Antisense Inhibition of the Iron-Sulphur Subunit of Succinate Dehydrogenase Enhances Photosynthesis and Growth in Tomato via an Organic Acid–Mediated Effect on Stomatal Aperture

Ilse Balbo,Adriano Nunes-Nesi,Claudia Studart-Witkowski,Alisdair R. Fernie,Xavier Jordana,Björn Usadel,Martin Lehmann,Daniela Fuentes,Fábio M. DaMatta,Enrico Martinoia,Sonia Osorio,Wagner L. Araújo,Takayuki Tohge,Réka Nagy

doi:10.1105/tpc.110.081224

Abstract

Transgenic tomato (Solanum lycopersicum) plants expressing a fragment of the Sl SDH2-2 gene encoding the iron sulfur subunit of the succinate dehydrogenase protein complex in the antisense orientation under the control of the 35S promoter exhibit an enhanced rate of photosynthesis. The rate of the tricarboxylic acid (TCA) cycle was reduced in these transformants, and there were changes in the levels of metabolites associated with the TCA cycle. Furthermore, in comparison to wild-type plants, carbon dioxide assimilation was enhanced by up to 25% in the transgenic plants under ambient conditions, and mature plants were characterized by an increased biomass. Analysis of additional photosynthetic parameters revealed that the rate of transpiration and stomatal conductance were markedly elevated in the transgenic plants. The transformants displayed a strongly enhanced assimilation rate under both ambient and suboptimal environmental conditions, as well as an elevated maximal stomatal aperture. By contrast, when the Sl SDH2-2 gene was repressed by antisense RNA in a guard cell-specific manner, changes in neither stomatal aperture nor photosynthesis were observed. The data obtained are discussed in the context of the role of TCA cycle intermediates both generally with respect to photosynthetic metabolism and specifically with respect to their role in the regulation of stomatal aperture.

Highlights

Succinate dehydrogenase (EC 1.3.5.1), often referred to as complex II, has a dual function, being important in both the tricarboxylic acid (TCA) cycle and the aerobic respiratory chain, via the catalysis of the oxidation of succinate to fumarate and the reduction of ubiquinone to ubiquinol, respectively (Hagerhall, 1997; Figueroa et al, 2001)
Comparing Sl SDH2-2 with SDH2-2 homologs from more closely related species, higher identities were observed for the related species potato (Solanum tuberosum; 98%) and tobacco (Nicotiana tabacum; 91%), while lower identities were observed for the monocots maize (69%), rice (72%), and sugarcane (Saccharum officinarum; 64%)
We identified the tomato homologs of signature genes for stomatal signal cascade from the literature as previously shown, including the small subunit of Rubisco (Rbcs), lightresponsive genes (Figure 12A), such as cation/H+ exchanger 20 (CHX20), phototropin 1 (PHOT1), PHOT2, and Cold Circadian Rhythm RNA Binding 2 (CCR2), as well as some abscisic acid (ABA)-responsive genes (Figure 12B), such as ABA insensitive 2 (ABI2), H+ ATPase (AHA2), calcium-dependent protein kinase 6 (CPK6), nitrate reductase 2 (NIA2), open stomata 1 (OST1), and phospholipase D a1 (PLDa1)

Summary

Introduction

Succinate dehydrogenase (EC 1.3.5.1), often referred to as complex II, has a dual function, being important in both the tricarboxylic acid (TCA) cycle and the aerobic respiratory chain, via the catalysis of the oxidation of succinate to fumarate and the reduction of ubiquinone to ubiquinol, respectively (Hagerhall, 1997; Figueroa et al, 2001). Complex II is the simplest of all the complexes of the electron transport chain and displays a similar composition to the closely related fumarate reductases or succinate dehydrogenases of bacteria, yeast, and mammals (Scheffler, 1998). In contrast with the situation observed in plants, complex II of nonplant systems has been the subject of somewhat greater scrutiny, with mutagenic studies being performed in Saccharomyces cerevisiae, Neurosporra crassa, Chinese hamster cells, and Caenorhabditis elegans (reviewed in Vedel et al, 1999). The study in C. elegans revealed that a mis-sense mutation in SDH cytochrome b (the 15-kD SDH3 anchoring protein) resulted in oxidative stress and premature aging in nematodes (Ishii et al, 1998). Complex II deficiency has been reported both in isolation and in combination with other genetic defects (Morris et al, 1994; Bourgeron et al, 1995; Schon, 2000; Rustin and Rotig, 2002; Rutter et al, 2010), the precise molecular bases of these deficiencies is often poorly characterized

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Conclusion