Transcriptomic insights of photosynthetic efficiency in Gymnema sylvestre(Retz.) R.Br. Kalariya Kuldeepsingh A.* ICAR-Directorate of Medicinal and Aromatic Plants Research, Boriavi, Anand-387310, Gujarat, India *E-mail: kuldeep.kalariya@icar.gov.in
Online Published on 06 January, 2022. Abstract Gymnema sylvestre is a slow growing, important non-model plant with immense medicinal value. Stomatal characteristics, gaseous exchange, chlorophyll fluorescence parameters and transcriptome were studied in two genotypes i.e. DGS 3 and DGS 22. There was no variation in stomatal density and stomatal index among these genotypes. Chlorophyll a, b and carotenoids content were higher in DGS 22 as compared to the DGS 3. However, the photosynthetic light curve study revealed that net photosynthetic rate (PN) was higher in DGS 3 during exposure between 250 and 2000 μmol photon m−2 s−1 photosynthetic active light (PAR). Stomatal limitation (Ls) was higher in DGS 3 as compared to the DGS 22 between 750 and 1500 PAR. The maximum efficiency of photosynthesis (Fv/Fm) was similar in both genotypes however, the actual efficiency of photosynthesis (F'v/F'm) and the quantum yield of PS II (ΦPSII) were higher in DGS 3. Through transcriptome analysis, five main pathways related to the photosynthesis were investigated and 123 genes were identified. The pathway leading to the biosynthesis of porphyrin and chlorophyll metabolism had 30 genes with 68% of the genes up regulated in DGS 22. Carotenoid biosynthesis [ko00906] was characterized by a total of 18 genes with 80% of the genes upregulated in DGS 22. Even though having similar Fv/Fm, higher chlorophylls and carotenoids content, major reason behind low PN was down regulation of Rubisco small subunit (rbcS) whereas an efficient xanthophyll cycle helped better protect photosystem II (PS II) through maintaining high non-photochemical quenching (NPQ) in DGS 22. Top Keywords Chlorophyll fluorescence, Gymnema sylvestre, Maximum efficiency of photosynthesis, Ribulose-1, 5-bisphosphate carboxylase/oxygenase, Stomatal conductance, Transcriptome analysis. Top |