Mechanistic analysis of the transition from juvenility to maturity in perennial Arabis alpina and comparison with Brassica crop species

许多多年生植物表现出一个明确定义的幼年期，在此期间，即使暴露在诱导环境的提示下，它们也不会开花。我们开发了十字花科植物高山阿拉伯，作为草本植物的多年生模式植物。在这个物种中，幼年植物不会对春化做出反应，我们发现miRNA156的逐渐下降作为一个定时器，定义了幼年阶段的持续时间。在这里，我们建议加深我们对多年生植物幼体的了解。首先，我们将确定miRNA156的靶点，这些靶点是这一特征的基础。在高山拟青霉中，编码不同鳞状启动子结合样蛋白(SPL)转录因子的10个mRNAs是miRNA156的靶标。其中五个基因在开花诱导和与开花有关的拟南芥基因的同源基因周围表达。我们将产生阻止miRNA156与这5个mRNAs结合的突变，并测试哪些突变通过使年轻植物能够对春化做出反应来减少幼体阶段。其次，我们将利用现有的种群，通过杂交高山艾美耳球藻和一年生姐妹高山艾美耳球藻，没有可检测到的幼虫阶段，以遗传图谱和分离的基因座赋予这两个物种之间的幼体差异。第三，我们将扩大我们对在整个欧洲范围内收集的高山冰草的开花反应的描述，以测试幼体的种内自然遗传变异。第四，我们将追踪甘蓝属一年生和多年生物种之间的杂交，并探索这些物种中是否存在等位基因变异，这些基因座在Arabis中被确定为控制幼虫阶段的基因。这些实验建立在我们在优先方案中的早期工作的基础上，以阐明一年生和多年生植物之间的主要开花特征，并将结果推广到农作物。

Many perennial plants exhibit a clearly defined juvenile phase during which they will not flower even if exposed to inductive environmental cues. We developed Arabis alpina, a member of the Brassicaceae, as a herbaceaous perennial model. In this species juvenile plants do not flower in response to vernalization, and we found that the progressive decline of miRNA156 acts as a timer defining the duration of the juvenile phase. Here we propose to deepen our knowledge of juvenility in perennials. First we will identify targets of miRNA156 that underlie this trait. In A. alpina 10 mRNAs encoding different SQUAMOSA PROMOTER BINDING LIKE PROTEIN (SPL) transcription factors are targets of miRNA156. Five of these are expressed around floral induction and orthologues of A. thaliana genes implicated in flowering. We will generate mutations that prevent miRNA156 binding to each of these 5 mRNAs and test which of the mutations reduce the juvenile phase by enabling younger plants to respond to vernalization. Secondly, we will exploit existing populations made by crossing A. alpina and A. montbretiana, an annual sister of A. alpina with no detectable juvenile phase, to genetically map and isolate loci that confer the difference in juvenility between the two species. Thirdly, we will extend our characterization of the flowering responses of A. alpina accessions collected across its European range to test for intra-species natural-genetic variation for juvenility. Fourthly, we will pursue hybrid crosses carried out between annual and perennial species in the Brassica genus and explore whether allelic variation exists in these species at loci identified in Arabis as controlling the juvenile phase. These experiments build on our earlier work in the priority programme to elucidate a major flowering trait differing between annuals and perennials and to extend the results to crops.