Abstract
Plant organ growth is widely accepted to be determined by cell division and cell expansion, but, unlike that in animals, the contribution of cell elimination has rarely been recognized. We investigated this paradigm during Arabidopsis lateral root formation, when the lateral root primordia (LRP) must traverse three overlying cell layers within the parent root. A subset of LRP-overlying cells displayed the induction of marker genes for cell types undergoing developmental cell death, and their cell death was detected by electron, confocal, and light sheet microscopy techniques. LRP growth was delayed in cell-death-deficient mutants lacking the positive cell death regulator ORESARA1/ANAC092 (ORE1). LRP growth was restored in ore1-2 knockout plants by genetically inducing cell elimination in cells overlying the LRP or by physically killing LRP-overlying cells by ablation with optical tweezers. Our results support that, in addition to previously discovered mechanisms, cell elimination contributes to regulating lateral root emergence.
Highlights
In contrast to that in animals [1], cell elimination is generally considered not to play a role in regulating plant organ growth [2,3,4]
Cell death is not believed to occur during LR emergence (LRE) in Arabidopsis [25, 26], and the cell death reported in the lateral root (LR) primordium (LRP)-overlying cells of other species [12,13,14,15] has not been studied in relation to LRP growth, leaving open the question of whether cell death contributes to LRE
The present study investigates whether cell death occurs in the LRP-overlying cells during LRE in Arabidopsis, and if so, whether it contributes to LRP growth
Summary
In contrast to that in animals [1], cell elimination is generally considered not to play a role in regulating plant organ growth [2,3,4]. Cell death and the subsequent cell degradation are usually considered cell autonomous, as during the formation of water-conducting xylem tracheary elements (TEs) [8] or the elimination of lateral root cap cells that surround the root tip and regulate root growth [9]. The fact that different mechanisms have been co-opted to control developmental cell elimination supports that cell elimination plays several crucial roles during development, suggesting a more prominent role during plant organ growth than previously thought. Cell death is not believed to occur during LRE in Arabidopsis [25, 26], and the cell death reported in the LRP-overlying cells of other species [12,13,14,15] has not been studied in relation to LRP growth, leaving open the question of whether cell death contributes to LRE
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