Poster: Organelle Biogenesis
Abs #
1169: A novel class of lytic vacuoles associated with leaf senescence in Arabidopsis and soybean
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Presenter: |
Otegui, Marisa S, marisa_ote@yahoo.com | Authors | Otegui, Marisa S (A) Noh, Yoo S (B) (C) Martinez, Dana E (A) Amasino, Richard M (B) Guiamet, Juan J (A) | | Affiliations: |
(A): Inst. de Fisiología Vegetal, CONICET-UNLP, cc 327 1900-La Plata, Argentina
(B): Dept. of Biochemistry, Univ. of Wisconsin, 433 Babcock Dr., Madison, WI 53706-1544, USA
(C): Kumho Life and Environmental Science Laboratory, 1 Oryong-dong, Puk-gu, Kwangju 500-712, South Korea
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Senescence is characterized by massive degradation of proteins, lipids, and nucleic acids. Lytic vacuoles contain a wide range of hydrolases (e.g., proteases, nucleases, esterases, etc) that are probably involved in the degradation of cellular components. The up-regulation of vacuolar proteases and of vacuolar processing enzymes during senescence suggests that vacuoles might play a role in the senescence-associated degradation of macromolecules.
With the improved structural preservation achieved by using high-pressure freezing/freeze-substitution fixation of specimens for electron microscopy, we have detected a distinct population of small vacuoles (~1 micron in diameter) that are virtually absent in young leaves but increase in abundance during senescence in Arabidopsis and soybean. Similar senescence-associated vacuoles, of the same size, can be visualized in vivo by confocal microscopy with the aid of fluorochromes that specifically label vacuolar (acidic) compartments, i.e, neutral red and Lysotracker Red. In vivo staining with rhodamine 110, bis-(CBZ-L-phenylalanyl-L-arginine amide), a substrate for thiol proteases, shows that a large part of the thiol protease activity of senescing cells is located in these vacuoles. A fusion protein between GFP and SAG12, a strictly senescence-specific thiol protease, is targeted to the same senescence-associated vacuoles. We conclude that these are a novel class of lytic vacuoles that may play an important role in cellular disassembly during senescence.
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