4. Analysis of gene expression related to phycocyanin synthesis
by rGO-TiO2
The regulation of the metabolic synthesis of phycocyanin inFACHB-314 can be assessed by gene expression level analysis. In
this study, we choose three key synthetase enzymes that can regulate the
synthesis of phycocyanin: The gene encodes urinary hyaluronan III
synthase (CobA-hemG), which can promote the production of urobilin III,
which is an important tetrapyrrole intermediate, including the synthesis
of chlorophyll, vitamin B12, heme and bilinin (Doan et al., 2021; Faieta
et al., 2021). HemG gene encodes protoporphyrinogen IX oxidase, which
can catalyze oxidized protoporphyrinogen IX to produce protoporphyrin IX
(Li et al., 2017; Lupatini et al., 2017). The gene encodes heme
oxygenase (Ho), which catalyzes the opening of the heme ring structure
to form chlorophyll IX, an intermediate in the biosynthesis of bilinin
(Liu et al., 2019; Rosa et al., 2019). Under the same conditions,
compare the control group and the nanoparticle addition experimental
group, and evaluate the regulation and influence mechanism of the
material on the synthesis of phycocyanin from the gene expression level
as shown in Figure 12 (a).
Figure 12 (b) shows the effect of the phycocyanin synthesis and
metabolism pathway in FACHB-314 cells on the gene expression
levels of CobA-hemG, HemG and Ho three enzyme proteins after the
experimental group and the control group were cultured for 72 hours.
Compared with the control group, the transcript expression levels of
CobA-hemG, HemG and ho genes in the FACHB-314 group containing
rGO-TiO2 composite nanoparticles were significantly
higher than those in the control group, which were 7.57, 5.65 and 3.33
times. The significant differences in the transcriptional expression
levels of the three key genes in the phycocyanin synthesis pathway can
be explained as follows: the mechanism of rGO-TiO2photocatalytic nanoparticles to promote phycocyanin synthesis inFACHB-314 cells is by stimulating the overexpression of genes
encoding key enzymes in the biosynthetic pathway of phycocyanin, thereby
promoting a lot of synthesis of CobA-hemG, HemG, and Ho enzyme proteins
during the synthesis and metabolism of phycocyanin. Furthermore, theFACHB-314 of the experimental group was induced to increase the
accumulation of phycocyanin. The results of the difference in
phycocyanin gene expression between the experimental group and the
control group are consistent with the above results, that is,
rGO-TiO2 photocatalytic nanoparticles can significantly
increase the content of phycocyanin in FACHB-314 under red light
conditions. The above results clarify from the level of gene
transcription and expression that rGO-TiO2photocatalytic nanoparticles sequentially promote the synthesis of
uroporphyrinogen III, protoporphyrin IX and biliverdin IX intermediates
through enzymatic reactions, thereby increasing the synthesis of
phycocyanin.