Genetic Modification of Alternative Respiration Has Differential Effects on Antimycin A-Induced versus Salicylic Acid-Induced Resistance to Tobacco mosaic virus  

Abstract

Salicylic acid (SA), a natural defensive signal chemical, and antimycin A, a cytochrome pathway inhibitor, induce resistance to Tobacco mosaic virus (TMV). Pharmacological evidence suggested signaling during resistance induction by both chemicals involved alternative oxidase (AOX), sole component of the alternative respiratory pathway (AP). Roles of the AP include regulation of intramitochondrial reactive oxygen species and maintenance of metabolic homeostasis. Transgenic tobacco (Nicotiana tabacum) with modified AP capacities (2-to 3-fold increased or decreased) showed no alteration in phenotype with respect to basal susceptibility to TMV or the ability to display SA-induced resistance to systemic viral disease. However, in directly inoculated tissue, antimycin A-induced TMV resistance was inhibited in plants with increased AP capacities, whereas SA and antimycin A-induced resistance was transiently enhanced in plant lines with decreased AP capacities. We conclude that SA-induced TMV resistance results from activation of multiple mechanisms, a subset of which are inducible by antimycin A and influenced by AOX. Other antiviral factors, potentially including the SA-inducible RNA-dependent RNA polymerase, are regulated by AOX-independent mechanisms.

Characterization of Transformed Arabidopsis with Altered Alternative Oxidase Levels and Analysis of Effects on Reactive Oxygen Species in Tissue

“…A third round of selection on kanamycin determined homozygous individuals (T 3 ) and these and their progeny (T 4 ) were used for further characterization. During the selection process, no morphological or fertility phenotypic differences were observed for any of the transformants, similar to other cases of transformation with AOX under CaMV 35S promoter control (Vanlerberghe et al, 1994;Millenaar, 2000;Gilliland et al, 2003).…”

“…However, a striking decrease in pollen viability occurred when an AOX anti-sense construct was used with a tapetum-specific promoter in tobacco (Kitashiba et al, 1999). Only two studies have examined the effects of changes in AOX content on whole plants, both with respect to TMV resistance (Ordog et al, 2002;Gilliland et al, 2003). The tobacco CaMV 35S transformants have been used almost exclusively as suspension culture cells (Vanlerberghe et al, 1997;Parsons et al, 1999;Robson and Vanlerberghe, 2002), including the work examining ROS generation (Maxwell et al, 1999).…”

“…Plants with altered AOX levels have been produced for potato (Solanum tuberosum; Hiser et al, 1996) and tobacco (Vanlerberghe et al, 1994(Vanlerberghe et al, , 1998Millenaar, 2000;Gilliland et al, 2003) using the cauliflower mosaic virus (CaMV) 35S promoter and, for Arabidopsis (Arabidopsis thaliana), using a copper-inducible promoter (Potter et al, 2001). Limited characterization of detached leaves from these transformants has been reported (Vanlerberghe et al, 1995;Potter et al, 2001) and no growth phenotypes were noted.…”

Overexpression of wheat alternative oxidase gene Waox1a alters respiration capacity and response to reactive oxygen species under low temperature in transgenic Arabidopsis

“…Western blot analysis was performed using a mitochondria-enriched fraction prepared from seedlings grown under the standard condition and monoclonal antibody against AOX (Elthon et al 1989). No morphological alterations were observed during selection process of the transgenic plants, which agreed with the previous reports of transformation with the tobacco and Arabidopsis AOX genes (Gilliland et al, 2003;Umbach et al, 2005). Total RNA samples for expression analysis were extracted from the Arabidopsis seedling leaves and treated with DNaseI to remove the contaminated DNA.…”

The Road to RNA Silencing is Paved with Plant-Virus Interactions

“…Some of these RdRps are now known to be involved not only in RNA silencing, but also in transcriptional silencing of DNAs and the epigenetic control of gene expression (Chan et al, 2004;Lippman and Martienssen, 2004;Wassenegger, 2005). RdRps are also involved in innate resistance, including the salicylic acidmediated defense response (Gilliland et al, 2003;Xie et al, 2001;Yang et al, 2004) and the jasmonic acid-mediated defense response (Pandey and Baldwin, 2007;Pandey et al, 2008). Thus, the RdRps are key components of quite different defense pathways, providing defenses against viruses, bacteria, fungi and insects (Boller and Felix, 2009;Carr et al, 2010;Chisholm et al, 2006).…”