The multiple alternative oxidase proteins of soybean

Abstract

The identity of the multiple alternative oxidase bands detected in various soybean tissues was investigated to determine if any modification that can alter the mobility on SDS-PAGE of the alternative oxidase occurs after mitochondrial import other than removal of the presequence. Comparison of the mature, in vitro imported products of AOX1, AOX2 and AOX3 in soybean cotyledons and rat liver mitochondria indicated that they had an identical apparent molecular mass to their in vitro expressed mature forms. This suggests that no modification specific to plant alternative oxidase altering the mobility on SDS-PAGE, took place. Changing the –2 and/or –3 Arg residue resulted in the inhibition of the generation of this mature form, suggesting that processing was most likely by the general mitochondrial processing peptidase. Comparison of the in vitro expressed mature forms to that detected by immunoblots of soybean tissues, required the induction of AOX1. Treatment of soybean cultured cells with antimycin A resulted in the induction of an additional band cross-reacting to monoclonal antibodies against the alternative oxidase. Comparison of the in vitro expressed mature forms to the alternative oxidase detected by western blotting indicated that they were identical in apparent molecular mass. These results indicated that no modification other than presequence removal, which alters mobility on SDS-PAGE, was required to generate the mature functional alternative oxidase proteins.

Regulation of the Alternative Oxidase Aox1 Gene inChlamydomonas reinhardtii. Role of the Nitrogen Source on the Expression of a Reporter Gene under the Control of theAox1 Promoter

“…It has also to be pointed out that AOX isoforms unresponsive to cytochrome pathway inhibition and chemical induction have been described in several organisms (Saisho et al, 1997;Tanudji et al, 1999;Huh and Kang, 2001). In eudicot plant species in particular, the AOX is encoded in two discrete gene subfamilies: The Aox1 subfamily is responsive to stress agents and respiratory inhibitors, whereas the Aox2 subfamily shows tissue and developmental stage specificity but does not respond to Aox1-inducing agents (Considine et al, 2002).…”

“…Some of these conditions include saline (Hilal et al, 1998) and oxidative stresses (Wagner, 1995;Vanlerberghe and McIntosh, 1996), exposure to heavy metals (Padua et al, 1999), inhibition of mitochondrial protein synthesis (Zhang et al, 1996), cytochrome pathway restriction McIntosh, 1992, 1994;Saisho et al, 1997;Wagner and Wagner, 1997;Tanudji et al, 1999;Ducos et al, 2001), and incubation with metabolites such as acetate, Cys, or salicylic and citric acids (Elthon et al, 1989;Rhoads and McIntosh, 1992;Vanlerberghe and McIntosh, 1996;Lennon et al, 1997;Potter et al, 2000). In fungi, AOX induction is especially dependent on cytochrome pathway restriction (Lambowitz et al, 1989;Sakajo et al, 1991;Minagawa et al, 1992;Li et al, 1996;Yukioka et al, 1998;Huh andKang, 1999, 2001) and triggering by reactive oxygen species (Yukioka et al, 1998;Huh and Kang, 2001).…”

Molecular Distinction between Alternative Oxidase from Monocots and Dicots

“…Note: "Aox0" does not preclude multiple Aox-immunoreactive bands in the study referenced. Finnegan et al (1997Finnegan et al ( , 1999McCabe et al (1998);Tanudji et al (1998Tanudji et al ( , 1999; Djajanegara (2000) Vanlerberghe and McIntosh (1992a, 1992b …”

“…In soybean, Aox1 expression has only been documented after respiratory inhibition of cell cultures by antimycin A Tanudji et al, 1999). The two soybean Aox2-type isozymes, Aox2 and Aox3 (now renamed Aox2a and Aox2b), are more prevalent, although differentially regulated McCabe et al, 1998).…”

“…Studies have revealed differential expression of the soybean genes in response to developmental cues and environmental perturbations McCabe et al, 1998;Tanudji et al, 1999). In soybean, Aox1 expression has only been documented after respiratory inhibition of cell cultures by antimycin A Tanudji et al, 1999).…”