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Accueil du site → Doctorat → Allemagne → 2006 → Mechanisms of salt tolerance : sodium, chloride and potassium homeostasis in two rice lines with different tolerance to salinity stress

Universität Bielefeld (2006)

Mechanisms of salt tolerance : sodium, chloride and potassium homeostasis in two rice lines with different tolerance to salinity stress

Diédhiou, Calliste Jérémie

Titre : Mechanisms of salt tolerance : sodium, chloride and potassium homeostasis in two rice lines with different tolerance to salinity stress

Mechanismen der Salztoleranz : Natrium-, Chlorid- und Kaliumhomöostase in zwei Reislinien mit unterschiedlicher Toleranz gegen Salzstress

Auteur : Diédhiou, Calliste Jérémie

Université de soutenance : Universität Bielefeld

Grade : Dr. rer. nat 2006

Résumé partiel
Rice marks second among the agricultural crop plants in the world (FAO, 2004). This work aimed at identifying the molecular mechanisms implicated in tolerance to salt. Salinity is a major environmental threat for agricultural production that affects ionic and osmotic as well as nutritional relation of plants. Ion channels are key players in maintaining ion homeostasis also under salinity. Cl- content was very low in control conditions but under 150 mM NaCl, Cl- was abundantly accumulated in leaves of the salt sensitive rice line IR29, whereas the salt tolerant line Pokkali excluded it from the leaves. Transcript of OsCLC1 i.e. voltage-dependent Cl- channels was found in both lines in roots and leaves under normal growth conditions and was repressed in IR29 and induced transiently in Pokkali upon salt treatment. Simultaneous, transcript amounts of the Na+/H+ antiporter OsNHX1 and the vacuolar H+-ATPase subunit OsVHA-B decreased in IR29, whereas Pokkali showed transient increase of OsVHA-B. Subsequent analysis of the water channel aquaporin OsPIP2 ;1 and the cell-specificity of OsCLC1 transcript distribution by in situ PCR showed coordinated regulation of OsCLC1, OsVHA-B, OsNHX1 and OsPIP2 ;1 on the one hand and suggest that OsCLC1 functions in osmotic adjustment at high salinity on the second hand. Transcript of the K+ transporter OsHAK7 that belongs to the HAK/KT/KUP family were also analysed in relation to K+ homeostasis. K+ content was high in plant tissues under normal conditions, however salt stress decreased root levels and strongly increased its accumulation in leaf cells in both IR29 and Pokkali. OsHAK7 showed high transcript abundance only during the first 6 h of the salt treatment in leaves, whereas in roots the induction was maintained up to 48 h in both lines. Tissue and cell-specificity distribution of OsHAK7 transcript by in situ PCR revealed expression in plant tissues under normal conditions. Strong signals in the mesophyll of both rice lines were detected in leaves, whereas expression in the vasculature cells was specific to Pokkali. In response to salt stress, transcript amounts were reduced in the mesophyll and were detectable in phloem and xylem parenchyma cells of both lines.

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