add Supplementary Figure 4 caption

assays/qPCR/README.md

@@ -8,4 +8,18 @@ Suppl. Table 2.
 
 ### Supplementary Figure 3 source
 
+https://www.frontiersin.org/articles/10.3389/fpls.2023.1024981/full#supplementary-material
+
+### Supplementary Figure 4 caption
+
+**Supplementary Figure 4:** Results of qRT-PCR for genes sqs and dxs as log10-fold changes
+compared to the control strain in the strains *Synechocystis* Δshc pEERM Prha sqs pSHDY rhaS,
+*Synechocystis* Δshc pEERM Prha dxs pSHDY rhaS, respectively. Values were calculated via the
+2−ΔΔCT method, using rpoA as a housekeeping gene and cDNA extracted from *Synechocystis* Δshc
+pSHDY rhaS, treated with the same rhamnose concentration as a control strain. Primer sequences are
+shown in Suppl. Table 2. The mean and standard deviation of two biological replicates is shown,
+which were measured in technical triplicates.
+
+### Supplementary Figure 4 source
+
 https://www.frontiersin.org/articles/10.3389/fpls.2023.1024981/full#supplementary-material
\ No newline at end of file