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Ethylene receptors modulate fruit development and ripening

Chen, Yi. Ethylene receptors modulate fruit development and ripening. PhD, Développement des Plantes, Institut National Polytechnique de Toulouse, 2019

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Abstract

Ethylene is synthesized and perceived by all plants, and it is one of the most important phytohormone controlling fruit ripening. Ethylene is perceived by endoplasmic reticulum (ER)- localized proteins, called Ethylene Receptors (ETRs), which regulate fruit development and ripening, however the mechanisms by which ETRs regulate fruit ripening are not fully explained. Firstly, to study if ETRs regulate the ripening of climacteric and non-climacteric fruits, we compared ETRs and related protein members of both classes of fruit and by re-analyzing RNAseq data, already published, we found that ETRs were peaking at the inception of ripening in both climacteric and non- climacteric fruits, but in these data, the ETRs showed an earlier ETR expression peak relative to sugar accumulation. In this review, we also compared the structure of the ethylene receptors and related proteins in both classes of fruit, establishing a basis for the annotation of genes related to ethylene perception. Finally, the results show that there was a higher number of ETR genes in climacteric fruits than in non-climacteric fruits. Secondly, in tomato which is a fleshy fruit ripening model, a seventh ETR has been reported recently, following the genome sequencing. Characterization of this SlETR7 was carried out. We showed that ethylene binds to the transmembrane part of SlETR7. Like other ETR expression patterns during fruit ripening, SlETR7 expression in pericarp also goes up when fruit ripens. The profiles of the seven ETR expression during fruit ripening can be divided in 2 groups: group 1, ETR3, ETR4, and ETR6 are expressed earlier at Breaker+2 days than group 2, SlETR1, SlETR2, SlETR5, and SlETR7 that are expressed at a later stage of ripening. We constructed Knock Out (KO) and OverExpressed (OE) tomato lines for SlETR7, and we observed some phenotype changes proving that SlETR7 is a functional ETR. While there was only a small phenotype change in KO plants and fruits: more ethylene production at Br and Br+2days compared to Wild Type (WT). The OE lines showed early flowering, shorter plants, and smaller fruit than WT. The analyzes of the 7 ETR expression in KO and OE lines, revealed that other ETR expression is upregulated in KO mutants, which may explain the absence of obvious phenotype. and this suggest that SlETR7 maybe not critical in fruit ripening. Thirdly, regarding the studies of the seven tomato ETRs, one major bottleneck is the absence of reliable method to quantify them at the protein level. A targeted proteomic method was developed, PRM for Parallel Reaction Monitoring, and allow the identification and relative quantification of the seven tomato ETRs. This development applied to the study of the WT and Never Ripe mutant tomatoes showed that there is an over-accumulation of SlETR3, affected by a gain-of-function mutation in NR, while the NR tomatoes undergo ripening, which may be a cause of further ripening inhibition, as NR fruit stay orange. Finally, ETR mRNAs and proteins were analyzed within the same samples, and this led us to propose that there is a positive correlation between ETR mRNAs and proteins, which was controversial in the previous literature

Item Type:PhD Thesis
Uncontrolled Keywords:
Institution:Université de Toulouse > Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE)
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Research Director:
Chervin, Christian
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Deposited On:08 Apr 2020 10:28

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