Photosynthetic performance and fertility are repressed in GmAOX2b antisense soybean.

Tsun-Thai Chai,David A Day,Timothy D Colmer,Patrick M Finnegan,Daina Simmonds

doi:10.1104/pp.109.149294

Abstract

The alternative oxidase (AOX) is a cyanide-resistant oxidase that provides an alternative outlet for electrons from the respiratory electron transport chain embedded in the inner membrane of plant mitochondria. Examination of soybean (Glycine max) plants carrying a GmAOX2b antisense gene showed AOX to have a central role in reproductive development and fecundity. In three independently transformed antisense lines, seed set was reduced by 16% to 43%, whereas ovule abortion increased by 1.2- to 1.7-fold when compared with nontransgenic transformation control plants. Reduced fecundity was associated with reductions in whole leaf cyanide-resistant, salicylhydroxamic acid-sensitive respiration and net photosynthesis, but there was no change in total respiration in the dark. The frequency of potential fertilization events was reduced by at least one-third in the antisense plants as a likely consequence of prefertilization defects. Pistils of the antisense plants contained a higher proportion of immature-sized, nonfertile embryo sacs compared with nontransgenic control plants. Increased rates of pollen abortion in vivo and reduced rates of pollen germination in vitro suggested that the antisense gene compromised pollen development and function. Reciprocal crosses between antisense and nontransgenic plants revealed that pollen produced by antisense plants was less active in fertilization. Taken together, the results presented here indicate that AOX expression has an important role in determining normal gametophyte development and function.

Highlights

The alternative oxidase (AOX) is a cyanide-resistant oxidase that provides an alternative outlet for electrons from the respiratory electron transport chain embedded in the inner membrane of plant mitochondria
Three independent soybean transgenic events were recovered after the introduction of a full-length GmAOX2b cDNA in the AS orientation under the control of the 35S promoter
The defective pollen and ovule phenotypes in GmAOX2b AS soybean demonstrated that AOX expression is important to gametophytic development and function

Summary

Introduction

The alternative oxidase (AOX) is a cyanide-resistant oxidase that provides an alternative outlet for electrons from the respiratory electron transport chain embedded in the inner membrane of plant mitochondria. Increased rates of pollen abortion in vivo and reduced rates of pollen germination in vitro suggested that the antisense gene compromised pollen development and function. The electron transport system embedded in the plant inner mitochondrial membrane contains two terminal oxidases, cytochrome oxidase and alternative oxidase (AOX). A major role for AOX in plants appears to be in the avoidance of oxidative stress by maintaining a low level of reduction of the ubiquinone pool of the respiratory chain (Maxwell et al, 1999), and AOX gene expression is induced strongly by most stress conditions (Clifton et al, 2005).

Methods

Results

Conclusion