Brassinosteroid signaling and auxin transport are required to establish the periodic pattern of Arabidopsis shoot vascular bundles

Abstract

The plant vascular system provides transport and support capabilities that are essential for plant growth and development, yet the mechanisms directing the arrangement of vascular bundles within the shoot inflorescence stem remain unknown. We used computational and experimental biology to evaluate the role of auxin and brassinosteroid hormones in vascular patterning in Arabidopsis. We show that periodic auxin maxima controlled by polar transport and not overall auxin levels underlie vascular bundle spacing, whereas brassinosteroids modulate bundle number by promoting early procambial divisions. Overall, this study demonstrates that auxin polar transport coupled to brassinosteroid signaling is required to determine the radial pattern of vascular bundles in shoots.mathematical model ͉ pattern formation ͉ plant hormones ͉ procambium

The BRASSINOSTEROID INSENSITIVE1–LIKE3 Signalosome Complex Regulates Arabidopsis Root Development

“…Beyond the overall plant dwarfism, detailed phenotypic analysis has permitted the characterization of tissue-specific defects in plant vasculature Ibañes et al, 2009;Fàbregas et al, 2010), pollen development (Ye et al, 2010), root hair patterning (Kuppusamy et al, 2009), and QC activity (González-García et al, 2011). Signal amplification from the BRI1 receptor implies the transcriptional regulation of thousands of genes that, as direct targets of BES1 and BRZ1, may act in different cell types regulating different responses (Sun et al, 2010;Yu et al, 2011).…”

Theoretical approaches to understanding root vascular patterning: a consensus between recent models

“…In general, these models have all focused on the longitudinal flow of auxin; while there have been some models considering the radial flow of auxin in outer tissues (Swarup et al, 2005;Laskowski et al, 2008;Péret et al, 2013), these have not studied radial auxin flow through the vascular tissues. Other studies have considered radial pattering of the shoot using models formulated with a one-dimensional ring of cells (Ibañes et al, 2009;Fàbregas et al, 2015). There have also been models which consider the crosstalk between auxin and cytokinin, initially within the context of a single cell, but later in a one-dimensional line of cells (Muraro et al, 2011(Muraro et al, , 2013.…”

A systems biology approach to dissect the contribution of brassinosteroid and Auxin hormones to vascular patterning in the shoot ofArabidopsis thaliana

“…31 In Col-0 wild-type plants the differentiating xylem cells can be observed at approximately ∼100 µm below the shoot apex. 10 Longitudinal sections of the same plants show the connection between the stem vasculature and the vascular strands of secondary stems and floral organs (Fig. 1C).…”

“…17 Yet, it is not known whether the differentiating shoot vascular tissue is directing vascular patterning in more apical parts or whether the emergence of lateral organs and their vasculature, controlled by the SAM, is dictating shoot vascular patterning. The similarities between the mechanisms proposed for the role of auxin transport in phyllotaxy 22,32 and shoot vascular patterning 10 suggest to primarily analyse the latter scenario.…”

“…meristems and leaves during the generation of phyllotactic patterns. [19][20][21] To address how auxin polar transport controls shoot vascular patterning, we formulated a mathematical model for auxin transport dynamics, 10 which partially captured the complexity of previously proposed models. 22,23 A hypothesis of the model is that auxin is distributed in maxima, which in turn direct vascular bundle formation in shoots (Fig.…”