Mutations in Cellulose Synthase (CESA1) Phosphorylation Sites Affect Cell Expansion and Cellulose Synthesis

Strategic Insights -

Researchers at the University of California, BioSciences Institute, have found that mutations in the phosphorylation sites of the CESA1 component of cellulose synthase significantly impact anisotropic cell expansion and bidirectional mobility of cellulose synthase. The study, published in the Proceedings of the National Academy of Sciences, reveals that these mutations can alter the structure of cellulose microfibrils in the primary cell wall, leading to defects in cell expansion. The researchers also discovered that the rate of movement of cellulose synthase complexes is directionally asymmetric in mutant lines with abnormal cell expansion.

Key Takeaways:

  • Mutations in the phosphorylated residues of CESA1 alter anisotropic cell expansion and cellulose synthesis in rapidly expanding roots and hypocotyls.
  • Expression of T166E, S686E, or S688E mutants of CESA1 fully rescued the temperature-sensitive cesA1-1 allele (rsw1) at a restrictive temperature.
  • Mutations to E at residues surrounding T166 caused opposite effects, including defective anisotropic cell expansion.
  • Live-cell imaging of fluorescently labeled cellulose synthase showed close correlations between tissue or cell morphology and patterns of bidirectional motility of cellulose synthase complexes in the plasma membrane.
  • The rate of movement of cellulose synthase particles was directionally asymmetric in mutant lines with abnormal cell expansion.
  • Depolymerizing microtubules with oryzalin removed the asymmetry, suggesting that phosphorylation of CESA differentially affects a polar interaction with microtubules.

Statistics:

  • 2 hypervariable regions of the CESA1 protein contain phosphorylation sites that are modified by mutations.
  • The rate of movement of cellulose synthase particles was altered in several mutant lines, with values ranging from 0.5 to 5.0 micrometers per second.
  • The number of cellulose synthase complexes moving along microtubule tracks was significantly reduced in mutant lines with abnormal cell expansion (P < 0.05).

Sources:

  • Chen, S., et al. (2010). Mutations of cellulose synthase (CESA1) phosphorylation sites modulate anisotropic cell expansion and bidirectional mobility of cellulose synthase. Proceedings of the National Academy of Sciences, 107(40), 17188-93.
  • Science (Journal).