Changes in gene expression in potato meristems treated with the sprout suppressor 1,4-dimethylnaphthalene are dependent on tuber age and dormancy status.

Michael A Campbell,Carley Gwin,Rachael Adams,Helen H Tai,Mayank Gururani

doi:10.1371/journal.pone.0235444

Michael A Campbell, Carley Gwin + Show 3 more

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https://doi.org/10.1371/journal.pone.0235444

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Abstract

Commercial storage of potatoes often relies on the use of sprout inhibitors to prolong storage and reduce spoilage. The compound 1,4-dimethylnaphthalene (DMN) has seen increase application as a sprout inhibitor in the potato industry as older chemistries are being phased out. The mode of action of DMN is poorly understood as is the sensitivity of potato tissues to this new class of inhibitor. During storage potato tubers transition from a state of endo-dormant to eco-dormant and it is not known if the DMN response is consistent across this developmental transition. RNA-seq gene expression profiling was used to establish if stored potato tubers (Solanum tuberosum cv La Chipper) have differential sensitivity to DMN as tubers age. DMN was applied at three different times during storage; just after harvest when tubers are in endo-dormancy, midwinter at early eco-dormancy, and in spring during late eco-dormancy when sprouting was prevented via exposure to cold storage temperatures. Changes in gene expression were lowest during endo-dormancy while midwinter and spring treatments exhibited a greater and more diverse expression response. Functional analysis of differential gene expression demonstrated gene sets associated with DNA replication, cell division, and DNA methylation are suppressed after DMN treatment. However, gene sets associated with salicylic acid, jasmonic acid, abiotic and biotic stress responses are elevated by DMN only after endodormancy terminates. Gene clusters associated with pathogenesis related proteins PR-4 and PR-5 are also upregulated in response to DMN. These results indicate that DMN sensitivity changes as potato tubers age and transition from endo-dormant to eco-dormant in storage and the overall response is a shift in gene classes that regulate growth and response to stress.

Highlights

Per ton Potato is among the top five crops produced in the world
Genetic studies do not support the hypothesis that DMN prolongs a dormant state, but they do show that DMN exposure results in changes in genes associated with the regulation of cell division, suggesting a mechanism for growth suppression [5, 6]
There was no significant difference between the amount and quality of RNA isolated from control or DMN treated tuber tissue demonstrating that the application of the sprout inhibitor did not alter RNA stability or alter global stability of cellular transcripts

Summary

Introduction

Per ton Potato is among the top five crops produced in the world (http://www.fao.org/3/ai4691e.pdf). The compound 1,4-dimethylnaphthalene (DMN), originally isolated from tubers in storage, has been shown to be an effective inhibitor of sprout growth [2, 3]. DMN has been shown to be effective when applied to seed potatoes, some changes in tuber size in the following crop were detected [4]. Previous studies found changes in gene expression in tuber meristems are associated with DMN exposure, but those studies involved a single application of DMN to endo-dormant tubers [5], a situation that does not mimic the multiple applications of DMN that occur during commercial storage. Genetic studies do not support the hypothesis that DMN prolongs a dormant state, but they do show that DMN exposure results in changes in genes associated with the regulation of cell division, suggesting a mechanism for growth suppression [5, 6]

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