Ethephon Activates the Transcription of Senescence-Associated Genes and Nitrogen Mobilization in Grapevine Leaves (Vitis vinifera cv. Riesling)

Maximilian Hendgen,Stefan Günther,Sven Schubert,Otmar Löhnertz

doi:10.3390/plants10020333

Maximilian Hendgen, Stefan Günther + Show 2 more

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https://doi.org/10.3390/plants10020333

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Abstract

Nitrogen (N) remobilization in the context of leaf senescence is of considerable importance for the viability of perennial plants. In late-ripening crops, such as Vitis vinifera, it may also affect berry ripening and fruit quality. Numerous studies on the model plant Arabidopsis thaliana have confirmed an involvement of the plant hormone ethylene in the regulation of senescence. However, ethylene research on grapevine was mostly focused on its involvement in berry ripening and stress tolerance until now. To investigate the effect of ethylene on the initiation, regulation, and progress of senescence-dependent N mobilization in grapevine leaves, we treated field-grown Vitis vinifera cv. Riesling vines with 25 mM ethephon at the end of berry ripening. Ethephon induced premature chlorophyll degradation and caused a shift of the leaf transcriptome equivalent to developmental leaf senescence. The upregulated metabolic processes covered the entire N remobilization process chain, altered the amino acid composition in the leaves, and resulted in an average 60% decrease in leaf N. Our findings increase the fundamental knowledge about the initiation and manipulation of leaf N remobilization in perennial woody plants by ethephon. This offers a methodological approach to the targeted induction of senescence and thus to an improvement in the N supply of grapes.

Highlights

With more than 7.5 million hectares of cultivated cropland worldwide and an annual production of approximately 75 million tons of grapes, Vitis vinifera is a significant permanent crop and of interest for applied research [1]
Not much effort has been undertaken in investigating the hormonal regulation of grapevine leaf senescence, transcriptome studies have revealed a profound change in gene expression due to the initiation of this process [6]
The initiation of the senescence process leads to major alterations in gene transcription, in particular to the upregulation of senescenceassociated genes (SAGs), and in consequence to the degradation of chlorophyll, proteolysis, N remobilization and to the decay of the leaf cells [7,10,12]

Summary

Introduction

With more than 7.5 million hectares of cultivated cropland worldwide and an annual production of approximately 75 million tons of grapes (status 2017), Vitis vinifera is a significant permanent crop and of interest for applied research [1]. Senescence denotes the final developmental stage of a leaf’s lifecycle [7] It is a complex, genetically controlled aging process in plants that is triggered either developmentally by leaf age, or prematurely by external environmental factors such as, for example, drought or nutrient stress [8,9]. The aim is a recycling of nutrients—mainly nitrogen (N)—from the leaf into storage organs, as nutrient acquisition is an energyintensive process and nutrient recycling, represents an evolutionary advantage for plants [10,11] Both the rapidity of leaf aging and the integration of environmental factors are controlled by phytohormones [8]. The initiation of the senescence process leads to major alterations in gene transcription, in particular to the upregulation of senescenceassociated genes (SAGs), and in consequence to the degradation of chlorophyll, proteolysis,

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