Nebenführ, Andreas , Park, Eunsook , Soltanian, Niloufar .
Myosin motors are required for optimal tip growth of root hairs.
Root hairs grow only at their tip, i.e. by targeted addition of cell wall material within an apical dome. This tip growth is supported by substantial cytoplasmic streaming along the shaft of the hair with velocities around 2 to 3 Āµm/s for Arabidopsis thaliana. It is generally assumed that the streaming movements are necessary to supply membrane and cell wall material as well as energy to the growing tip. To investigate the role of these organelle movements in the delivery of secretory vesicles to the tip we have isolated mutants in myosin genes. Two mutants were found to result in reduced root hair elongation. Disruption of the XI-K gene by T-DNA insertion resulted in shorter root hairs with only 70 % the length of WT. Another mutant, mya1, did not result in shorter root hairs by itself, but in combination with xi-k caused even shorter root-hairs (45 % of WT). The reduced root hair length and the nature of the disrupted genes suggested that organelle movement in these root hairs might be impaired. Interestingly, cytoplasmic streaming velocities in single and double-mutant root hairs are within in the same range as for wild-type when observed with DIC optics. This suggested that only the movements of specific organelles may be impaired in mutant cells. We have therefore transformed a number of fluorescent organelle markers into the mutants and wild-type to observe movement and distribution of specific organelles. Preliminary evidence suggests that the distribution of YFP-RabA4b-labeled structures is abnormal in the mutant which might be related to the reduced elongation phenotype. A detailed analysis of the distribution of these and several other organelles in WT and mutant root hairs will be presented. This work is supported by NSF grant MCB-0416931.
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1 - University of Tennessee, Biochemistry, Cellular and Molecular Biology, M407 Wanters Life Sciences, Knoxville, TN, 37996-0840, USA
2 - University of Tennessee, Biochemistry, Cellular and Molecular Biology
Presentation Type: ASPB Minisymposium
Location: Continental B/Hilton
Date: Wednesday, July 11th, 2007
Time: 11:55 AM