The function of ascorbate oxidase in tobacco

Area of Science:

• Plant Physiology
• Biochemistry
• Molecular Biology

Background:

• Ascorbate oxidase (AO) is an apoplastic enzyme involved in plant growth and development.
• Light and hormones significantly influence plant metabolic pathways and gene expression.

Purpose of the Study:

• To investigate the function of apoplastic ascorbate oxidase (AO) in tobacco (Nicotiana tabacum).
• To determine the impact of altered AO expression on ascorbate levels, plant growth, and responses to light and hormones.

Main Methods:

• Investigated AO mRNA abundance under different light conditions and hormonal treatments (salicylic acid, auxin).
• Generated transgenic tobacco plants with sense and antisense AO expression to manipulate apoplastic AO activity.
• Assessed whole leaf and apoplastic ascorbate (AA) content, plant height, and biomass in transformed plants.

Main Results:

• AO mRNA levels were up-regulated by light and auxin, and down-regulated by salicylic acid, correlating with growth changes.
• Altered apoplastic AO activity dramatically affected apoplastic AA levels but had minimal impact on whole leaf AA content.
• Modified AO expression altered the relationship between AO activity and plant height/biomass, and abolished light/dark regulation of native AO transcripts.

Conclusions:

• Apoplastic AO activity plays a crucial role in regulating ascorbate redox state and influences plant growth and biomass.
• AO expression integrates signals from light, hormones, and redox status in the apoplast.
• Modulating AO activity offers a potential strategy to influence plant development through redox homeostasis.