3.1. Transcriptome sequencing after silencing the ZcVgR gene
3.1.1. Summary of transcriptome sequencing data
Sequenced on the Illumina NovaSeq 6000 platform (Illumina, USA), the number of reads obtained for each treatment is shown in Table 1. The clean reads were then compared to the Z. cucurbitae genome, 25°C- siRNA obtained 33009994 (77.26%), 33383781 (78.92%), 38429125 (77.36%) reads, 25°C- CK obtained 42356023 (90.19%), 37587832 (84.41%), 32676853 (75.33%) reads, 45°C- siRNA obtained 32773661 (75.53%), 41186037 (87.81%), 30280609 (71.22%) reads, and 45°C- CK obtained 37803599 (85.43%), 40385695 (90.64%), 38368594 (86.77%) reads.
Table 1 Summary of the sequencing metrics of transcriptome
Samples
|
Repeats
|
Total raw reads
|
Total clean reads
|
Q20
(%)
|
Q30
(%)
|
GC
(%)
|
Total map
(Total mapped ratio)
|
25°C-
siRNA
|
1
|
42728176
|
42728176
|
97.78
|
93.53
|
40.26
|
33009994(77.26%)
|
2
|
43212556
|
42302242
|
97.87
|
93.81
|
40.78
|
33383781(78.92%)
|
3
|
50506270
|
49678102
|
97.96
|
93.99
|
39.94
|
38429125(77.36%)
|
25°C-
CK
|
1
|
48054180
|
46963052
|
96.25
|
89.98
|
41.39
|
42356023(90.19%)
|
2
|
46125726
|
44531204
|
96.46
|
90.42
|
41.75
|
37587832(84.41%)
|
3
|
44308522
|
43376432
|
97.72
|
93.41
|
40.19
|
32676853(75.33%)
|
45°C-
siRNA
|
1
|
44381518
|
43392714
|
97.25
|
93.41
|
40.1
|
32773661(75.53%)
|
2
|
47494150
|
46905948
|
98.07
|
94.04
|
42.02
|
41186037(87.81%)
|
3
|
43255216
|
42515658
|
96.95
|
91.66
|
39.28
|
30280609(71.22%)
|
45°C-
CK
|
1
|
45438266
|
44252034
|
96.21
|
89.95
|
41.45
|
37803599(85.43%)
|
2
|
45483036
|
44556024
|
97.42
|
93.16
|
41.61
|
40385695(90.64%)
|
3
|
45529354
|
44219650
|
95.93
|
89.33
|
41.08
|
38368594(86.77%)
|
3.1.2. Analysis of gene expression levels
A violin plot of the gene expression distribution showed that the total amount of gene expression data across samples was basically the same, and the overall expression level of genes was high (Fig. 1). The correlation heatmap between samples showed that the correlation between replicates of each sample was high and the similarity of expression patterns between replicates was high (Fig. 2).
The abscissa is the repeated number of the sample, and the ordinate is log2 (FPKM+1).
The horizontal and vertical coordinates are the squares of the correlation coefficients of each sample.
3.1.3. Analysis of Differential genes
After quantitative analysis of the gene expression levels of the samples, the differentially expressed genes were screened by Padj value <= 0.05 and │log2FC│ >= 1. The results showed that 702 differentially expressed genes were obtained by silencing the ZcVgR gene in the 25°C treatment, of which 57 genes were up-regulated and 645 genes were downregulated (Fig. 3A); 1633 differentially expressed genes were obtained by silencing the ZcVgR gene in the 45°C treatment, of which 774 genes were up-regulated and 859 genes were downregulated (Fig. 3B). After silencing the ZcVgR gene, the ZcVgR gene was significantly downregulated at the transcriptional level, and the expression of the ZcVgR gene of siRNA was highly significantly lower than that of CK in the 25°C treatment (Fig. 4A), and the expression of the ZcVgR gene of siRNA was also significantly lower than that of CK in the 45°C treatment (Fig. 4B).
3.1.4. Differential genes associated with reproduction and lifespan
Silencing the ZcVgR gene in the 25°C treatment, reproduction-related genes such as doublesex (dsx), juvenile hormone epoxide hydrolase (JHEH), octopamine receptor and troponin C (TnC) were significantly downregulated at the transcriptional level; insulin receptor (IR) and catalase genes were the main differentially expressed genes related to lifespan, both of which were downregulated differentially expressed genes (Table 2). More differentially expressed genes were obtained by silencing the ZcVgR gene in the 45°C treatment. The differentially expressed genes related to reproduction were mainly Vg, ecdysone-induced protein 74EF (Eip74EF), Krueppel homolog 1 (Kr-h1) and OTU-related genes, except for ZcVg3 and Eip74EF-related genes which were significantly upregulated, all other genes were downregulated differential genes; lifespan-related genes mainly included heat shock protein (HSP), IR and G protein-coupled receptor (GPCR) genes, among which HSP70, HSP27 and IR genes were downregulated differential genes, and HSP23-like and GPCR Mth2-like were upregulated differential genes (Table 3). VgR is a specific binding receptor for Vg (Tufail and Takeda, 2005), and silencing the ZcVgR gene in the 45°C treatment resulted in significant downregulation of the vitellogenin-1 (ZcVg1) gene and significant upregulation of the ZcVg3 gene, suggesting that ZcVg3 may be the major binding ligand for ZcVgR. Short-term high temperature treatment resulted in the up-regulation of the HSP70 gene in Z. cucurbitae as a means of reducing or avoiding the adverse effects of high temperature stress (Tan et al., 2023). Silencing the ZcVgR gene in the 45°C treatment resulted in a significant downregulation of the HSP70 gene, suggesting that silencing the ZcVgR gene indirectly reduces the heat resistance of female Z. cucurbita.
Table 2 The information of differential genes related to reproduction and lifespan generated by silencing the ZcVgR gene in the 25°C treatment
Gene name
|
Padj value
|
Result
|
Gene description
|
Gene family
|
LOC105217947
|
0.011896449
|
Down
|
protein doublesex%2C transcript variant X5
|
DM
|
LOC105221309
|
0.007912653
|
Down
|
juvenile hormone epoxide hydrolase 1
|
EHN
|
LOC114804176
|
0.038879653
|
Down
|
octopamine receptor beta-2R
|
7tm_1
|
LOC105216072
|
0.013288639
|
Down
|
troponin C%2C transcript variant X1
|
-
|
LOC105215909
|
0.036206178
|
Down
|
insulin receptor
|
-
|
LOC105217045
|
0.040395994
|
Down
|
catalase
|
Catalase
|
Table 3 The information of differential genes related to reproduction and lifespan generated by silencing the ZcVgR gene in the 45°C treatment
Gene name
|
Padj value
|
Result
|
Gene description
|
Gene family
|
LOC105213778
|
0.002325837
|
Down
|
vitellogenin-1
|
Lipase
|
LOC105213843
|
0.032862325
|
Up
|
vitellogenin-1-like
|
Lipase
|
Yp3_0
|
1.34E-13
|
Up
|
vitellogenin-3
|
Lipase
|
LOC105217947
|
0.011896449
|
Down
|
protein doublesex%2C transcript variant X5
|
DM
|
LOC105211529
|
0.000229115
|
Up
|
ecdysone-induced protein 74EF%2C transcript variant X2
|
-
|
Kr-h1_3
|
0.005627728
|
Down
|
Krueppel homolog 1%2C transcript variant X2
|
-
|
LOC105210596
|
0.000132832
|
Down
|
OTU domain-containing protein 4%2C transcript variant X1
|
OTU
|
LOC105215719
|
9.07E-12
|
Down
|
maternal effect protein oskar
|
-
|
LOC105216072
|
7.19E-08
|
Down
|
troponin C%2C transcript variant X1
|
-
|
LOC105209524
|
1.05E-08
|
Down
|
heat shock 70 kDa protein cognate 2
|
HSP70
|
LOC105220844
|
7.19E-08
|
Up
|
heat shock protein 23-like
|
-
|
Hsp27_0
|
2.68E-05
|
Down
|
heat shock protein 27
|
-
|
LOC105215909
|
1.25E-24
|
Down
|
insulin receptor
|
-
|
LOC105210455
|
8.12E-08
|
Up
|
G-protein coupled receptor Mth2-like%2C transcript variant X2
|
-
|
3.1.5. GO enrichment analysis of differential genes
GO enrichment analysis of the differentially expressed genes was then performed using Padj value < 0.05 as the threshold for significance enrichment, and filtered to show the top 30 GO terms, or all terms if there were less than 30. The results showed that the upregulated differentially genes obtained by silencing the ZcVgR gene in the 25°C treatment included 10 terms belonging to BP, 3 terms belonging to CC, and 10 terms belonging to MF, among which proteolysis, serine-type endopeptidase activity, serine-type peptidase activity, and serine hydrolase activity had the most upregulated differential genes with 3 genes (Fig. 5A); 10 term of the downregulated differential genes belonged to BP, 10 term belonged to CC, 10 term belonged to MF, with peptidase activity, acting on L-amino, and peptidase activity possessed the most downregulated differential genes with 72 genes (Fig. 5B). The upregulated differential genes obtained by silencing the ZcVgR gene in the 45°C treatment each had 10 terms belonging to BP, CC, and MF, of which peptidase activity had the most upregulated differential genes with 60 genes, followed by peptidase activity, acting on L-amino and proteolysis, with 59 upregulated differential genes (Fig. 5C); the downregulated differential genes each had 10 terms belonging to BP, CC and MF, with oxidoreductase activity having the most downregulated differential genes with 64 genes (Fig. 5D). In summary, silencing the ZcVgR gene resulted in upregulated differential genes mainly enriched in terms related to protein and amino acid hydrolysis, and downregulated differential genes mainly enriched in terms related to peptidase and oxidoreductase activity. GO function enrichment analysis of reproduction-related differentially expressed genes revealed that several differentially expressed genes, including the ZcVgR gene, were enriched in the calcium ion binding term (GO:0005509), which belongs to MF. Silencing the ZcVgR gene in the 25°C treatment resulted in the enrichment of 4 downregulated differentially expressed genes in the calcium ion binding term, including LOC105209324, LOC105211247, Egfl8_0, and LOC105217203 genes, mainly cadherin and EGF_CA family related genes; silencing the ZcVgR gene in the 45°C treatment resulted in 6 downregulated differential genes enriched in the calcium-binding term, including LOC105209324, LOC105211247, Egfl8_0, Srl_2 and LOC105215719 genes, mainly Cadherin and EGF_CA family related genes and TnC related genes.
3.1.6. KEGG pathway enrichment analysis of differential genes
Padj value < 0.05 was used as the threshold for significant enrichment. The differentially expressed genes were analysed by KEGG biochemical pathway analysis, and the 20 most significant KEGG pathways were selected to plot bubble plots, and if there were less than 20, all pathways were plotted. 2 of the upregulated differential genes obtained by silencing the ZcVgR gene in the 25°C treatment was enriched in the Toll and Imd signalling pathway (dme04624) and 1 in the Amino sugar and nucleotide sugar metabolism pathway (dme00520) (Fig. 6A); 16 of the downregulated differential genes were enriched in the Peroxisome pathway (dme04146), 13 in the Fatty acid metabolism pathway (dme01212), and 12 in the Carbon metabolism pathway (dme01200) (Fig. 6B). 14 of the upregulated differential genes obtained by silencing the ZcVgR gene in the 45°C treatment was enriched in the Toll and Imd signalling pathway (dme04624), and 10 in the Lysosome pathway (dme04142) (Fig. 6C); 15 of the downregulated differential genes were enriched in the Carbon metabolism pathway (dme01200), 11 in the Fatty acid metabolism pathway (dme01212), and 10 in the Oxidative phosphorylation pathway (dme00190) (Fig. 6D). The upregulated differential genes were mainly enriched in immune-related pathways, and the downregulated differential genes were mainly enriched in energy metabolism-related pathways.
3.2. Proteomic analysis after silencing the ZcVgR gene
3.2.1. Summary of Protein identification
The proteome after silencing the ZcVgR gene was analysed using the TMT quantitative proteomics method, and the number of peptides and proteins identified is shown in Table 4. 321710 validated profiles were obtained, with 18623 proteins and 257600 peptides identified, and the total number of proteins that could be quantified was 16517. The annotated sequences were compared with the genes in the COG classification (Fig. 7), in which general function prediction contained the highest number of sequences with 990, followed by post-translational modifications, protein transporters and chaperones with 737.
Table 4 Identification statistics of proteins
Total spectra
|
Matched spectrum
|
Peptide
|
Identified protein
|
ALL
|
524293
|
321710
|
257600
|
18623
|
16517
|
The repeatability Coefficient of Variance (CV) was analysed for each sample, and the cumulative plots of CV values of all proteins in the four samples were plotted and the results showed that the curves were all rapidly increasing, and that all four samples had good repeatability (Fig. 8).
The abscissa is the annotated functional classification, and the ordinate is the number of proteins annotated to the corresponding function.
3.2.2. Analysis of Differential protein
The quantified proteins were subjected to differential protein analysis, and upregulated differential proteins were screened by P value <= 0.05 and FC >= 1.5, and downregulated differential proteins were screened by P value <= 0.05 and FC <= 0.67. The results showed that 49 differential proteins were obtained by silencing the ZcVgR gene in the 25°C treatment, of which 23 were upregulated differential proteins and 26 were downregulated differential proteins (Fig. 9A). Silencing the ZcVgR gene in the 45°C treatment resulted in 1374 differential proteins, of which 600 were upregulated differential proteins and 774 were downregulated differential proteins (Fig. 9B). Silencing the ZcVgR gene in the 25°C (Fig. 10A) and 45°C (Fig. 10B) treatments, the ZcVgR gene was not significantly different from CK at the protein level. After silencing the ZcVgR gene, the ZcVgR gene was significantly downregulated at the transcriptional level, but there was no significant difference at the protein level, which may be due to the complex post-transcriptional processing mechanism and different proteins with different half-lives, leading to inconsistent expression of ZcVgR gene at the protein and mRNA levels (Luo et al., 2019).
3.2.3. Differential proteins associated with reproduction and lifespan
The number of reproductive-related differential proteins obtained by silencing the ZcVgR genes in the 25°C treatment was low, with only 1 upregulated differential protein (calcium-binding protein E63-1 isoform X3) and 1 downregulated differential protein (F-box only protein 32) (Table 5); silencing the ZcVgR gene in the 45°C treatment resulted in more reproductive and lifespan-related differential proteins, and the reproductive-related differential proteins were mainly Vg, OTU and TnC-related proteins, and all of them were upregulated differential proteins except TnC-related proteins which were significantly downregulated, and the lifespan-related proteins were mainly HSP and GPCR-related proteins, and all of them were upregulated differential proteins (Table 6). Among them, the expression trends of ZcVg3, TnC, HSP23-like and GPCR Mth2-like genes were consistent at both transcriptional and protein levels, and silencing the ZcVgR gene resulted in the significant upregulation of the ZcVg3 gene at both transcriptional and protein levels, further suggesting that ZcVg3 may be the main binding ligand of ZcVgR. The TnC gene was involved in the regulation of reproduction, and its downregulation suppressed egg-laying in female Z. cucurbitae; the GPCR Mth2-like gene was significantly upregulated at both the transcriptional and protein levels, and shortened the lifespan of female Z. cucurbitae. Studies have shown that the HSP23 gene is important for diapause in insects (Rinehart and Denlinger, 2000), so the HSP23-like genes may have similar regulatory functions affecting reproduction and lifespan in female Z. cucurbitae.
Table 5 The information of differential protein related to reproduction and lifespan generated by silencing the ZcVgR gene in the 25°C treatment
Protein
|
Pvalue
|
Result
|
Protein description
|
Gene
|
XP_028902016.1
|
0.013621843
|
Down
|
calcium-binding protein E63-1 isoform X3
|
LOC105221050
|
XP_011188571.1
|
0.006832998
|
Up
|
F-box only protein 32
|
LOC105216012
|
Table 6 The information of differential protein related to reproduction and lifespan generated by silencing the ZcVgR gene in the 45°C treatment
Protein
|
Pvalue
|
Result
|
Protein description
|
Gene
|
XP_011185138.1
|
0.006279213
|
Up
|
vitellogenin-3
|
Yp3_0
|
XP_028897205.1
|
0.036400419
|
Up
|
vitellogenin-1-like
|
LOC105213843
|
XP_028897575.1
|
0.000704419
|
Up
|
octopamine receptor beta-2R
|
LOC105214370
|
XP_011179957.1
|
2.46E-05
|
Up
|
OTU domain-containing protein 4 isoform X3
|
LOC105210596
|
XP_011188650.1
|
0.001277116
|
Down
|
troponin C isoform X1
|
LOC105216072
|
XP_011195675.1
|
0.0214973
|
Up
|
heat shock protein 23-like
|
LOC105220844
|
XP_011179738.1
|
0.028081399
|
Up
|
G-protein coupled receptor Mth2-like
|
LOC105210455
|
3.2.4. GO enrichment analysis of differential proteins
GO enrichment analysis was performed on the differential proteins, and the top 20 GO terms were screened for all three categories, and all terms were shown if there were less than 20. The results showed that among the upregulated differential proteins obtained by silencing the ZcVgR gene in the 25°C treatment, 3 terms belonged to BP, 1 term belonged to CC, and 1 term belonged to MF, of which the extracellular region had the most upregulated differential proteins with 2 proteins (Fig. 11A); among the downregulated differential proteins, 2 terms belonged to BP, no term belonged to CC, and 2 terms belonged to MF, of which sensory perception of taste, transcription corepressor activity, and calcium ion binding possessed the most downregulated differential proteins, all with 2 proteins (Fig. 11B). Among the upregulated differential proteins obtained by silencing the ZcVgR gene in the 45°C treatment, 20 terms belonged to BP, 2 terms belonged to CC, and 15 terms belonged to MF, of which localisation possessed the most upregulated differential proteins with 44 proteins (Fig. 11C); among the downregulated differential proteins, 20 terms belonged to BP, 9 terms belonged to CC, and 17 terms belonged to MF, of which membrane possessed the most downregulated differential proteins with 89 proteins (Fig. 11D).
3.2.5. KEGG pathway enrichment analysis of differential proteins
KEGG enrichment analysis was performed on the differential proteins, and the 20 most significant KEGG pathways were selected to be plotted in bubble maps, and if there were less than 20, all pathways were plotted. 1 upregulated differential protein obtained by silencing the ZcVgR gene in the 25°C treatment was enriched in the Galactose metabolism pathway (map00052) and 1 in the Starch and sucrose metabolism pathway (map00500) (Fig. 12A); 1 of the downregulated differential protein was enriched in the Phototransduction- fly pathway (map04745) (Fig. 12B). 13 of the upregulated differential proteins obtained by silencing the ZcVgR gene in the 45°C treatment was enriched in the Phagosome pathway (map04145) (Fig. 12C); 15 of the downregulated differential proteins were enriched in the Autophagy - animal pathway (map04140) (Fig. 12D). The differential proteins were mainly enriched in immune-related pathways and energy metabolism-related pathways.
3.3. Transcriptome and proteome correlation analysis
Correlation analysis of the transcriptome and proteome after silencing the ZcVgR gene in the 25°C treatment showed that 5 genes and proteins were differentially expressed at both the transcript and protein levels (Fig. 13A), and 168 genes and proteins were differentially expressed at both the transcript and protein levels in the 45°C treatment (Fig. 13B). The Pearson correlation test showed that the correlation between the proteome and the transcriptome was low, and the correlation between mRNAs with the same expression trend and their corresponding proteins was low, with a correlation of 0.04 in the 25°C treatment (Fig. 14A) and a correlation of 0.079 in the 45°C treatment (Fig. 14B), which may be due to translational regulation mechanisms and other reasons.