Chilling and Freezing Temperature Stress Differently Influence Glucosinolates Content in Brassica oleracea var. acephala.

Valentina Ljubej,Sanja Roje,Ivana Radojčić Redovniković,Dunja Šamec,Ana Smolko,Branka Salopek-Sondi

doi:10.3390/plants10071305

Abstract

Brassica oleracea var. acephala is known to have a strong tolerance to low temperatures, but the protective mechanisms enabling this tolerance are unknown. Simultaneously, this species is rich in health-promoting compounds such as polyphenols, carotenoids, and glucosinolates. We hypothesize that these metabolites play an important role in the ability to adapt to low temperature stress. To test this hypothesis, we exposed plants to chilling (8 °C) and additional freezing (−8 °C) temperatures under controlled laboratory conditions and determined the levels of proline, chlorophylls, carotenoids, polyphenols, and glucosinolates. Compared with that of the control (21 °C), the chilling and freezing temperatures increased the contents of proline, phenolic acids, and flavonoids. Detailed analysis of individual glucosinolates showed that chilling increased the total amount of aliphatic glucosinolates, while freezing increased the total amount of indolic glucosinolates, including the most abundant indolic glucosinolate glucobrassicin. Our data suggest that glucosinolates are involved in protection against low temperature stress. Individual glucosinolate species are likely to be involved in different protective mechanisms because they show different accumulation trends at chilling and freezing temperatures.

Highlights

Vegetables from the Brassica oleracea subgroup Acephala originated in the Mediterranean region but gained popularity worldwide [1]
In our study we sought to determine the levels of bioactive compounds in B. oleracea var. acephala under low temperature stress to narrow down the individual species that may be involved in the interaction
In our study, we determined the content of proline, chlorophylls, carotenoids, polyphenols, and glucosinolates in B. oleracea var. acephala plants subjected to chilling and freezing temperature stress under controlled laboratory conditions

Summary

Introduction

Vegetables from the Brassica oleracea subgroup Acephala originated in the Mediterranean region but gained popularity worldwide [1]. Plants respond to stress conditions with changes in the expression pattern of genes encoding proteins that control the biosynthesis of metabolites involved in the interactions between a given plant and its environment. This is an effort by plants to maximize their chances of survival under stress and maintain cellular function by synthesizing basic metabolites required for survival (primary metabolism) and specialized metabolites for specific environmental interactions (specialized metabolism). Specialized metabolites play critical roles in various physiological and pathological processes by participating in biochemical reactions required for proper biological function [7,8]

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Discussion

Conclusion