Comparison of lignin deposition in three ectopic lignification mutants.

The Arabidopsis thaliana mutants de-etiolated3 (det3), pom-pom1 (pom1) and ectopic lignification1 (eli1) all deposit lignins in cells where these polymers would not normally be found. Comparison of these mutants provides an opportunity to determine if the shared mutant phenotype arose by perturbing a common regulatory mechanism in each of the mutants. The mutants were compared using a combination of genetics, histochemistry, chemical profiling, transcript profiling using both Northern blots and microarrays, and bioinformatics. The subset of cells that ectopically lignified was shared between all three mutants, but clear differences in cell wall chemistry were evident between the mutants. Northern blot analysis of lignin biosynthetic genes over diurnal and circadian cycles revealed that transcript abundance of several key genes was clearly altered in all three mutants. Microarray analysis suggests that changes in the expression of specific members of the R2R3-MYB and Dof transcription factor families may contribute to the ectopic lignification phenotypes. This comparative analysis provides a suite of hypotheses that can be tested to examine the control of lignin biosynthesis.