Fig. 3: The special photosynthetic system in Mikania micrantha.

a The number of putative carbon fixation genes in M. micrantha, pineapple and sunflower. The gene number of pineapple was obtained from the literature²⁸; carbonic anhydrase (CA), phosphoenolpyruvate carboxylase (PEPC), phosphoenolpyruvate carboxykinase (PEPCK), malic enzyme (ME), malate dehydrogenase (MDH), and pyruvate orthophosphate dikinase (PPDK). b Expression pattern of CAM pathway key genes in M. micrantha across the diurnal expression data. The R-package (pheatmap)-transformed transcripts per kilobase million (TMP) expression profiles are shown. The gene names of M. micrantha are shown on the right. The gene expression of each replicate sample in two time points (9 A.M. and 9 P.M.) presented in the heatmap. c The diurnal variation pattern of key enzyme activities and malic acid content in M. micrantha leaves at 9:00 A.M. (day) and 9:00 P.M. (night). The y-axis on the left shows the activity of PEPC and NADP-linked ME. Statistical significance (n = 3) determined using the two-sided Student’s t test. On each box plot, the central mark indicates the median, the bottom and top edges of the box indicate the interquartile range (IQR) and the whiskers represent the maximum and minimum data points. d Scanning electron microscopy (SEM) of stomata in M. micrantha leaves during the day and at night. SEM images of the samples were taken using a scanning electron microscope (Q25, FEI, USA). e Schematic of the CAM and C₃ photosynthesis proposed pathways of M. micrantha. The enzymes in the CAM pathway of M. micrantha are shown in red. During the day, carbon dioxide is absorbed directly by the leaves through the C₃ pathway. At night, carbon dioxide is fixed nocturnally by PEPC and stored transiently as malic acid in large vacuoles. Furthermore, carbon dioxide is released from organic acids through NADP-linked ME and used directly in the Calvin cycle in the daytime. The source data underlying Fig. 3b–d are provided as a Source Data file.