Auxin modulates the transition from the mitotic cycle to the endocycle in Arabidopsis

Abstract

SUMMARYAmplification of genomic DNA by endoreduplication often marks the initiation of cell differentiation in animals and plants. The transition from mitotic cycles to endocycles should be developmentally programmed but how this process is regulated remains largely unknown. We show that the plant growth regulator auxin modulates the switch from mitotic cycles to endocycles in Arabidopsis; high levels of TIR1-AUX/IAA-ARF-dependent auxin signalling are required to repress endocycles, thus maintaining cells in mitotic cycles. By contrast, lower levels of TIR1-AUX/IAA-ARF-dependent auxin signalling trigger an exit from mitotic cycles and an entry into endocycles. Our data further demonstrate that this auxin-mediated modulation of the mitotic-to-endocycle switch is tightly coupled with the developmental transition from cell proliferation to cell differentiation in the Arabidopsis root meristem. The transient reduction of auxin signalling by an auxin antagonist PEO-IAA rapidly downregulates the expression of several core cell cycle genes, and we show that overexpressing one of the genes, CYCLIN A2;3 (CYCA2;3), partially suppresses an early initiation of cell differentiation induced by PEO-IAA. Taken together, these results suggest that auxin-mediated mitotic-to-endocycle transition might be part of the developmental programmes that balance cell proliferation and cell differentiation in the Arabidopsis root meristem.

Jasmonate Controls Leaf Growth by Repressing Cell Proliferation and the Onset of Endoreduplication while Maintaining a Potential Stand-By Mode

“…Finally, quantification of nuclear surface area visualized by histone 2B-yellow fluorescent protein (H2B-YFP; Campilho et al, 2006) fusion proteins using confocal microscopy was performed according to Ishida et al (2010) in 6-d-old wild-type roots untreated or continuously treated with MeJA. Following exposure to MeJA, the average size of the nuclei in Arabidopsis root cells of the meristematic and elongation zones was reduced (Fig.…”

“…Hence, we have undertaken a novel full-genome Ishida et al (2010). A, Average nuclear area, defined as total pixel intensities of H2B-YFP signals per individual nucleus, was quantified within cells of the same epidermal layers in the meristem and the elongation zone of untreated and MeJA-treated roots.…”

Identification of transcription factors linked to cell cycle regulation inArabidopsis

“…Phytohormones such as auxin control organ cell proliferation via altering cell numbers as well as determination of organ size. [49][50][51] Auxin is required for the G1/S phase transition in cell cycle and initiation of DNA replication. Auxin together with cytokinin activates cell cycle regulatory genes which promote cell division, expansion and differentiation in root and shoot apical meristems 52,42 ;(Bhalerao and Bennett, 2003).…”

Cytokinins promote onset of endoreplication by controlling cell cycle machinery

“…22 It was s h o w n t h a t , in the transition zone, cytokinins activate ARR1 and ARR12 transcription factors that directly induce the expression of SHY2/IAA3, a member of the Aux/IAA family of auxin signaling repressors. This inhibits auxin signaling and reduces the expression of PIN-FORMED (PIN ) genes, thus suppressing cell division.…”