Morphophysiological alterations in transgenic rice lines expressing PPDK and ME genes from the C4 model Setaria italica

• Published in: Journal of plant physiology Vol. 264; p. 153482
• Main Authors: Swain, Alaka, Behera, Deeptirekha, Karmakar, Subhasis, Dash, Manaswini, Dash, Bisnu Prasad, Swain, Padmini, Molla, Kutubuddin A., Baig, Mirza J.
• Format: Journal Article
• Language: English
• Published: Stuttgart Elsevier GmbH 01-09-2021; Elsevier Science Ltd
• Subjects: Chlorophyll fluorescence; Electron transport; Electron transport rate; Enzymatic activity; Enzyme activity; Enzymes; Genes; Hybridization; Malate; Malic enzyme; Mesophyll; NADP; Nonphotochemical quenching; Orthophosphate; Photochemical reactions; Photochemicals; Photorespiration; Photosynthesis; Photosynthetic rate; Plant cells; Polymerase chain reaction; Pyruvate orthophosphate dikinase; Pyruvic acid; Rice; Setaria italica; Stomatal conductance; Transgenic plants; Transport rate; Water deficit; Weight; PPDK; 2,4-D; Electron transport rate; WUE; Stomatal conductance; qRT-PCR; Rubisco; Malic enzyme; NPQ; Chlorophyll fluorescence; Photosynthetic rate; NADP-ME; Pyruvate orthophosphate dikinase; Nonphotochemical quenching; RH; PPFD; qP
• ISSN: 0176-1617; 1618-1328
• DOI: 10.1016/j.jplph.2021.153482

C4 plants are superior to C3 plants in terms of productivity and limited photorespiration. PPDK (pyruvate orthophosphate dikinase) and NADP-ME (NADP-dependent malic enzyme) are two important photosynthetic C4-specific enzymes present in the mesophyll cells of C4 plants. To evaluate the effect of C4 enzymes in rice, we developed transgenic rice lines by separately introducing Setaria italica PPDK [SiPPDK] and S. italica ME [SiME] gene constructs under the control of the green tissue-specific maize PPDK promoter. Rice plant lines for both constructs were screened using the polymerase chain reaction (PCR), Southern hybridization, and expression analysis. The best transgenic plant lines for each case were selected for physiological and biochemical characterization. The results from qRT-PCR and enzyme activity analysis revealed higher expression and activity of both PPDK and NADP-ME genes compared with the nontransformed and empty-vector-transformed plants. The average photosynthetic efficiency of transgenic plant lines carrying the PPDK and NADP-ME genes increased by 18% and 12%, respectively, and was positively correlated with the increased accumulation of photosynthetic pigment. The decrease in Fv/Fm, increased electron transport rate (ETR), and increased photochemical quenching (qP) compared with nontransformed control plants suggest that transgenic rice plants transferred more absorbed light energy to photochemical reactions than wild-type plants. SiME-transgenic plants displayed reduced leaf malate content and superior performance under water deficit conditions. Interestingly, the transgenic plants showed yield enhancement by exhibiting increased plant height, panicle length, panicle weight and thousand grain weight. Overall, the exogenous foxtail millet C4 gene PPDK enhanced photosynthesis and yield to a greater extent than NADP-ME.
•We generated and evaluated transgenic rice lines, separately overexpressing PPDK and ME genes from the C4 grass, Setaria italica.•PPDK and ME enzyme activity, photosynthetic pigment content, and photosynthetic rate were enhanced in transgenic lines.•Both transgenic lines displayed superior agronomic performance to non-transgenic control.