transcription PCR (qRT-PCR) in L. punctata
0202. Another independent research on qRTPCR assay for the expression of key starch
biosynthesis enzymes, including AGPase, soluble starch synthase (SSS), starch degradation
enzymes (SDE), and alpha- and beta-amylase,
under nitrogen (N) and phosphorus (P) deficiency condition was consistent with this RNASeq data (Zhao et al. 2015). Those studies provided a comprehensive transcriptome analysis of
L. punctata 0202 under nutrient starvation, which
indicated that nutrient starvation down-regulated
the global metabolic status and redirected metabolic flux of fixed CO 2 to starch biosynthesis
pathway. It provided a valuable genomic
resource for duckweed and paved the way for
further molecular biological studies and the
application of duckweed as a bioenergy crop
(Tao et al. 2013).
Not only nutrient starvation but also uniconazole can improve the starch content. Uniconazole
is a plant growth retardant, which can increase
starch and biomass accumulation of L. punctata
simultaneously under eutrophic conditions. The
result of transcriptome sequencing of uniconazole
application on fronds of L. punctata 0202
revealed the expression of genes involved in
endogenous hormones and chlorophyll biosynthesis pathway changed responsively. The dry
weight following the uniconazole treatment
increased by 10% compared to the controls at
240 h, resulting from the uniconazole affecting
endogenous hormones content, chlorophyll content, and the net photosynthetic rate. The dry
weight starch content increased up to 48% compared to 15.7% in the control group after 240 h
growth. Transcriptome sequencing revealed that
the expression of regulatory elements of hormone
signaling pathways that are involved in chlorophyll and starch metabolism changed correspondingly. Importantly, the expression of key
enzymes responsible for starch biosynthesis was
up-regulated, and transcript-encoding enzymes
involved in starch degradation and other
carbohydrate
metabolic
branches
were
down-regulated (Liu et al. 2015a, b).
According to current research on L. punctata
0202 starch accumulation, starch content could
reach up to approximately 45% (dry weight)
within 7 days under nutrient starvation condition
(Tao et al. 2013; Huang et al. 2014) and
approximately 48% (dry weight) within 10 days
under uniconazole treatment (Liu et al. 2015a, b).
A combined treatment of nutrient starvation and
uniconazole application or others to L. punctata
0202 is considered a promising method to further
improve the starch content. To support this, more
tests should be carried out to verify the hypothesis in the future. According to the latest study,
the starch content can reach 60% under nitrogen
starvation in the presence of exogenously applied
sucrose condition in Lemna aequinoctialis 6000
after treatment for 9 days. In this study, a combined transcriptome and metabolites analysis was
carried out for metabolic flux in starch accumulation. The researchers evaluated expression of
the genes involved in nitrogen metabolism, protein and amino acid metabolism, starch and
sucrose metabolism, and lipid metabolism by
sampling 7-day in time course under nitrogen
starvation condition. The expression of genes
encoding nitrate reductase, glutamine synthetase,
and glutamate synthase was down-regulated; the
expression of genes encoding enzymes involved
in gluconeogenesis was up-regulated, whereas
the majority of unigenes involved in glycolysis
were down-regulated. The metabolome analysis
revealed that more ADP-Glc was accumulated
and lower levels of UDP-Glc were accumulated,
which was consistent with the transcriptome
results. The activity of AGPase involved in
starch biosynthesis was significantly increased
while the activity of UGPase was dramatically
decreased. This study serves as an excellent
candidate for functional transcriptome study and
metabolic engineering to improve the production
of next-generation biofuels in duckweeds (Yu
et al. 2017).
128
Y. Fang et al.
0202. Another independent research on qRTPCR assay for the expression of key starch
biosynthesis enzymes, including AGPase, soluble starch synthase (SSS), starch degradation
enzymes (SDE), and alpha- and beta-amylase,
under nitrogen (N) and phosphorus (P) deficiency condition was consistent with this RNASeq data (Zhao et al. 2015). Those studies provided a comprehensive transcriptome analysis of
L. punctata 0202 under nutrient starvation, which
indicated that nutrient starvation down-regulated
the global metabolic status and redirected metabolic flux of fixed CO 2 to starch biosynthesis
pathway. It provided a valuable genomic
resource for duckweed and paved the way for
further molecular biological studies and the
application of duckweed as a bioenergy crop
(Tao et al. 2013).
Not only nutrient starvation but also uniconazole can improve the starch content. Uniconazole
is a plant growth retardant, which can increase
starch and biomass accumulation of L. punctata
simultaneously under eutrophic conditions. The
result of transcriptome sequencing of uniconazole
application on fronds of L. punctata 0202
revealed the expression of genes involved in
endogenous hormones and chlorophyll biosynthesis pathway changed responsively. The dry
weight following the uniconazole treatment
increased by 10% compared to the controls at
240 h, resulting from the uniconazole affecting
endogenous hormones content, chlorophyll content, and the net photosynthetic rate. The dry
weight starch content increased up to 48% compared to 15.7% in the control group after 240 h
growth. Transcriptome sequencing revealed that
the expression of regulatory elements of hormone
signaling pathways that are involved in chlorophyll and starch metabolism changed correspondingly. Importantly, the expression of key
enzymes responsible for starch biosynthesis was
up-regulated, and transcript-encoding enzymes
involved in starch degradation and other
carbohydrate
metabolic
branches
were
down-regulated (Liu et al. 2015a, b).
According to current research on L. punctata
0202 starch accumulation, starch content could
reach up to approximately 45% (dry weight)
within 7 days under nutrient starvation condition
(Tao et al. 2013; Huang et al. 2014) and
approximately 48% (dry weight) within 10 days
under uniconazole treatment (Liu et al. 2015a, b).
A combined treatment of nutrient starvation and
uniconazole application or others to L. punctata
0202 is considered a promising method to further
improve the starch content. To support this, more
tests should be carried out to verify the hypothesis in the future. According to the latest study,
the starch content can reach 60% under nitrogen
starvation in the presence of exogenously applied
sucrose condition in Lemna aequinoctialis 6000
after treatment for 9 days. In this study, a combined transcriptome and metabolites analysis was
carried out for metabolic flux in starch accumulation. The researchers evaluated expression of
the genes involved in nitrogen metabolism, protein and amino acid metabolism, starch and
sucrose metabolism, and lipid metabolism by
sampling 7-day in time course under nitrogen
starvation condition. The expression of genes
encoding nitrate reductase, glutamine synthetase,
and glutamate synthase was down-regulated; the
expression of genes encoding enzymes involved
in gluconeogenesis was up-regulated, whereas
the majority of unigenes involved in glycolysis
were down-regulated. The metabolome analysis
revealed that more ADP-Glc was accumulated
and lower levels of UDP-Glc were accumulated,
which was consistent with the transcriptome
results. The activity of AGPase involved in
starch biosynthesis was significantly increased
while the activity of UGPase was dramatically
decreased. This study serves as an excellent
candidate for functional transcriptome study and
metabolic engineering to improve the production
of next-generation biofuels in duckweeds (Yu
et al. 2017).
128
Y. Fang et al.