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Functional analysis of a cytoplasmic male sterility in Arabidopsis thaliana

Abstract : This work aims at better understand the events leading to pollen abortion in a recently discovered gametophytic cytoplasmic male sterility (CMS) in Arabidopsis thaliana. Although CMS have been widely used in hybrid seed production in many crops, the physiological mechanisms leading to pollen death by the mitochondrial sterilizing genes in the permissive (maintainer) nuclear backgrounds are poorly understood. Association genetics previously identified orf117Sha as a candidate mitochondrial CMS-associated gene.In a first part, I analyzed the expression of the orf117Sha gene in sterile plants and in fertile plants carrying nuclear genes restoring male fertility. I observed unusual features of its mRNA, but detected no difference at this level between sterile and restored plants. Oppositely, the ORF117SHA protein seems to be accumulated specifically in the sterile line, supporting its role in CMS. A phenocopy attempt by transgenesis suggested a possible link between a female and male gametophytic lethality and the ORF117SHA, even though few individuals could be analyzed.In a second part, I observed pollen development in sterile plants and fertile controls using different cytological approaches. My results show a progressive pollen death starting from the binucleate stage in the sterile. Prior to abortion, pollen mitochondria swell before rupture, and the development stops. I used confocal microscopy combined with genetically encoded sensors to explore specific physiological features in pollen and vegetative tissues of sterile plants. With ATeam, which allows the assessment of ATP content in the cytosol, I could challenge the generally accepted hypothesis of an ATP deficiency leading to pollen abortion in CMS. Indeed, the ATP production does not seem to be affected in the sterile line. With a mitochondria-addressed roGFP2-Grx1, I was able to assess the redox state of the glutathione pool in vegetative tissues and in the male gametophyte. I observed an overoxydation of the glutathione pool in mitochondria of the sterile line, in vegetative tissue investigated and in the pollen grain. This overoxydation seems to be linked to the CMS as it is annihilated by the presence of restorer genes.My results pave the way for further exploration of the links between the sterility protein, mitochondrial morphology changes, mitochondrial overoxydation, and pollen development arrest and death in the A. thaliana CMS.
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  • HAL Id : tel-01941706, version 1

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Noémie Dehaene. Functional analysis of a cytoplasmic male sterility in Arabidopsis thaliana. Vegetal Biology. Université Paris Saclay (COmUE), 2017. English. ⟨NNT : 2017SACLS418⟩. ⟨tel-01941706⟩

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