Characterization of lipases and lipids in oat varieties during seed germination
(2023)Pure and Applied Biochemistry
- Abstract
- Oats (Avena sativa) are a cereal crop rich in dietary fibre, vitamins, antioxidants, and other nutrients. It is considered to have higher nutritional values compared to other cereals, with a higher fat content (2-13%). Oats also have high content of lipase enzymes when compared to other crops. The high lipase activity is unwanted in oats as it may induce hydrolytic rancidity, with a soapy, bitter flavor in oat products. However, lipases may be important in seed germination, to degrade lipids to supply carbon and energy for plant growth. The lipases active in mature seeds and during germination, as well as their correlation with lipid synthesis and content, are currently not well studied in oats. Thus, a better understanding of the... (More)
- Oats (Avena sativa) are a cereal crop rich in dietary fibre, vitamins, antioxidants, and other nutrients. It is considered to have higher nutritional values compared to other cereals, with a higher fat content (2-13%). Oats also have high content of lipase enzymes when compared to other crops. The high lipase activity is unwanted in oats as it may induce hydrolytic rancidity, with a soapy, bitter flavor in oat products. However, lipases may be important in seed germination, to degrade lipids to supply carbon and energy for plant growth. The lipases active in mature seeds and during germination, as well as their correlation with lipid synthesis and content, are currently not well studied in oats. Thus, a better understanding of the processes in the germinating plant is required.
This project aimed to characterize lipases and lipid synthesis gene’s role up to seven days of germination and identify lipases of important in the mature kernel. The large differences in lipid content found among oat cultivars emphasize the need of choosing three distinct cultivars to investigate their lipid metabolism and potential health advantages. The relationship between lipase activity and lipid content, of cultivar Belinda and selected oat lines with low (cv. Galant) and high (cv. Fatima) lipid content, was carried out. Lipase activity was measured, fluorometrically and in-gel, with 4-methylumbelliferone heptanoate (MUH) as substrate and lipid content was analyzed using lipid extraction and analysis of methylated fatty acids using gas chromatography. qPCR analysis was used to measure the relative expression of selected lipid biosynthesis and lipase genes in one of the oat varieties, cv Belinda.
In all varieties the total lipase activity was shown to increase upon germination. The lipase activity differed depending on time point and tissue, with no apparent correlation to lipid concentration. On day four of germination, gene expression analysis showed that some genes involved in the breakdown of storage lipids, as well as those to produce membrane and cellular lipids, are upregulated. The total lipid content, in Belinda and all oat cultivars, remained steady during germination, with variations in the fatty acid ratio and the tissue examined, such as roots and leaves. Palmitic acid (C16:0), linoleic acid (C18:2), and oleic acid (C18:1) were the principal fatty acids that accumulated in mature seed, with a detectable increase of the latter two during germination. Our results support the theory that lipases are important for an active turnover of storage lipids in germinating oats. (Less) - Popular Abstract
- Oats (Avena sativa) are part of the cereal whole grain family, and their production has risen for the past few years due to extensive research done on the health benefits to humans. Oats are often consumed as whole grains, and are a good source of fiber, unsaturated fatty acids, vitamins, antioxidants, and minerals. Moreover, oats contain beta-glucans that are dietary fibers that help in maintaining healthy regulation of cholesterol, sugar levels. Oats may further be part of a gluten free diet. Oats are higher in lipid than other cereals, which has drawbacks when it comes to storage stability. During storage they may develop off-flavors, rendering them unfit for human consumption, as a result from changes in the lipids. The decrease in... (More)
- Oats (Avena sativa) are part of the cereal whole grain family, and their production has risen for the past few years due to extensive research done on the health benefits to humans. Oats are often consumed as whole grains, and are a good source of fiber, unsaturated fatty acids, vitamins, antioxidants, and minerals. Moreover, oats contain beta-glucans that are dietary fibers that help in maintaining healthy regulation of cholesterol, sugar levels. Oats may further be part of a gluten free diet. Oats are higher in lipid than other cereals, which has drawbacks when it comes to storage stability. During storage they may develop off-flavors, rendering them unfit for human consumption, as a result from changes in the lipids. The decrease in oats quality is in large part due to a class of enzymes known as lipases. The oat lipids are degraded by lipases into undesirable free fatty acids. To prevent that, these enzymes are therefore rendered inactive by heat treatment prior to storage. Although it has been suggested that oats with lower lipase activity may have improved storage stability and so be a substitute for the heat treatment, it is unknown which lipases would need to be reduced to produce such oat. However, lipases are also crucial for seed germination and currently little is known about how lipases affect oat lipids and their role in germination.
In this study, we investigated the role of lipases during germination as well as which lipase(s) are active in the oat seed. The primary goal of the study has been to find out whether there is a correlation between lipase activity and the expression of lipase genes during germination. Further we have wanted to see how this relates to lipid content and expression of lipid biosynthesis genes involved in lipid production. Investigating this has been a major part of the study. In addition, a novel method for the detection of lipases in mature seed by in gel detection has also been tested.
Lipases and lipid synthesis genes have been characterized by up to seven days of germination, in different tissues. By measuring enzyme activity, we could see an evident increase in activity during germination and a detectable band of lipase activity in gel. Several genes involved in the synthesis of membrane and cellular lipids and breakdown of storage lipids, were found to be upregulated at the same timepoint as the lipase activity increased, the gene expression being examined using qPCR analysis. The lipid content was another significant factor that was examined. It remained constant during germination with variations in the ratio of fatty acids. Gas chromatography was used to evaluate these two parameters.
Since lipases significantly affect oat quality, it is important to produce low-lipase oats. In this study several putative lipase genes have been identified to be upregulated during germination. Further, a soluble oat protein with lipase activity has been found. Taken together, these results increase the understanding of the role of lipases and lipids during oat germination and are an important step in determining what lipases may be the best to target for low-lipase oats in the future. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9116814
- author
- Muñoz Martín, Gloria LU
- supervisor
-
- Sofia Marmon LU
- organization
- year
- 2023
- type
- H2 - Master's Degree (Two Years)
- subject
- keywords
- Oats, lipase activity, gene expression, total lipids, fatty acids, Biotechnology, Gas Chromatography, food technology, biochemistry, applied biochemistry
- language
- English
- id
- 9116814
- date added to LUP
- 2023-05-26 09:09:08
- date last changed
- 2023-05-26 09:09:08
@misc{9116814,
abstract = {{Oats (Avena sativa) are a cereal crop rich in dietary fibre, vitamins, antioxidants, and other nutrients. It is considered to have higher nutritional values compared to other cereals, with a higher fat content (2-13%). Oats also have high content of lipase enzymes when compared to other crops. The high lipase activity is unwanted in oats as it may induce hydrolytic rancidity, with a soapy, bitter flavor in oat products. However, lipases may be important in seed germination, to degrade lipids to supply carbon and energy for plant growth. The lipases active in mature seeds and during germination, as well as their correlation with lipid synthesis and content, are currently not well studied in oats. Thus, a better understanding of the processes in the germinating plant is required.
This project aimed to characterize lipases and lipid synthesis gene’s role up to seven days of germination and identify lipases of important in the mature kernel. The large differences in lipid content found among oat cultivars emphasize the need of choosing three distinct cultivars to investigate their lipid metabolism and potential health advantages. The relationship between lipase activity and lipid content, of cultivar Belinda and selected oat lines with low (cv. Galant) and high (cv. Fatima) lipid content, was carried out. Lipase activity was measured, fluorometrically and in-gel, with 4-methylumbelliferone heptanoate (MUH) as substrate and lipid content was analyzed using lipid extraction and analysis of methylated fatty acids using gas chromatography. qPCR analysis was used to measure the relative expression of selected lipid biosynthesis and lipase genes in one of the oat varieties, cv Belinda.
In all varieties the total lipase activity was shown to increase upon germination. The lipase activity differed depending on time point and tissue, with no apparent correlation to lipid concentration. On day four of germination, gene expression analysis showed that some genes involved in the breakdown of storage lipids, as well as those to produce membrane and cellular lipids, are upregulated. The total lipid content, in Belinda and all oat cultivars, remained steady during germination, with variations in the fatty acid ratio and the tissue examined, such as roots and leaves. Palmitic acid (C16:0), linoleic acid (C18:2), and oleic acid (C18:1) were the principal fatty acids that accumulated in mature seed, with a detectable increase of the latter two during germination. Our results support the theory that lipases are important for an active turnover of storage lipids in germinating oats.}},
author = {{Muñoz Martín, Gloria}},
language = {{eng}},
note = {{Student Paper}},
title = {{Characterization of lipases and lipids in oat varieties during seed germination}},
year = {{2023}},
}