Fernández-Nohales P, Domenech M J, Martínez de Alba A E, Micol J L, Ponce M R, Madueño F
Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Científicas-Universidad Politécnica de Valencia, Valencia 46022, Spain.
Institut Jean-Pierre Bourgin, UMR 1318, INRA, Route de St-Cyr, 78000 Versailles, France.
Ann Bot. 2014 Nov;114(7):1471-81. doi: 10.1093/aob/mcu132. Epub 2014 Jul 2.
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.
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.
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.
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.
TERMINAL FLOWER 1（TFL1）基因在拟南芥花序结构的控制中起关键作用。因此，tfl1突变体开花早且花序期非常短，而过量表达TFL1的植株营养期和花序期延长，产生许多共花序。TFL1在茎尖分生组织中表达，在花中从不表达。在花序顶端，TFL1使花器官基因LEAFY（LFY）和APETALA1（AP1）局限于花中，而LFY和AP1将TFL1局限于花序分生组织。尽管TFL1在花序结构中起核心作用，但其表达调控却知之甚少。本研究旨在通过鉴定和研究新的TFL1调控因子来拓展对花序发育的认识。
利用携带TFL1::GUS（β-葡萄糖醛酸酶）报告基因构建体的拟南芥品系进行诱变，以分离出TFL1表达改变的突变体。通过定位克隆鉴定突变基因。通过实时PCR和组织化学GUS检测分析TFL1和TFL1::GUS的表达。利用双突变分析评估TFL1对花序突变体表型的贡献。
分离出一个共花序数量增加且TFL1表达量高且异位表达的突变体。突变基因的克隆表明，这两种表型均由ARGONAUTE1（AGO1）基因的突变引起，该基因编码RNA沉默机制的关键组分。对另一个ago1等位基因的分析表明，共花序增殖和异位TFL1表达表型并非等位基因特异性的。在ago1 tfl1双突变体中，共花序数量增加的现象受到抑制。
结果表明AGO1是TFL1表达的抑制因子。此外，还揭示了AGO1在花序发育中的新作用，即控制共花序的产生。AGO1似乎通过调节TFL1表达发挥这一作用。
