Expression profiling of auxin-treated Arabidopsis roots: toward a molecular analysis of lateral root emergence.

Treating Arabidopsis roots with exogenous auxin results in dramatic changes in cellular processes including de novo induction of lateral roots which later emerge through the overlying cells. Microarray experiments reveal approximately 80 genes that are substantially up-regulated in the root over the first 12 h following auxin treatment. We hypothesize that the observed increase in expression of pectate lyase family genes leads to degradation of the pectin-rich middle lamellae, allowing cells in the parent root to separate cleanly. Differences in the degree of pectin methylation in lateral and parent roots may explain why lateral roots are not degraded themselves.