A virescent plastid mutation in tobacco decreases peroxisome enzyme activities in seedlings

Chloroplasts engage in a number of activities, such as photorespiration, which closely involve other organelles in the cell. How these activities are regulated and coordinated is poorly understood although numerous studies have shown that chloroplasts exert some control over the expression of proteins that function in other organelles. We asked if intra-organellar interactions of this type could be involved in the phenotype of the Vir-e chloroplast mutation in tobacco. This maternally-inherited mutation retards seedling development, including both heterotrophic and photosynthetic stages. Since glyoxysomes are critical while seedling are still heterotrophic, and peroxisomes are critical once they become photoautotrophic, we reasoned that the Vir-c mutation might act in part by influencing enzymes that function in these organelles. We analyzed glyoxysome and peroxisome-specific functions and enzyme activities in Vir-c mutant seedlings and compared them to wildtype tobacco. We found that glyoxysome functions in Vir-e seedlings are normal. The peroxisome-specific enzymes catalase and glycolate oxidase, however, showed much lower levels of activity in Vir-c seedlings.