Senescence-associated vacuoles with intense proteolytic activity develop in leaves of Arabidopsis and soybean

Vacuolar compartments associated with leaf senescence and the subcellular localization of the senescence-specific cysteine-protease SAG12 (senescence-associated gene 12) were studied using specific fluorescent markers, the expression of reporter genes, and the analysis of high-pressure frozen/freeze...

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Bibliographic Details
Published in:The Plant journal : for cell and molecular biology 2005-03, Vol.41 (6), p.831-844
Main Authors: Otegui, M.S, Noh, Y.S, Martinez, D.E, Petroff, M.G.V, Staehelin, L.A, Amasino, R.M, Guiamet, J.J
Format: Article
Language:English
Subjects:
Arabidopsis
Arabidopsis - enzymology
Arabidopsis - genetics
Arabidopsis - ultrastructure
Arabidopsis Proteins - physiology
Arabidopsis thaliana
Biological and medical sciences
Botany
cellular breakdown
Chloroplasts
Cysteine Endopeptidases - physiology
cysteine proteinases
Flowers & plants
Fundamental and applied biological sciences. Psychology
Glycine max
Glycine max - enzymology
Glycine max - genetics
Glycine max - ultrastructure
guard cells
Hydrogen-Ion Concentration
Leaves
mesophyll
molecular sequence data
Mutation
nucleotide sequences
phenotypic variation
Plant Leaves - enzymology
Plant Leaves - ultrastructure
Plant physiology and development
plant proteins
Plants, Genetically Modified
Proteases
proteolysis
SAG12
senescence
Senescence and abscission
senescence-associated gene
senescence-associated vacuoles
senescence‐associated protease
Soybeans
Time Factors
tissue distribution
transgenes
transgenic plants
vacuoles
Vacuoles - chemistry
Vacuoles - enzymology
Vegetative apparatus, growth and morphogenesis. Senescence
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Summary:Vacuolar compartments associated with leaf senescence and the subcellular localization of the senescence-specific cysteine-protease SAG12 (senescence-associated gene 12) were studied using specific fluorescent markers, the expression of reporter genes, and the analysis of high-pressure frozen/freeze-substituted samples. Senescence-associated vacuoles (SAVs) with intense proteolytic activity develop in the peripheral cytoplasm of mesophyll and guard cells in Arabidopsis and soybean. The vacuolar identity of these compartments was confirmed by immunolabeling with specific antibody markers. SAVs and the central vacuole differ in their acidity and tonoplast composition: SAVs are more acidic than the central vacuole and, whereas the tonoplast of central vacuoles is highly enriched in gamma-TIP (tonoplast intrinsic protein), the tonoplast of SAVs lacks this aquaporin. The expression of a SAG12-GFP fusion protein in transgenic Arabidopsis plants shows that SAG12 localizes to SAVs. The analysis of Pro(SAG12):GUS transgenic plants indicates that SAG12 expression in senescing leaves is restricted to SAV-containing cells, for example, mesophyll and guard cells. A homozygous sag12 Arabidopsis mutant develops SAVs and does not show any visually detectable phenotypical alteration during senescence, indicating that SAG12 is not required either for SAV formation or for progression of visual symptoms of senescence. The presence of two types of vacuoles in senescing leaves could provide different lytic compartments for the dismantling of specific cellular components. The possible origin and functions of SAVs during leaf senescence are discussed.
ISSN:0960-7412
1365-313X
DOI:10.1111/j.1365-313X.2005.02346.x