A High Temperature Environment Regulates the Olive Oil Biosynthesis Network.

Yael Nissim,Zohar Kerem,Ran Hovav,Iris Biton,Yair Many,Benjamin Avidan,Giora Ben-Ari,Adi Doron-Faigenboim,Maya Shlosberg

doi:10.3390/plants9091135

Abstract

Climate change has been shown to have a substantial impact on agriculture and high temperatures and heat stress are known to have many negative effects on the vegetative and reproductive phases of plants. In a previous study, we addressed the effects of high temperature environments on olive oil yield and quality, by comparing the fruit development and oil accumulation and quality of five olive cultivars placed in high temperature and moderate temperature environments. The aim of the current study was to explore the molecular mechanism resulting in the negative effect of a high temperature environment on oil quantity and quality. We analyzed the transcriptome of two extreme cultivars, ‘Barnea’, which is tolerant to high temperatures in regard to quantity of oil production, but sensitive regarding its quality, and ‘Souri’, which is heat sensitive regarding quantity of oil produced, but relatively tolerant regarding its quality. Transcriptome analyses have been carried out at three different time points during fruit development, focusing on the genes involved in the oil biosynthesis pathway. We found that heat-shock protein expression was induced by the high temperature environment, but the degree of induction was cultivar dependent. The ‘Barnea’ cultivar, whose oil production showed greater tolerance to high temperatures, exhibited a larger degree of induction than the heat sensitive ‘Souri’. On the other hand, many genes involved in olive oil biosynthesis were found to be repressed as a response to high temperatures. OePDCT as well as OeFAD2 genes showed cultivar dependent expression patterns according to their heat tolerance characteristics. The transcription factors OeDof4.3, OeWRI1.1, OeDof4.4 and OeWRI1.2 were identified as key factors in regulating the oil biosynthesis pathway in response to heat stress, based on their co-expression characteristics with other genes involved in this pathway. Our results may contribute to identifying or developing a more heat tolerant cultivar, which will be able to produce high yield and quality oil in a future characterized by global warming.

Highlights

Abiotic stresses, including high temperatures have a substantial negative impact on the reproductive phase of the plant
We have lately addressed the effect of high temperature environments on olive oil yield and quality, by comparing the fruit development and oil accumulation and quality of five olive cultivars placed in high temperature (HT) and low temperature (MT) environments [36]
Our study demonstrates the negative effect of a high temperature environment on several key genes critical to the production and quality of olive oil

Summary

Introduction

Abiotic stresses, including high temperatures have a substantial negative impact on the reproductive phase of the plant. Oilseed crops are negatively affected by heat stress, which has been shown to reduce starch, protein and oil content [1,2]. The reproductive phase of plant development is more sensitive to high temperatures than the vegetative phase, causing a reduction in yield [8]. Yield reduction in response to heat stress or high temperatures has been reported in wheat, peanut, rice bean and tomato [9–13]. Olive oil accumulation in the mesocarp cells of the fruit is influenced by cultivar type and climactic conditions. It occurs mainly during the summer and decreases during fruit ripening in the fall [14,15]

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