†Present address: Kumho Life & Environmental Science Laboratory, 1 Oryong-Dong, Puk-Gu, Kwangju 500-712, South Korea.
Senescence-associated vacuoles with intense proteolytic activity develop in leaves of Arabidopsis and soybean
Article first published online: 26 JAN 2005
The Plant Journal
Volume 41, Issue 6, pages 831–844, March 2005
How to Cite
Otegui, M. S., Noh, Y.-S., Martínez, D. E., Vila Petroff, M. G., Andrew Staehelin, L., Amasino, R. M. and Guiamet, J. J. (2005), Senescence-associated vacuoles with intense proteolytic activity develop in leaves of Arabidopsis and soybean. The Plant Journal, 41: 831–844. doi: 10.1111/j.1365-313X.2005.02346.x
- Issue published online: 26 JAN 2005
- Article first published online: 26 JAN 2005
- Received 13 September 2004; revised 6 December 2004; accepted 10 December 2004.
- cellular breakdown;
- senescence-associated protease;
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 γ-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 ProSAG12: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.