The authors contributed equally to this work.
A subtilisin-like serine protease essential for mucilage release from Arabidopsis seed coats
Article first published online: 7 FEB 2008
© 2008 University of Potsdam Journal compilation © 2008 Blackwell Publishing Ltd
The Plant Journal
Volume 54, Issue 3, pages 466–480, May 2008
How to Cite
Rautengarten, C., Usadel, B., Neumetzler, L., Hartmann, J., Büssis, D. and Altmann, T. (2008), A subtilisin-like serine protease essential for mucilage release from Arabidopsis seed coats. The Plant Journal, 54: 466–480. doi: 10.1111/j.1365-313X.2008.03437.x
- Issue published online: 7 FEB 2008
- Article first published online: 7 FEB 2008
- Received 16 December 2007; revised 15 January 2008; accepted 23 January 2008.
- cell wall;
- seed coat;
- pectin methylesterase;
- Arabidopsis thaliana
During Arabidopsis seed development large quantities of mucilage, composed of pectins, are deposited into the apoplast underneath the outer wall of the seed coat. Upon imbibition of mature seeds, the stored mucilage expands through hydration and breaks the outer cell wall that encapsulates the whole seed. Mutant seeds carrying loss-of-function alleles of AtSBT1.7 that encodes one of 56 Arabidopsis thaliana subtilisin-like serine proteases (subtilases) do not release mucilage upon hydration. Microscopic analysis of the mutant seed coat revealed no visible structural differences compared with wild-type seeds. Weakening of the outer primary wall using cation chelators triggered mucilage release from the seed coats of mutants. However, in contrast to mature wild-type seeds, the mutant’s outer cell walls did not rupture at the radial walls of the seed coat epidermal cells, but instead opened at the chalazal end of the seed, and were released in one piece. In atsbt1.7, the total rhamnose and galacturonic acid contents, representing the backbone of mucilage, remained unchanged compared with wild-type seeds. Thus, extrusion and solubility, but not the initial deposition of mucilage, are affected in atsbt1.7 mutants. AtSBT1.7 is localized in the developing seed coat, indicating a role in testa development or maturation. The altered mode of rupture of the outer seed coat wall and mucilage release indicate that AtSBT1.7 triggers the accumulation, and/or activation, of cell wall modifying enzymes necessary either for the loosening of the outer primary cell wall, or to facilitate swelling of the mucilage, as indicated by elevated pectin methylesterase activity in developing atsbt1.7 mutant seeds.