Local brassinosteroid biosynthesis enables optimal root growth

Abstract

Brassinosteroid hormones are indispensable for root growth and they control both cell division and cell elongation through the establishment of an increasing signaling gradient along the longitudinal root axis. Because of their limited mobility, the importance of brassinosteroid distribution for achieving the signaling maximum is largely overlooked. Expression pattern analysis of all known brassinosteroid biosynthetic enzymes revealed that not all cells in the Arabidopsis thaliana root possess full biosynthetic machinery and completion of biosynthesis relies on cell-to-cell movement of the hormone precursors. We demonstrate that brassinosteroid biosynthesis is largely restricted to the root elongation zone where it overlaps with brassinosteroid signaling maxima. Moreover, optimal root growth requires hormone concentrations, low in the meristem and high in the root elongation zone attributable to an increased biosynthesis. Our finding that spatiotemporal regulation of hormone synthesis results in a local hormone accumulation provides a paradigm for hormone-driven organ growth in the absence of long-distance hormone transport in plants.

Brassinosteroid signaling regulates female germline specification in Arabidopsis

“…A recent study reported Article that BR biosynthetic enzymes exhibited different expression patterns in the Arabidopsis root and that BR intermediates need to be exchanged between neighboring cells for conversion to bioactive molecules. 33 It is possible that the completion of BR biosynthesis in ovules also relies on the cell-to-cell movement of BR precursors.…”

“…42 The same methods were used for generating KNU pro :BEH1, KNU pro :WRKY23 and BZR1 pro :WRKY23 constructs. Promoter-3xVENUS-N7 (for BRbiosynthetic genes and BEH2/3) were generated by amplifying 2 kbp upstream of the BR-biosynthetic genes, which have been shown to be fully functional, 33 and BEH2/3 genes sequences from wild-type genomic DNA using primers listed in Table S1. PCR fragments were cloned into the SPL4 pro :3xVENUS-N7 vector using BamHI and XbaI restriction sites.…”

Supraoptimal Brassinosteroid Levels Inhibit Root Growth by Reducing Root Meristem and Cell Elongation in Rice

“…Patterning of hormonal signals along root developmental axis is critical for optimal root growth and development. Local BR biosynthesis has been shown to peak in the elongation zone [ 33 ], coinciding with the optimal onset of cell elongation in the transition zone located between the meristem and elongation zone. As a result, exogenous BR or PPZ treatment may not promote optimal root elongation due to unbalanced activity in the meristem and elongation zone.…”

The Field Guide to 3D Printing in Microscopy

“…In the literature, whole microscope bodies have been printed, including the base (13,15), the body (13,15,16), holders for the filters (15,17), objectives (18), coverslips (14), pinholes (14,16) and heat sinks (18). Additionally, microscope chambers (19) and controller mounts (20) have also been implemented, allowing a high degree of customisation to researchers that adopt this technology. 3D printing is also used to print tools that allow for more complex microscopy solutions.…”