title: The Differences between NAD-ME and NADP-ME Subtypes of C4Photosynthesis: More than Decarboxylating Enzymes.
abstract: As an adaptation to changing climatic conditions that caused high rates of photorespiration, C4plants have evolved to display higher photosynthetic efficiency than C3plants under elevated temperature, high light intensities, and drought. The C4plants independently evolved more than 60 times in 19 families of angiosperms to establish similar but not uniform C4mechanisms to concentrate CO2around the carboxylating enzyme Rubisco (ribulose bisphosphate carboxylase oxygenase). C4photosynthesis is divided into at least two basic biochemical subtypes based on the primary decarboxylating enzymes, NAD-dependent malic enzyme (NAD-ME) and NADP-dependent malic enzyme (NADP-ME). The multiple polygenetic origins of these subtypes raise questions about the association of C4variation between biochemical subtypes and diverse lineages. This review addresses the differences in evolutionary scenario, leaf anatomy, and especially C4metabolic flow, C4transporters, and cell-specific function deduced from recently reported cell-specific transcriptomic, proteomic, and metabolic analyses of NAD-ME and NADP-ME subtypes. Current omic analysis has revealed the extent to which component abundances differ between the two biochemical subtypes, leading to a better understanding of C4photosynthetic mechanisms in NAD-ME and NADP-ME subtypes.
authors: BioDiscovery Institute and Department of Biological Sciences, University of North TexasDenton, TX, USA; BioEnergy Science Center, US Department of EnergyOak Ridge, TN, USA.
authors: Xiaolan
authors: X
authors: Rao
authors: BioDiscovery Institute and Department of Biological Sciences, University of North TexasDenton, TX, USA; BioEnergy Science Center, US Department of EnergyOak Ridge, TN, USA.
authors: Richard A
authors: RA
authors: Dixon
keywords: C4 photosynthesis; C4 plants; NAD-ME subtype; NADP-ME subtype; comparative transcriptome analysis