Morphological, biochemical and transcriptomic characterisation of Chlorella sorokiniana and Chlorella zofingiensis during normal and stress conditions
Chlorella has been identified as one of the most interesting microalgae species, which has high nutritional values, high growth rate, and is able to produce a wide range of metabolites in response to environmental changes. The objectives of this study are to characterise the morphology and bio...
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| Format: | Thesis |
| Language: | English |
| Published: |
2017
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/69079/1/IB%202018%202%20IR.pdf |
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| Summary: | Chlorella has been identified as one of the most interesting microalgae species,
which has high nutritional values, high growth rate, and is able to produce a wide
range of metabolites in response to environmental changes. The objectives of
this study are to characterise the morphology and biochemical contents and to
identify the genes and miRNAs involved in regulating the production of
carotenoids and lipids in Chlorella sorokiniana and Chlorella zofingiensis when
cultured under high light intensity combined with glucose supplementation. In this
study, stress was introduced to the Chlorella cultures by adding 2% glucose and
increasing the light intensity from 10 to 100 μmol photons m-1 s-1. Then, the
pigments, total phenolic contents, and antioxidant activities of both Chlorella
species were evaluated. The results showed that both strains grew larger when
cultured under stress condition. Although the total carotenoid content was
increased under stress condition, reduction of the pigment and total phenolic
contents associated with lower antioxidant activity were also recorded.
Subsequently, the transcriptome of C. sorokiniana was sequenced using Illumina
paired-end sequencing, and 198,844,110 raw reads with the length of 100 bp
were produced. After pre-processing, ~95% of high quality reads were de novo
assembled using Trinity software into 18,310 contigs. Analysis of differential
gene expression by DESeq2 package showed that a total of 767 genes were
upregulated and 948 genes were downregulated in stress conditions. Then,
miRNAs that regulate the genes during normal and stress conditions of both C.
sorokiniana and C. zofingiensis were profiled and analysed using CLC Genomic
Workbench and OmiRas. From both analysis pipelines, the known and predicted
novel miRNAs were identified. Although most of the identified miRNAs were not
functionally determined, this study suggests that they were species-specific,
which may have roles in regulating genes during stress condition. In conclusion,
identifying the genes and the regulation of various metabolite productions under
different growth conditions are useful for further strain enhancement of the
microalgae. |
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