Arabidopsis callus formation requires the activation of the lateral root initiation program

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• Kaoru Sugimoto, Caltech
• Thursday 07 July 2011, 14:00-15:00
• Tom ap Rees, Department of Plant Sciences.

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Unlike most animal cells, plant cells can easily regenerate new tissues from a wide variety of organs when properly cultured. The common elements that provide varied plant cells with their remarkable regeneration ability are still largely unknown. We characterized the initial process of Arabidopsis in vitro regeneration, where a pluripotent cell mass termed callus is induced. Using live imaging and whole-genome microarray analysis, we found that callus is not an undifferentiated tissue but a somewhat differentiated tissue similar to the tip part of a root meristem, even if it is derived from aerial organs such as petals, which clearly shows that callus formation is not a simple reprogramming process backwards to an undifferentiated state as widely believed. Furthermore, callus formation in roots, cotyledons and petals is blocked in mutant plants incapable of initial cell division of pericycle cells, a layer of tissue surrounding the vasculature whose division is an early step in formation of a lateral root. The expression pattern of pericycle markers that characterize lateral root initiation was observed in the callus-forming region of roots, cotyledons and petals. It thus appears that the ectopic activation of a lateral root development program in pericycle-like cells is a common mechanism in callus formation from multiple organs. We also tested various media containing different levels of plant hormones and confirmed that the conclusions drawn above apply to a wide range of medium conditions.

This talk is part of the What's on in Plant Sciences series.

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• Tom ap Rees, Department of Plant Sciences

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