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Auxin regulation and differential distribution underlies many biological processes including meristem patterning, organogenesis and tropism. However, there remains the challenge of characterizing the enzymes involved in these processes. Auxin is the light-induced signal formed in leaves that triggers Ntann12 expression in roots mature cells. Without any stress, Ntann12 expression is observed only in light conditions. It is repressed by darkness and by auxin carrier inhibitors. Osmotic, salt and water stresses also repress Ntann12 expression. Therefore, abiotic stresses repress Ntann12 expression by reducing auxin availability or by inhibiting auxin transport. The analysis suggests that Ntann12 is implicated in auxin metabolism, possibly through an enzymatic function. Ntann12 is expressed in root mature cells where auxin turnover are naturally highest, and in leaves and root undifferentiated cells after exogenous application. This book therefore provides additional mechanisms by which IAA homeostasis is regulated. The analysis should help biologists and agronomists to better investigate plant tolerance to various stresses that are major limiting factors for plant growth and yield.

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Yves Oukouomi Lowé, Ph.D.: Studied Plant Biology at the ´Université Libre de Bruxelles´ (Belgium), Biosafety in Plant Biotechnology at the University of Ghent (Belgium) and Agriculture at the University of Dschang (Cameroon). Biologist, at the Canadian Food Inspection Agency, Ottawa (Canada).

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