Strategy of chalcone synthase antisense gene for a physiological approach in walnut rhizogenesis
Utilisation du gene antisens chalcone synthase pour une etude physiologique de la rhizogenese chez le noyer
Résumé
SUMMARY: In order to study the role of flavonoids in walnut rhizogenesis, genetic transformations were conducted on somatic embryos using mainly one vector containing the chalcone synthase antisense gene of petunia (ANTI-CHS) associated to GUS and NPTII genes. From this plant material, shoots were regenerated in tissue culture on which rooting tests and biochemical analyses were conducted. With regard to the controls, transformed shoots by ANTI-CHS were characterized by a relative low rooting capacity and a high accumulation of hydrojuglone glucoside and hydroxycinnamic acid. In addition, a significant reduction (20 to 60%) of myricitrin amount was found in leaves of the 3 transformed lines by ANTI-CHS. These results suggest that the antisense gene was partly active operating both on flavonoid accumulation in specific part of the explants and on the balance between the different phenolic metabolic pathways. New constructs with antisense sequences from 4 different chalcone synthase genes of walnut will be made to strengthen the biochemical and physiological effects of the first antisense gene used.
INTRODUCTION
Walnut trees produced valuable fruit and wood and are perfectly designated for agroforestry. Mass propagation of Juglans sp. is still an unsolved problem mainly due to an irregular adventitious root formation. Furthermore, flavonols are involved in rhizogenesis (CURIR et al., 1990) and it was shown that rooting in walnut trees was inhibited by myricitrin or promoted by myricetin. In addition, specific changes of endogenous content of quercitrin and myricitrin were found during the
RESUME: Différentes series de pousses in vitro ont été obtenues à partir d'embryons somatiques transformés (ou non) à l'aide principalement d'un vecteur composé du gène antisens chalcone synthase du pétunia (ANTI-CHS). Ces pousses transformées par ANTI-CHS ont été caractérisées par une faible aptitude à l'enracinement et par de fortes teneurs en hydrojuglone glucoside et en acide hydroxycinnamique. De plus, une diminution de 20 à 60% de myricitrinea été mis en évidence dans les feuilles des 3 lignées transformées par ANTI-CHS par comparaison à des pousses non transformées. De nouvelles constructions seront élaborées avec les séquences antisens de 4 gènes différents de la chalcone synthase du noyer. Elles permettront d'amplifier les effets biochimiques et physiologiques montrés au cours de ces premiers résultats.