Recruitment of IC-WOX Genes in Root Evolution

Area of Science:

• Plant developmental biology
• Evolutionary genetics
• Molecular biology

Background:

• Root systems exhibit diverse evolutionary trajectories, including bifurcating roots in lycophytes and adventitious/lateral and primary roots in euphyllophytes.
• The genetic underpinnings of these distinct root developmental pathways remain incompletely understood.

Purpose of the Study:

• To investigate the role of intermediate-clade-WUSCHEL-RELATED HOMEOBOX (IC-WOX) genes in the evolution of plant root systems.
• To determine the specific functions of IC-WOX genes in different plant lineages, particularly ferns and seed plants.

Main Methods:

• Comparative gene expression analysis of IC-WOX genes in the fern Ceratopteris richardii and the seed plant Arabidopsis thaliana.
• Identification and characterization of IC-WOX subclades in seed plants.

Main Results:

• IC-WOX genes are expressed in founder cells of adventitious/lateral roots in the fern Ceratopteris richardii.
• In Arabidopsis thaliana, two IC-WOX subclades, AtWOX11/12 and AtWOX8/9, are involved in adventitious and primary root development, respectively.
• IC-WOX genes were likely recruited in the common ancestor of ferns and seed plants for adventitious/lateral root organogenesis.

Conclusions:

• IC-WOX genes played a pivotal role in the evolution of adventitious and lateral root development in euphyllophytes.
• Subsequent diversification of IC-WOX genes in seed plants led to the recruitment of one lineage for primary root development, while the other was retained for adventitious root formation.