ISSN 1607-6729, Doklady Biochemistry and Biophysics, 2011, Vol. 440, pp. 207–210. © Pleiades Publishing, Ltd., 2011. Original Russian Text © N.S. Belozerova, E.S. Pojidaeva, A.G. Shugaev, V.V. Kuznetsov, 2011, published in Doklady Akademii Nauk, 2011, Vol. 440, No. 2, pp. 266–269. 207 The mitochondrial genome of plants is larger than that of animals and fungi and may consist of 180 to 2500 kb. The set of mitochondrial genes of plants does not differ significantly from other eukaryotes; how- ever, plant genome is less compact because of the pres- ence of long noncoding regions separating the coding sequences. In the completely sequenced mitochon- drial genome of A. thaliana, 57 genes were identified and 85 open reading frames of unknown function were distinguished, some of which may encode proteins that are specific only for plants [1]. In particular, depending on plant species, the mitochondrial genome encodes three ribosomal RNAs, an average of 16 transfer RNAs, about ten ribosomal proteins, some proteins of the respiratory chain, some of ATP syn- thase subunits, and four proteins involved in the syn- thesis of cytochrome с. Despite the small information capacity of the mitochondrial genome, its functioning is essential for plant growth and development. In the past 20 years, it was demonstrated that mutations in the mitochondrial genome result in numerous serious diseases of humans and animals [2]. Although the genetic control of biogenesis and metabolism of mito- chondria, including plant mitochondria, is exercised primarily by nuclear genes, the organelles themselves can also have a certain regulatory effect on these pro- cesses, for example, by the retrograde regulation mechanism [3]. Although there is no doubt that a sig- nal that coordinates the functioning of the two genomes indeed exists, its nature in plants remains unknown. It was assumed that, in animals, com- pounds with hormonal activity have a major role in this process [4]. Among the phytohormones, salicylic acid (SA) has the greatest influence on mitochondrial metabolism. Salicylic acid, as a phytohormone of phenolic nature, has a wide range of physiological effects and induces the expression of several genes encoding the proteins (including mitochondrial ones) that increase the resis- tance of plants to biotic and abiotic stressors. In par- ticular, we showed that endogenous and exogenous SA induces the expression of nuclear genes encoding the alternative oxidase (AO) of the electron-transport chain (ETC) of mitochondria and dramatically increases the activity of uncoupled cyanide-resistant respiration in thermogenic and nonthermogenic tis- sues of plants [5]. It was postulated that the existence of alternative routes of electron transport, which, in addition to AO, include the rotenone-insensitive NAD(P)H dehydrogenases shuttling the first stage of energy coupling (complex I), imparts greater flexibil- ity to functioning ETC, and facilitates adaptation of plants to adverse environmental conditions [6]. The influence of SA and other phytohormones on the expression of the mitochondrial genome, includ- ing the expression of genes encoding the subunits of ETC complexes, has so far remained obscure. How- ever, the existence of such an effect seems quite likely, especially given that the functioning of the mitochon- drial ETC is regulated by both nuclear and mitochon- drial genomes. It is known that the alternative pathway is determined by the activity of one enzyme, AO, which consists of two identical subunits encoded by nuclear genes, whereas the complexes of the main route of electron transfer consist of many polypeptides encoded by both nuclear and mitochondrial genes. Both electron transfer routes are closely related, and a change in the activity of one entails a change in the functioning of the other. Salicylic acid, along with other signaling molecules, apparently plays major role in this interaction [3]. The goal of this study was to determine whether SA is involved in the regulation of expression of mito- chondrial genes. For this purpose we used run-on transcription, which, unlike the most commonly used methods (Northern hybridization and polymerase chain reaction (PCR)), after performing reverse tran- scription allows studying the effect of endogenous and Salicylic Acid Differently Regulates the Transcription Intensity of the Mitochondrial Genes of Lupinus luteus L. N. S. Belozerova, E. S. Pojidaeva, A. G. Shugaev, and V. V. Kuznetsov Presented by Academician A.I. Miroshnikov April 25, 2011 Received April 28, 2011 DOI: 10.1134/S1607672911050036 Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, ul. Botanicheskaya 35, Moscow, 127276 Russia BIOCHEMISTRY, BIOPHYSICS AND MOLECULAR BIOLOGY