In many dicot plants lateral roots arise from a dedicated cell file of the main root called pericycle. Initiation of lateral roots requires the phytohormone auxin that first triggers critical asymmetric cell divisions in the pericycle then acts as an instructive signal for lateral root growth and development.
While recent works have provided a large body of information concerning the role of auxin signaling and identified elements of the signaling pathway, our knowledge of the mechanism acting downstream of the auxin signal is still limited. In particular, we have just begun to understand the mechanism controlling the first critical formative pericycle divisions.
Plant growth depends on a root system that anchors plant in the soil and functions as an entry site for water and essential nutrients. Development of the root system is a post-embryonic process during which a highly branched network of lateral roots forms.
We have been studying lateral root initiation in the model plant Arabidopsis thaliana and identified a novel molecular mechanism that appears to regulate asymmetric pericycle cell divisions. Main components of this mechanism are the RETINOBLASTOMA-RELATED PROTEIN1 (RBR1) and the ATP-dependent chromatin remodeler PICKLE (PKL) that associates with RBR1. The RBR1-PKL complex negatively regulates expression of certain LDB genes whose activity is required for asymmetric pericycle cell division and lateral root initiation.
We are using biochemical, genetic and cell biology methods to elaborate on this repressor function and better understand the molecular mechanism which directs the RBR1-PKL complex to target loci, to dissect the subunit structure of the holocomplex and to elucidate how auxin signaling dissociate the complex. In ChIP-seq experiments we address the question whether the RBR1-PKL complex plays roles in other plant developmental processes.
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