The Role of Ribosome Biogenesis in Arabidopsis thaliana Root Development andEpidermal Patterning.

[摘要] The establishment of distinct patterns of gene expression is essential to the differentiation of specialized cell types during the development of multicellular organisms.To investigate the regulatory networks involved in this cell fate specification, one can turn to the Arabidopsis root epidermis, where a position-dependent pattern of hair and non-hair cells serves as a pertinent and accessible model.Recent studies have implicated ribosomal protein and ribosome assembly factors in regulation of gene expression during development, however, the connection between ribosome biogenesis and root cell-type patterning has previously never been investigated.To that end, this thesis research explores the connection and function of a highly conserved ribosome biogenesis factor with respect to the development and epidermal patterning of the Arabidopsis root epidermis.The Arabidopsis DIM1A gene was identified in a genetic screen for genes required for position-dependent expression of non-hair fate regulator GLABRA2.Our analysis has revealed that functional DIM1A is required for generation of distinct gene expression patterns in developing root-hair and non-hair cells.In addition to defects in root epidermal patterning, the dim1A mutant displays reduced root meristem cell division rate and deficient leaf size, shape, vascular patterning and trichome branching.Furthermore, DIM1A promoter activity and gene product are enriched in rapidly dividing plant tissues, supporting a role for DIM1A in Arabidopsis development and cell differentiation. The Dim1/KsgA family of dimethylases are a highly conserved enzymes involved in post-transcriptional modification of ribosomal RNA (rRNA) and pre-rRNA processing.While the two small subunit RNA base modifications they catalyze are present in almost every known organism, the functional significance of these modifications is currently unknown.My experimental evidence indicates that the dim1A mutant lacks the two 18S rRNA modifications without affecting pre-rRNA processing.In conclusion, I propose that DIM1A and the post-transcriptional rRNA modification it catalyzes are important for generating well-defined patterns of gene expression necessary for establishment of the two distinct cell fates in the Arabidopsis root epidermis.

[发布机构] University of Michigan

[效力级别] Arabidopsis Root Epidermal Cell Patterning

[关键词] Cell Fate Specification;Arabidopsis Root Epidermal Cell Patterning;Ribosome Biogenesis;DIM1A;Arabidopsis Root Development;Molecular;Cellular and Developmental Biology;Science;Molecular, Cellular, and Developmental Biology