Root Evolution

LRI-Thumbnail webStudying root development at the macro- and micro- evolutionary scale was facilitated the ongoing amelioration of phenotyping techniques, the extent of plant accessions databases and the arise of next-generation sequencing. Two main strategies have been initiated in the Root Development group to investigate micro-evolution of root architecture in Arabidopsis, and macro-evolution of genetic determinants of lateral root development in different species.

Micro-Evolution of Root Architecture in Arabidopsis: Genome-Wide Association Study (GWAS)

Plant sciences has been enriched recently with development of next generation sequencing, adaptation of statistical tools allowing for forward genetic screens in plants and further evolution of molecular tools available for Arabidopsis thaliana. Ultimately those advancements allow to direct plant research into in-depth analysis of pool of gene variability that is especially easily accessible and worldwide representative in Arabidopsis accessions. With data from high-throughput in vitro phenotyping of root architecture traits, genome-wide association studies are conducted. It is a tool used to correlate phenotyping data with SNPs information. As such, we are able to look more closely into what genes are underlying the conserved underground phenotypes in chosen A. thaliana accessions.

Example of different root systems architecture phenotypes observed among few of Arabidopsis thaliana accessions during in-vitro phenotyping experiments. Plants are 14 DAG old. 

We additionally evaluate the variability and stability of the traits in our in soil, rhizotron systems. This creates an opportunity to broaden the insight into certain underground phenotypes and even link it with shoot development and overall plant’s performance up to its flowering stage.

Images of plants grown in rhizotrons, in soil after 28 DAG.

 

Macro-Evolution of Lateral Root Development

Most of the knowledge about root development has been acquired from work in the model plant Arabidopsis. Although the regulatory mechanisms of lateral root initiation and root systems architecture are to a large extent unravelled, it is not known how universal this is or in what extent gene functions were conserved through the evolution. Therefore, in addition to the study of lateral root initiation in crops, we are studying lateral root initiation and root branching in several, evolutionary distinct, model plants. Used models include the early land plant and lycophyte Selaginella moellendorffii, the fern Ceratopteris richardii (C-fern) and angiosperms such as Medicago truncatula and Oryza sativa (rice).

Induced root branching in the lycophyte Selaginella moellendorffii.

Roots of Selaginella originated independently from roots of higher plants. They do not branch by lateral root formation, but by dichotomously splicing of the root tip. Despite of the independent evolution, some root development mechanisms from higher plants seems to be adopted by lycophytes too. Our research focusses on the commonly adopted regulators, as such revealing essential pathways in root development.

Sporophytes of C-fern treated with different compounds to screen for lateral root inducers.

In ferns, root develops differentially compared to angiosperms. For example, lateral root induction is not affected by auxins or auxin transport inhibitors (as applied in the Lateral Root Inducible System in Arabidopsis).

Induction of rice root primordia in a modified Lateral Root Inducible System.

People involved:

Boris Parizot - Coordinator and Co-promoter of the micro- and macro- evolution projects
Hans Motte - Co-promoter of the macro evolution project
Fang Tao - PhD student macro-evolution project
Agnieszka Deja - PhD student micro-evolution project

Selected publications:

Post-embryonic root organogenesis in cereals: branching out from model plants

Orman-Ligeza B, Parizot B, Gantet P, Beeckman T, Bennett MJ and Draye X (2013). Trends Plant Sci 18: 459-467.

Lateral Root Inducible System in Arabidopsis and Maize.

Crombez H, Roberts I, Vangheluwe N, Motte H, Jansen L, Beeckman T and Parizot B (2016). J Vis Exp 107, e53481 (doi:10.3791/53481).

Genomics of root development. 

Parizot B and Beeckman T (2012) Genomics of root development. In Roots Genomics and Soil Interactions, M. Crespi (Ed.), Blackwell Publishing Ltd., UK, pp. 3-28 [ISBN 978-1-118-44709-3].

Developmental Biology of Roots: One Common Pathway for All Angiosperms?

Grunewald W, Parizot B, Inzé D, Gheysen G and Beeckman T (2007) Int J Plant Dev Biol 1: 212–225.