Light‐dependent gene expression for proteins in the respiratory chain of potato leaves

Abstract

SummaryExpression of genes for respiratory chain dehydrogenases was investigated in potato (Solanum tuberosum L. cv. Desiree) leaves. The recently characterized nda1 and ndb1 genes, homologues to genes encoding the non-proton pumping respiratory chain NADH-dehydrogenases of Escherichia coli and yeast, were compared to genes encoding catalytic subunits of the proton-pumping NADH dehydrogenase (complex I). As leaves develop from young to mature, the nda1 transcript level increases, accompanied by an elevation in immunodetected NDA protein and internal rotenone-insensitive NADH oxidation. The other investigated transcripts, proteins and NAD(P)H oxidation activities were essentially unchanged. A variation in transcript level, speci®c for nda1, is seen at different times of the day with highest expression in the morning. This variation also in¯uences the apparent developmental induction. Further, the nda1 mRNA in leaves speci®cally and completely disappears during dark treatment, with a rapid reinduction when plants are returned to light. Corresponding immunodetected NDA protein is speci®cally decreased in mitochondria isolated from dark-treated plants, accompanied by a lower capacity for internal rotenone-insensitive NADH oxidation. Complete light dependence and diurnal changes in expression have previously not been reported for genes encoding respiratory chain proteins. Qualitatively similar to NDA, the alternative oxidase showed developmental induction and light dependence. In addition to the speci®c change in nda1, a general, slower down-regulation in darkness was seen for the other NAD(P)H dehydrogenase genes. The nda1 expression during development, and in response to light, indicates a speci®c role of the encoded enzyme in the photosynthetically associated mitochondrial metabolism.

Light Regulation of the Arabidopsis Respiratory Chain. Multiple Discrete Photoreceptor Responses Contribute to Induction of Type II NAD(P)H Dehydrogenase Genes

“…A rapid real-time PCR assay was used to screen for relative alterations in transcript abundance in 5-d-old etiolated Arabidopsis seedlings maintained in continuous darkness or exposed to 10 mmol m 22 s 21 white light for 4 or 12 h (Table I). The nonlight-responsive gene encoding the 76-kD subunit of ETC complex I was used as a negative internal control (Svensson and Rasmusson, 2001) and the lightinduced gene encoding Gly decarboxylase subunit H (gdcH) was used as a positive control (Srinivasan and Oliver, 1995;Tepperman et al, 2004).…”

“…In addition, these enzymes are likely involved in balancing cellular redox and energy status (van Lis and Atteia, 2004) and in minimizing the production of reactive oxygen species (ROS) generated by overreduction of basal respiratory chain components (Purvis and Shewfelt, 1993;Maxwell et al, 1999;Møller, 2001;Svensson et al, 2002;Brandalise et al, 2003). Interestingly, the expression of several genes encoding energy-dissipating respiratory proteins is tightly regulated by various environmental stimuli (Finnegan et al, 1997;Laloi et al, 1997;Svensson and Rasmusson, 2001;Svensson et al, 2002), which contrasts with the more constitutive expression of studied basal ETC components (with some exceptions; see e.g. Hilton and Owen, 1985).…”

“…Thus, dynamic alterations in the ETC, most likely the structurally simple energy-dissipating proteins, may be necessary to accommodate increased electron flux in the light without substantially increasing ROS production. Indeed, it has recently been demonstrated that the type II NAD(P)H dehydrogenase gene nda1 is regulated by light in potato (Solanum tuberosum) and Arabidopsis (Svensson and Rasmusson, 2001;Michalecka et al, 2003) and that the alternative oxidase gene aox2a is light induced in soybean (Glycine max; Finnegan et al, 1997). The mode of signaling underlying light-regulated changes in mitochondria has not been investigated, but van Lis and Atteia (2004) have suggested a primary role for redox regulation.…”

Identification of AtNDI1, an Internal Non-Phosphorylating NAD(P)H Dehydrogenase in Arabidopsis Mitochondria

“…That is, it is possible that there is a level of redundancy in the genome and that these genes are interchangeable, the two genes perhaps being induced under different conditions or in different tissues. For example, in potato, the internal NAD(P)H DH (NDA) is thought to be cold and light inducible in leaves (Rasmusson et al, 1999;Svensson and Rasmusson, 2001;Svensson et al, 2002). Future work to characterize all of the enzymes involved in the oxidation of matrix NAD(P)H could include the analysis of a double mutant.…”

“…Both were found using a single Arabidopsis expressed sequence tag to probe a cDNA library, indicating a significant level of homology between the different gene sequences. The physiological functions and different regulatory mechanisms of these enzymes are not fully understood, although induction under light stress and repression of matrix NAD(P)H DH expression under cold stress has been reported (Svensson and Rasmusson, 2001;Svensson et al, 2002).…”