Study of the Faux in the Verzy Forest (Fagus sylvatica variety tortuosa)

The objective of this project is help solve the mystery of the twisted beech phenotype, a mutant dwarf tree - Fagus sylvatica variety tortuosa – so far reported in several forests in France, Germany, Sweden and Denmark (see https://en.wikipedia.org/wiki/Faux_de_Verzy). The most famous stand is located in Verzy (25km south of Reims, France) where hundreds of Faux (their given name from the old French "fagus") characterized by their tortuous trunks and branches pending to the ground, have been preserved by the national forest office. More precisely, we aim at discovering the molecular bases of the mutation by comparing (i) the genomes of wild types (straight trees) and dwarf mutants, and (ii) genomic features (transcriptome, methylomes, mobilomes, small RNA populations, genomes) of six genotypes displaying both the mutant and wild type phenotypes. We hypothesized that the reversion of the mutation, resulting in a straight branch standing up from the typical igloo shape of the mutant, is caused by a somatic mutation in or near the mutated locus.

本项目旨在破解扭曲山毛榉表型（phenotype）的谜题——该突变矮化欧洲山毛榉扭曲变种（Fagus sylvatica variety tortuosa）目前已在法国、德国、瑞典及丹麦的多处森林中被报道（详见https://en.wikipedia.org/wiki/Faux_de_Verzy）。其中最著名的林分坐落于法国兰斯以南25公里的韦尔齐地区：当地数百株以古法语"fagus"（意为山毛榉）命名为"Faux"的树木，其树干与枝条扭曲盘旋、垂至地面，已由国家森林管理部门加以保护。具体而言，本研究旨在通过两组对比分析揭示该突变的分子基础：其一，对比野生型（直立正常植株）与矮化突变体的基因组（genome）；其二，分析6份同时表现出突变型与野生型表型的基因型的组学特征，涵盖转录组（transcriptome）、甲基化组（methylomes）、移动元件组（mobilomes）、小RNA群体（small RNA populations）及基因组。我们提出如下假说：突变逆转现象——即从典型"冰屋"形态的突变体上长出直立枝条——是由突变位点内部或其邻近区域发生的体细胞突变（somatic mutation）所引发的。