Transcriptome sequencing reveals potential key genes of cellular changes during the first rapid growth stage of jujube fruit size

Cell number and size are essential factors in determining the final size of the fruit. However, studies on the cellular changes and molecular mechanisms of jujube fruit size development are still unclear. In this study, changes in fruit length, width, weight, and corresponding mesocarp cells were measured during jujube fruit development. The results showed that cell division and cell expansion jointly participated in the first rapid growth stage of fruit size, and cell expansion was the main factor in the second rapid growth stage of fruit size. In a further study, transcriptome sequencing was used to analyse the expression profile of fruit size's first rapid growth stage. Most of these DEGs were assigned to seven significant trends. Three genes related to the auxin signal transduction pathway and three genes related to the brassinosteroid biosynthesis signal transduction pathway were detected to be directly related to cell enlargement and cell division, respectively, which may regulate the first rapid growth of fruit size. In conclusion, candidate genes were provided for regulating fruit size in this study, which is beneficial for analysing the molecular mechanism of fruit size and lays a foundation for breeding large-fruit jujube cultivars.</p

miR-155 post-transcriptionally represses Rheb expression by targeting its 3′UTR.

<p>(A) Sequences of mouse and human miR-155 and their predicted interactions with conserved 7-mer 1A miR-155 seeds found within the Rheb 3′UTRs of different species are shown. The sequence of the Rheb 3′UTR seed mutant used for the reporter assays and the predicted disruption of the miR-155 interaction are also shown. (B) RAW264.7 cells were co-transfected with control or miR-155 mimic and a wild-type (WT-Rheb) or mutated Rheb 3′UTR (mut-Rheb) luciferase reporter plasmid and assessed for luciferase activity at 24 h after transfection. Data are shown as the mean ± SEM of three independent experiments. ***, p<0.001; NS, not significant. (C–F) RAW264.7 cells were transfected with miR-155 mimic (C and E) or inhibitor (D and F) for 24 h and either left uninfected or infected with BCG. Protein expression levels of Rheb were detected by Western-blot. Values of Rheb/β-actin ratios are indicated below the representative blot (C and D), and expression levels of Rheb mRNA were detected by RT-PCR (E and F).</p

miR-155 promotes mycobacterial phagosome maturation.

<p>RAW 264.7 cells were transiently transfected with control or miR-155 mimic for 24 h and then infected with Texas Red-labeled BCG for 1 h. Lysosomes were immunolabeled with CD63 antibody followed by Alexa Fluor 488-conjugated goat anti-rabbit IgG antibody (A), or labeled with a fluorogenic substrate for proteases, DQ-Green (C). The colocalization of BCG with lysosome was detected by confocal microscopy. The percentage of co-localization of BCG with CD63-positive (B) or DQ-Green labeled (D) lysosomes was quantified, respectively. Cells treated with rapamycin were used as a positive control. Arrows indicate the co-localization of BCG with lysosomes; scale bar = 5 µm. Quantification of data are shown as the mean ± SEM of three independent experiments (n = 100 phagosomes). **, p<0.01.</p

miR-155-induced autophagy promotes the elimination of intracellular mycobacteria.

<p>(A and B) RAW 264.7 cells were transiently transfected with control or miR-155 mimic for 24 h, and then incubated with DMSO or 3-MA for 2 h. Protein levels of LC3 were detected by Western-blot in uninfected cells (A). Intracellular mycobacterial viability was determined at the indicated timepoints by CFU assay after BCG challenge for 1 h (B). (C and D) RAW 264.7 cells were transiently co-transfected with control or miR-155 mimic together with a control siRNA or Atg7 siRNA. The expression levels of Atg7 and LC3 were detected by Western-blot (C). Intracellular mycobacterial viability was determined by CFU assay at the indicated time after challenging with BCG for 1 h (D). Values of LC3-II/β-actin ratios are indicated below the representative blot. Data are shown as the mean ± SEM of three independent experiments. *, p<0.05; **, p<0.01; NS, not significant.</p

miR-155-induced autophagy promotes the co-localization of BCG with autophagosomes by suppressing Rheb expression.

<p>(A) RAW264.7 cells were transfected with a plasmid expressing Rheb for 24 h, and then incubated with DMSO or BafA. for 2 h. The expression levels of Rheb and LC3 were detected by Western-blot. Values of LC3-II/β-actin ratios are indicated below the representative blot. (B and C) RAW264.7 cells were co-transfected with control or miR-155 mimic together with a control plasmid or a plasmid expressing Rheb for 24 h, and then infected with Texas Red-labeled BCG for 1 h. The co-localization of BCG and MDC-labeled autophagosome was detected by confocal microscopy. Arrows indicate Quantification of BCG co-localization with autophagosomes described in B is shown (C). (D) RAW264.7 cells were co-transfected with control or miR-155 mimic together with a control plasmid or a plasmid expressing Rheb for 24 h. Cells were infected with BCG for 1 h, and washed for three times to remove extracellular mycobacteria. Intracellular mycobacterial viability was determined by CFU assay at the indicated timepoints. Data are shown as the mean ± SEM of three independent experiments. *, p<0.05; **, p<0.01; NS, not significant.</p

miR-155-induced autophagy promotes the formation of mycobacterial autophagosomes.

<p>(A) RAW264.7 cells stably expressing GFP-LC3 were transiently transfected with control or miR-155 mimic and then infected with Texas Red-labeled BCG for 1 h. The co-localization of BCG with LC3 was detected by confocal microscopy. (B) Quantification of the co-localization of BCG with LC3-positive autophagosomes is shown. (C) RAW264.7 cells were transiently transfected with control or miR-155 mimic, and then infected with Texas Red-labeled BCG for 1 h. Endogenous LC3 was stained with LC3 antibody followed by Alexa Fluor 488-conjugated goat anti-rabbit IgG (Green). The co-localization of BCG with endogenous LC3 was detected by confocal microscopy. (D) Quantification of the co-localization of BCG with LC3-positive autophagosomes is shown. (E) After transient transfection with control or miR-155 mimic, RAW264.7 cells were infected with Texas Red-labeled BCG for 1 h, and then were labeled with a specific fluorescent dye MDC (50 µM) for autophagic vacuoles. The co-localization of BCG with MDC-positive autophagic vacuoles was detected by confocal microscopy. (F) Quantification of the co-localization of BCG with MDC-positive autophagosomes is shown. Cells treated with rapamycin were used as a positive control. Arrows indicate the co-localization of BCG with autophagosomes; scale bar = 5 µm. Data are shown as the mean ± SEM of three independent experiments (n = 100 phagosomes). **, p<0.01; ***, p<0.001.</p

miR-155 expression is induced after mycobacterial infection.

<p>(A) miR-155 expression levels were examined in the lungs of normal uninfected or H37Rv infected BALB/c mice 6 weeks postinfection. (B) Murine bone marrow-derived macrophages (BMDMs) were infected with BCG at an MOI of 5 for the indicated times, and the expression levels of miR-155 were measured by real-time PCR. (C and D) RAW264.7 cells were infected with BCG at an MOI of 5 for the indicated time points (C) or at indicated MOIs for 24 h (D). The expression levels of miR-155 were examined by real-time PCR. (E and F) RAW264.7 cells were infected with H37Ra at an MOI of 5 for the indicated time (E) or at indicated MOI for 24 h (F). The expression levels of miR-155 were examined by real-time PCR. Data are shown as the mean ± SEM of three independent experiments. *, p<0.05; **, p<0.01; ***, p<0.001.</p

miR-155 induces autophagy in macrophages.

<p>(A–D) RAW264.7 cells were transfected with miR-155 mimic (A and C) or inhibitor (B and D) for 24 h and then either left uninfected or infected with BCG. Expression levels of miR-155 were detected by real-time PCR (A and B). The LC3 levels were detected by Western-blot, and the ratios of LC3-II/β-actin were calculated as shown below the representative blot (C and D). (E and F) RAW264.7 cells transfected with miR-155 mimic (E) or inhibitor (F) was incubated with DMSO or bafilomycin A1 (BafA.) at a concentration of 100 nM for 2 h, and then LC3 levels were detected by Western-blot. The ratios of LC3-II/β-actin were calculated as shown below the representative blot. ***, p<0.001.</p

miR-155 promotes autophagosome formation.

<p>(A and B) RAW264.7 cells stably expressing GFP-LC3 were transiently transfected with control or miR-155 mimic for 24 h, and GFP-LC3 puncta (>1 µm) were detected by confocal microscopy (A) and quantified (B). RAW264.7 cells were transiently transfected with control or miR-155 mimic for 24 h. Endogenous LC3 was stained with LC3 antibody followed by Alexa Fluor 488-conjugated goat anti-rabbit IgG (Green), and LC3 puncta (>1 µm) were detected by confocal microscopy (C) and quantified (D). (E and F) RAW264.7 cells were transiently transfected with control or miR-155 mimic for 24 h, and then incubated with a specific fluorescent dye MDC (50 µM). The MDC-labeled autophagic vacuoles were detected by confocal microscopy (E) and cells with MDC-positive autophagic vacuoles were quantified (F). Cells treated with rapamycin were used as a positive control. Arrows indicate the GFP-LC3 puncta or autophagic vacuoles labeled with MDC; scale bar = 5 µm. Data are shown as the mean ± SEM of three independent experiments (n = 300 cells). **, p<0.01; ***, p<0.001.</p

miR-155 decreases mycobacterial survival in macrophages.

<p>(A–C) RAW264.7 cells were transfected with control or miR-155 mimic for 24 h followed by BCG (A), H37Ra (B) or H37Rv (C) infection at an MOI of 10 for 1 h, and intracellular mycobacterial viability was determined by CFU assay at the indicated timepoints. (D–F) RAW264.7 cells were transfected with control or miR-155 inhibitor for 24 h followed by BCG (D), H37Ra (E) or H37Rv (F) infection at an MOI of 10 for 1 h, and intracellular mycobacterial viability was determined by CFU assay at the indicated timepoints. (G and H) RAW264.7 cells were transfected with miR-155 mimic (G) or inhibitor (H) for 24 h followed by Texas Red-labeled BCG infection at an MOI of 10 for 1 h. Phagocytosis of mycobacteria was determined by flow cytometry. Data are shown as the mean ± SEM of three independent experiments. *, p<0.05; **, p<0.01.</p