Departamento de Biologia Vegetal/Instituto de Biotecnologia Aplicada a Agropecuária (BIOAGRO), Universidade Federal de Viçosa, Viçosa, Minas Gerais, Brazil.
Universidade Estadual do Maranhão, São Luís, MA, Brazil.
Ann Bot. 2019 Jul 8;123(7):1191-1203. doi: 10.1093/aob/mcz025.
Juvenile-to-adult phase transition is marked by changes in leaf morphology, mostly due to the temporal development of the shoot apical meristem, a phenomenon known as heteroblasty. Sugars and microRNA-controlled modules are components of the heteroblastic process in Arabidopsis thaliana leaves. However, our understanding about their roles during phase-changing in other species, such as Passiflora edulis, remains limited. Unlike Arabidopsis, P. edulis (a semi-woody perennial climbing vine) undergoes remarkable changes in leaf morphology throughout juvenile-to-adult transition. Nonetheless, the underlying molecular mechanisms are unknown.
Here we evaluated the molecular mechanisms underlying the heteroblastic process by analysing the temporal expression of microRNAs and targets in leaves as well as the leaf metabolome during P. edulis development.
Metabolic profiling revealed a unique composition of metabolites associated with leaf heteroblasty. Increasing levels of glucose and α-trehalose were observed during juvenile-to-adult phase transition. Accumulation of microRNA156 (miR156) correlated with juvenile leaf traits, whilst miR172 transcript accumulation was associated with leaf adult traits. Importantly, glucose may mediate adult leaf characteristics during de novo shoot organogenesis by modulating miR156-targeted PeSPL9 expression levels at early stages of shoot development.
Altogether, our results suggest that specific sugars may act as co-regulators, along with two microRNAs, leading to leaf morphological modifications throughout juvenile-to-adult phase transition in P. edulis.
从幼年到成年的阶段转变以叶片形态的变化为标志，这主要是由于茎尖分生组织的时间发育，这一现象被称为异型性。糖和 microRNA 控制的模块是拟南芥叶片异型性过程的组成部分。然而，我们对它们在其他物种（如 Passiflora edulis）的阶段变化过程中的作用的了解仍然有限。与拟南芥不同，P. edulis（一种半木质多年生攀缘藤本植物）在幼年到成年的过渡过程中叶片形态发生显著变化。尽管如此，其潜在的分子机制尚不清楚。
在这里，我们通过分析 P. edulis 发育过程中叶片 microRNA 和靶基因的时间表达以及叶片代谢组学，评估了异型性过程的分子机制。
代谢组学分析揭示了与叶片异型性相关的独特代谢物组成。在从幼年到成年的阶段转变过程中，葡萄糖和α-海藻糖的水平逐渐增加。miR156 的积累与幼年叶片特征相关，而 miR172 转录物的积累与叶片成年特征相关。重要的是，葡萄糖可能通过调节新生成的茎器官发生过程中 miR156 靶向的 PeSPL9 表达水平来介导成年叶片特征，这一过程发生在茎发育的早期阶段。
总之，我们的研究结果表明，特定的糖可能与两种 microRNA 一起作为共调节剂，导致 P. edulis 从幼年到成年的阶段转变过程中叶片形态发生改变。
