Abstract
Plant cells are encapsulated by cell walls whose properties largely determine cell growth. We have previously identified the rol1-2 mutant, which shows defects in seedling root and shoot development. rol1-2 is affected in the Rhamnose synthase 1 (RHM1) and shows alterations in the structures of Rhamnogalacturonan I (RG I) and RG II, two rhamnose-containing pectins. The data presented here shows that root tissue of the rol1-2 mutant fails to properly differentiate the cell wall in cell corners and accumulates excessive amounts of callose, both of which likely alter the physical properties of cells. A surr (suppressor of the rol1-2 root developmental defect) mutant was identified that alleviates the cell growth defects in rol1-2. The cell wall differentiation defect is re-established in the rol1-2 surr mutant and callose accumulation is reduced compared to rol1-2. The surr mutation is an allele of the cyclin-dependent kinase 8 (CDK8), which encodes a component of the mediator complex that influences processes central to plant growth and development. Together, the identification of the surr mutant suggests that changes in cell wall composition and turnover in the rol1-2 mutant have a significant impact on cell growth and reveals a function of CDK8 in cell wall architecture and composition.
Highlights
Growth of plants and individual cells require the coordination of numerous processes taking place in the symplast and apoplast alike
By analyzing root cell wall structures, we aimed to investigate possible changes in cell wall development due to the rol1-2 mutation
Visualization of callose in the root by aniline blue revealed significant amounts of callose in the rol1-2 mutant which was not observed in the wild type (Supplementary Figure S1)
Summary
Growth of plants and individual cells require the coordination of numerous processes taking place in the symplast and apoplast alike. A number of interactions of pectins with other cell wall components have been identified that influence the mechanical and physical properties of the cell wall. Rhamnogalacturonan I (RG I) has a backbone of α 1,4-linked Gal-Rha dimers with sidechains composed of either Ara or Gal. RG I is thought to loosely interact with other cell wall components and rather influence the porosity of the cell wall, which is a determinant of the permeability for wall-modifying enzymes. RG II, on the other hand, has a α 1,4-linked Gal backbone, has structurally complex side chains composed of a number of different sugars. It influences the mechanical properties of cell walls through ionic interactions with boron which help to crosslink RG II [4,5]
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