Cytoplasmic male sterility in tobacco: A plant genetic disease curable by gene therapy

Michel Hernould1, Agnès Bereterbide1, Isabelle Farbos2, Kristina Glimelius2 and Armand Mouras1
1UMR 0619 Biotechnologie et Physiologie Végétale, IBVM, INRA CR de Bordeaux, BP 81, F-33883 Villenave d'Ornon Cedex, France
2Department of Plant Biology, Uppsala Genetic Centre, Swedish University of Agricultural Sciences, Box 7080, S-750 07 Uppsala, Sweden

The alloplasmic tobacco line Nta(rep)S represents the material under investigation. This line exhibits a male-sterile phenotype and a defect in the development of male reproductive organs. The stamens are feminised and some of them are fused to the female reproductive organ indicating an impairment of the boundary between floral whorls # 3 and 4 corresponding to the stamens and carpel, respectively. Cytological analyses showed that floral abnormalities in the Nta(rep)S line are due to an impairment of the floral meristem. To verify that the cadastral-type abnormalities are linked to a misregulation of the NtSUP gene, the tobacco homolog of the SUPERMAN (SUP) gene from Arabidopsis, we performed complementation of this defect by ectopic expression of the Arabidopsis SUP gene. SUP over-expression in the Nta(rep)S line partially restores (i) the boundary between whorls # 3 and 4, (ii) stamen development, and (iii) male fertility. Furthermore, analysis of SUP over-expression in the fertile line allowed to bring more information on the functions of SUP from Arabidopsis. SUP negatively controls cell proliferation, but also cell expansion and differentiation. As the male sterility is maternally inherited in the Nta(rep)S line, the origin of NtSUP misregulation may be due to an epigenetic mechanism, such as a methylation process.


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