Regulatory Networks in the Development of Root System in Woody Plants: A Comparative Analysis of the Roles of Pericycle and Vascular Cambium - ISRR 2018 10th Symposium for the International Society of Root Research

author.DisplayName ^1,2 author.DisplayName ³ author.DisplayName ⁴ author.DisplayName ⁵

¹Dipartimento di Biotecnologie e Scienze della Vita, Università degli Studi dell'Insubria, Italy
²Università degli Studi dell'Insubria, Dipartimento di Biotecnologie e Scienze della Vita, Italy
³Department of Plant Biology, University of California, USA
⁴Department of Biosciences, University of Exeter, UK
⁵Dipartimento di Bioscienze e Territorio, Università del Molise, Italy

The production of a new lateral root from parental root primary tissues has been investigated extensively and the most important regulatory mechanisms are now well known. A first regulatory mechanism is based on the synthesis of small peptides which interact ectopically with membrane receptors to elicit a modulation of transcription factor target genes. A second mechanism involve a complex crosstalk between plant hormones. It is known that lateral roots are formed even in parental root portions characterize by the presence of secondary tissues, but there is not yet agreement about the putative tissue source providing the cells competent to become founder cells of a new root primordium. We produced anatomical evidence suggesting the vascular cambium as a candidate for such a role, but the regulatory mechanisms that may control such an event remain to be investigated.

We suggest models of possible regulatory mechanisms for inducing specific root vascular cambium stem cells to abandon their activity in the production of xylem and phloem elements and start the construction of a new lateral root primordium. Considering the vascular cambium ontogenic nature the models suggested are the result of a comparative review of mechanisms known to control the activity of stem cells in the root apex meristem, procambium, and vascular cambium. Stem cell of the root meristems can inherit various competences to play different roles and their fate could be decided in response to crosstalk between endogenous and exogenous signals.

We have found a high degree of relatedness among the regulatory mechanisms controlling the various root meristems. This fact suggests that competence to form new lateral roots can be inherited by some stem cells of the vascular cambium through lineage. This kind of competence could be represented by a sensitivity of specific stem cells to factors as those presented in our models.