Functional and composition differences between mitochondrial complex II in Arabidopsis and rice are correlated with the complex genetic history of the enzyme
Complex II plays a central role in mitochondrial metabolism as a component of both the electron transport chain and the tricarboxylic acid cycle. However, the composition and function of the plant enzyme has been elusive and differs from the well-characterised enzymes in mammals and bacteria. Herewith, we demonstrate that mitochondrial Complex II from Arabidopsis and rice differ significantly in several aspects: (1) Stability—Rice complex II in contrast to Arabidopsis is not stable when resolved by native electrophoresis and activity staining. (2) Composition—Arabidopsis complex II contains 8 subunits, only 7 of which have homologs in the rice genome. SDH 1 and 2 subunits display high levels of amino acid identity between two species, while the remainder of the subunits are not well conserved at a sequence level, indicating significant divergence. (3) Gene expression—the pairs of orthologous SDH1 and SDH2 subunits were universally expressed in both Arabidopsis and rice. The very divergent genes for SDH3 and SDH4 were co-expressed in both species, consistent with their functional co-ordination to form the membrane anchor. The plant-specific SDH5, 6 and 7 subunits with unknown functions appeared to be differentially expressed in both species. (4) Biochemical regulation -succinate-dependent O2 consumption and SDH activity of isolated Arabidopsis mitochondria were substantially stimulated by ATP, but a much more minor effect of ATP was observed for the rice enzyme. The ATP activation of succinate-dependent reduction of DCPIP in frozen-thawed and digitonin-solubilised mitochondrial samples, and with or without the uncoupler CCCP, indicate that the differential ATP effect on SDH is not via the protonmotive force but likely due to an allosteric effect on the plant SDH enzyme itself, in contrast to the enzyme in other organisms.
KeywordsRice Arabidopsis Mitochondria Complex II Succinate dehydrogenase
This work was supported by The Australian Research Council through the ARC Centre of Excellence in Plant Energy Biology (CE0561495) to AHM and JW, AHM is funded as an ARC Australian Professorial Fellow, NTL and HE as ARC Australian Post-doctoral Fellows. Dr. Joshua Heazlewood (Laurence Berkeley Laboratory, USA) is thanked for the gift of the mouse mitochondria. We also would like to thank an anonymous reviewer for very constructive comments.
- Elorza A, León G, Gómez I, Mouras A, Holuigue L, Araya A, Jordana X (2004) Nuclear SDH2–1 and SDH2–2 genes, encoding the iron-sulfur subunit of mitochondrial complex II in Arabidopsis, have distinct cell-specific expression patterns and promoter activities. Plant Physiol 136:4072–4087. doi: 4010.1104/pp.4104.049528 CrossRefPubMedGoogle Scholar
- Elorza A, Roschzttardtz H, Gomez I, Mouras A, Holuigue L, Araya A, Jordana X (2006) A nuclear gene for the iron-sulfur subunit of mitochondrial complex II is specially expressed during Arabidopsis seed development and germination. Plant Cell Physiol 47:14–21. doi: 10.1093/pcp/pci1218 CrossRefPubMedGoogle Scholar
- Figueroa P, Gómez I, Holuigue L, Araya A, Jordana X (1999) Transfer of rps14 from the mitochondrion to the nucleus in maize implied integration within a gene encoding the iron–sulphur subunit of succinate dehydrogenase and expression by alternative splicing. Plant J 18:601–609CrossRefPubMedGoogle Scholar
- Kubo N, Harada K, Hirai A, Kadowaki K-I (1999) A single nuclear transcript encoding mitochondrial RPS14 and SDHB of rice is processed by alternative splicing: common use of the same mitochondrial targeting signal for different proteins. Proc Natl Acad Sci USA 96:9207–9211CrossRefPubMedGoogle Scholar
- Roschzttardtz H, Fuentes I, Vasquez M, Corvalan C, Leon G, Gomez I, Araya A, Holuigue L, Vicente-Carbajosa J, Jordana X (2009) A nuclear gene encoding the iron-sulfur subunit of mitochondrial Complex II is regulated by B3 domain transcription factors during seed development in Arabidopsis. Plant Physiol 150:84–95. doi: 10.1104/pp.1109.136531 CrossRefPubMedGoogle Scholar