Determinate root development in the halted primary root1 mutant of Arabidopsis correlates with death of root initial cells and an enhanced auxin response
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The transit from indeterminate to determinate root developmental program compromises growth and causes the differentiation of the meristem, but a direct link between this process with auxin signaling and/or viability of initial cells remains untested. Here, through the isolation and characterization of the halted primary root1 (hpr1) mutant of Arabidopsis, which develops primary and lateral roots with genetically stable determinate growth after germination, we show that the differentiation of the root meristem correlates with enhanced auxin responsiveness and is preceded by the death of provasculature initial cells in both primary and lateral roots. Supplementation of indole-3-acetic acid causes both a dose-dependent repression of primary root growth and an induction of DR5:uidA expression in wild-type seedlings, and these effects were exacerbated in hpr1 mutants. The damage of provasculature initial cells in the root of hpr1 mutants occurred at earlier times than the full differentiation of the meristem, and correlates with a reduced expression domain of CycB1:uidA and PRZ:uidA. Thus, HPR1 plays critical functions for stem cell maintenance, auxin homeostasis, cell division in the meristem, and indeterminate root growth.
KeywordsRoot stem cells Determinate root growth Cell viability Auxin Arabidopsis thaliana
We appreciate the generosity of Drs. Philip Benfey, Christian Luschnig, and Tom Guilfoyle for providing materials and the kind support of Drs. Bonnie Bartel and Bethany K. Zolman for recombination mapping of HPR1.
This study received funding from the Coordinación de la Investigación Científica UMSNH (México) via project 2.26 (JLB).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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