Plants allocate nitrogen to photosynthetic proteins to enhance nutrient capture, and supplement growth. In monocarpic species such as Arabidopsis thaliana, onset of reproductive growth induces leaf senescence. Photosynthetic proteins are degraded, and mobilized nitrogen is transported to growing tissues. The location of senescence-induced proteolysis remains ambiguous. Intact chloroplasts isolated from senescent leaves of Arabidopsis thaliana served as an experimental system to determine if proteolysis occurs in organello . The large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (LSU) is degraded during senescence, however LSU remained stable for 24 hours in senescent chloroplasts, and was abundant in chloroplasts isolated from severely senescent tissue. Glutamine Synthetase 2 (GS2) and Rubisco Activase (RCA) were rapidly degraded within 2 hours in senescent chloroplasts, and could not be detected in chloroplasts isolated from severely senescent tissue. These results indicate GS2 and RCA can be degraded in organello during leaf senescence, while LSU is degraded by an alternate mechanism.
|School:||California State University, Long Beach|
|School Location:||United States -- California|
|Source:||MAI 50/03M, Masters Abstracts International|
|Subjects:||Plant biology, Cellular biology|
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