MdTFL1and MdCENa in apple were also supported by the heterologousexpression of β-glucuronidase fused with their promoterregions in transgenic Arabidopsis. Our results suggest thatfunctional divergence of the roles in the regulation of vegetativemeristem identity may have occurred among four TFL1/CEN-likegenes during evolution in apple.