Fig. 4. Overexpression of CgMYB58 increased lignin accumulation and promoted the expression of lignin biosynthetic genes in citrus calli.

a CgMYB58 transiently expressed in pummelo mesocarp. HR fruit mesocarp were injected with Agrobacteria containing an empty vector (I, II) or a CgMYB58 overexpression vector (III, IV) and imaged under bright-field (I, III) and GFP fluorescence conditions (II, IV). GFP fluorescence indicated that the vectors were successfully transferred into the pummelo fruit mesocarp. b Lignin contents were measured in pummelo fruit mesocarp tissue after transient transformation with an empty vector (EV) or a CgMYB58 overexpression vector. c Relative expression levels of CgMYB58 in WT-RM (Red Marsh) and eight transgenic RM calli lines overexpressing CgMYB58. d Lignin content in the calli of WT and eight transgenic lines. The asterisks indicate significant differences relative to WT-RM according to a t-test (***P < 0.05). e Phenotypes WT-RM calli and the two transgenic lines stained with phloroglucinol-HCl. The WT-RM calli did not show any staining, whereas the calli of the two transgenic RM lines (CgMYB58-OE04, -OE11) were stained red. f Cluster heatmap based on the transcript level of lignin biosynthetic genes. Among the 30 examined lignin biosynthetic genes, 19 were upregulated in the CgMYB58-OE lines, which are highlighted in red