EXPANSIN A1-mediated radial swelling of pericycle cells positions anticlinal cell divisions during lateral root initiation ($) (PNAS)

Lateral root development helps plants explore the soil for mineral nutrients and water, and there are environmental and internal cues that precede the formation of lateral root primordia. In Arabidopsis thaliana, some of these internal cues include increased auxin concentrations around lateral root founder cells and their radial expansion. Ramakrishna et al. used an auxin-inducible lateral root proliferation system alongside non-degradable auxin-response repressors (IAA14 and IAA3) to identify genes involved in the early development of lateral root primordia. EXPA1, a cell wall remodeling protein, was identified through transcriptomic analysis, and subsequent microscopy demonstrated cell patterning irregularities during stage I in lateral root primordia of the expa1 mutant, as well as a delay in progression to stage II.  (Summary by Nathan Scinto-Madonich) Proc Natl. Acad. Sci. USA 10.1073/pnas.1820882116