The role of XAL1 in the root cell dynamics underpinning root growth

Morphogenesis depends on the modulation of cell proliferation and differentiation. The reverse genetics approach of García-Cruz et al. reveals that such modulation is dynamically adjusted in response to various signals via a complex transcriptional regulatory network that mediates between such signals and cell-cycle regulation and cell-fate decisions resulting in proliferation, growth or differentiation.

Overexpression of XAL1 is sufficient to promote root cell proliferation.
Overexpression of XAL1 is sufficient to promote root cell proliferation. (A, B) Meristem size (A) and meristematic cell number (B) are higher in the overexpression lines (XAL1-OE 5.2.5 and XAL1-OE 7.9.1) while XAL1-2 has both parameters diminished compared with WT roots at 5 dpg. Data correspond to mean ± s.e. Statistical significance (***P < 0·001, *P < 0·05) was obtained using the Kruskal–Wallis test (n = 30). (C) XAL1-overexpression increases cell divisions at the SCN. Confocal microscopy showing atypical divisions of the QC (arrowheads) and initial cells (labelled cells in the insets) in 50 % of the XAL1-OE 5.2.5 and 7.9.1 plants compared with WT roots. Seedlings of 3 dpg were stained with the pseudo-Schiff technique. n = 35 (WT), 20 (XAL1-OE 5.2.5) and 32 (XAL1-OE 7.9.1) plants. Scale bars = 10 μm.

XAL1 (AGL12) is a MADS-box transcription factor and an important component of such networks. This gene participates in root meristem proliferation by regulating cell-cycle components. Interestingly, overexpression of XAL1 is able to affect stem-cell divisions. The study shows that XAL1 is involved in the modulation of cell proliferation to differentiation, transitioning the entrance to the endoreplicative cell cycle during root development.

Root Biology Issue This paper is part of the Root Biology Special Issue.

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Karla V. García-Cruz, Berenice García-Ponce, Adriana Garay-Arroyo, María De La Paz Sanchez, Yamel Ugartechea-Chirino, Bénédicte Desvoyes, Mario A. Pacheco-Escobedo, Rosalinda Tapia-López, Ivan Ransom-Rodríguez, Crisanto Gutierrez, Elena R. Alvarez-Buylla, 2016, 'The MADS-box XAANTAL1 increases proliferation at the Arabidopsis root stem-cell niche and participates in transition to differentiation by regulating cell-cycle components', Annals of Botany, vol. 118, no. 4, pp. 787-796