Abstract
ABSTRACTCambium contains a stem cell population that produces xylem and phloem tissues in a radial direction during the secondary growth stage. The growth of many storage roots, including in the radish, Raphanus sativus L., also depends on cambium. Interestingly, we observed numerous adventitious roots (ARs) emerging from the cambia of cut surfaces when the bases of radish storage tap roots were removed. Previous studies in Arabidopsis showed that the WOX11/12 pathway regulates AR initiation and meristem establishment in an auxin-dependent manner. Here, we provide evidence indicating the evolutionary conservation of the WOX11/12 pathway during the AR development in radishes. Additionally, we found that expression of two cambium regulators, PXY and WOX4, is induced in the cambium regions that are connected to emerging ARs via vascularization. Both AR formation and genes associated with this were induced by exogenous auxin. Our research suggests that some key cambium regulators might be reprogrammed to aid in the AR development in concert with the WOX11/12 pathway.This article has an associated First Person interview with the first author of the paper.
Highlights
The vascular cambium is a meristem organized in radial files between the xylem and the phloem
Cambium cells are competent for adventitious root formation Tissues around cambia in cut stems of tomato and Eucalyptus have been shown to form adventitious roots (ARs)
In Arabidopsis the primary roots undergoing the secondary growth, cambium cells could lead to the formation of root founder cells for lateral roots (Baesso et al, 2018)
Summary
The vascular cambium is a meristem organized in radial files between the xylem and the phloem. The growth of radish storage root is driven by high cambium activity in the taproot (Fig. S1A,B). To see whether WOX11/12 pathway is associated with the AR formation in radish, we identified the orthologous genes of WOX11 and WOX12 in radish and analyzed their expression levels after inducing the regeneration of ARs from cut radish taproots for 2 weeks in hydroponic culture.
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