Apical meristem exhaustion during determinate primary root growth in the moots koom 1 mutant of Arabidopsis thaliana

• Published in: Planta 2011-12, Vol.234 (6), p.1163-1177
• Main Authors: Hernández-Barrera, Alejandra, Ugartechea-Chirino, Yamel, Shishkova, Svetlana, Napsucialy-Mendivil, Selene, Soukup, Aleš, Reyes-Hernández, Blanca Jazmín, Lira-Ruan, Verónica, Dong, Gaofeng, Dubrovsky, Joseph G.
• Format: Article
• Language: English
• Subjects: Agriculture; Arabidopsis - drug effects; Arabidopsis - genetics; Arabidopsis - growth & development; Arabidopsis - physiology; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Auxins; Biological and medical sciences; Biomedical and Life Sciences; Cell cycle; Cell Division; Cell growth; Developmental stages; Ecology; Exhaustion; Forestry; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Plant - genetics; Germination; Homeodomain Proteins - genetics; Indoleacetic Acids - pharmacology; Life Sciences; Meristem - cytology; Meristem - drug effects; Meristem - genetics; Meristem - growth & development; Meristems; Mutants; Mutation; Original Article; Phenotype; Plant growth; Plant Growth Regulators - pharmacology; Plant roots; Plant Roots - cytology; Plant Roots - drug effects; Plant Roots - genetics; Plant Roots - growth & development; Plant Sciences; Plants; Promoter Regions, Genetic - genetics; Root growth; Seedlings; Seedlings - drug effects; Seedlings - genetics; Seedlings - growth & development; Signal Transduction - genetics; Stem Cell Niche; Stem cells; Transcription Factors - genetics; Transcription Factors - metabolism
• ISSN: 0032-0935; 1432-2048
• DOI: 10.1007/s00425-011-1470-4

An indeterminate developmental program allows plant organs to grow continuously by maintaining functional meristems over time. The molecular mechanisms involved in the maintenance of the root apical meristem are not completely understood. We have identified a new Arabidopsis thaliana mutant named moots koom 1 (mko1) that showed complete root apical meristem exhaustion of the primary root by 9 days post-germination. MKO1 is essential for maintenance of root cell proliferation. In the mutant, cell division is uncoupled from cell growth in the region corresponding to the root apical meristem. We established the sequence of cellular events that lead to meristem exhaustion in this mutant. Interestingly, the SCR and WOX5 promoters were active in the mko1 quiescent center at all developmental stages. However, during meristem exhaustion, the mutant root tip showed defects in starch accumulation in the columella and changes in auxin response pattern. Therefore, contrary to many described mutants, the determinate growth in mko1 seedlings does not appear to be a consequence of incorrect establishment or affected maintenance of the quiescent center but rather of cell proliferation defects both in stem cell niche and in the rest of the apical meristem. Our results support a model whereby the MKO1 gene plays an important role in the maintenance of the root apical meristem proliferative capacity and indeterminate root growth, which apparently acts independently of the SCR/SHR and WOX5 regulatory pathways.