Skip to Main Content
 

Global Search Box

 
 
 
 

Files

File List


miami1218220626.pdf (4.11 MB)

ETD Abstract Container

Abstract Header

Cellular Mechanisms of Gravitropism in ARG1 (Altered Response to Gravity) Mutants of Arabidopsis Thaliana

Kumar, Neela Shiva
http://rave.ohiolink.edu/etdc/view?acc_num=miami1218220626

Abstract Details

2008, Doctor of Philosophy, Miami University, Botany.
Many studies have been conducted in an effort to understand the mechanisms involved in gravitropism. Gravity perception in plants occurs by the sedimentation of starch-filled plastids termed statoliths. These statoliths are located in the endodermal cells of stem-like organs and columella cells of the root cap. Plastids play an important role during the graviperception mechanism in plants in that they act as gravity sensors in the roots, hypocotyls and inflorescence stems of flowering plants. Gravity perception leads to signal transduction that eventually results in tropic curvature in plants. ARG1 (altered response to gravity) is a gene involved in gravitropism and encodes a DnaJ-like protein, suggesting its possible interaction with the cytoskeleton. We investigated whether the arg1 mutation affects gravitropism by modulating plastid sedimentation in gravity perceiving cells in Arabidopsis thaliana. By using cryofixation procedures and light microscopic studies, we have determined that ARG1 affects gravitropism in hypocotyls by reducing the plastid sedimentation process. The arg1-2 mutant exhibited reduced and delayed gravitropism in roots, shoots, and inflorescence stems in both light- and dark-grown conditions. We performed light microscopic studies of plastid movement in the gravity-perceiving statocytes (endodermal cells) of hypocotyls of arg1-2 and WT seedlings to better characterize the role of ARG1 in gravitropism. Cryofixation and freeze substitution procedures were used since these methods provide a reliable indication of rapid cellular events within the statocytes. We found that sedimentation of plastids in response to gravity in statocytes of the arg1-2 mutant was reduced and ARG1 affects gravitropism by reducing plastid movement/sedimentation, a process known to be essential for early phases of signaling cascades in the statocytes. The precise location of ARG1 protein within the columella cells has been further investigated by high resolution electron microscopy and indirect immunogold labeling suitable for Arabidopsis roots. These studies confirm that ARG1 is found specifically localized to the components of the endomembrane system such as Golgi apparatus, endoplasmic reticulum, secretory vesicles, and that this protein plays a key role in gravitropism. The significance of our study is that we have elucidated multiple roles of ARG1 both in gravity perception and signal transduction phase in statocytes.
Dr. John Z. Kiss (Advisor)
Dr. Q. Quinn Li (Committee Member)
Dr. Elisabeth E. Schussler (Committee Member)
Dr. M. Henry H. Stevens (Committee Member)
Dr. Lori G. Isaacson (Committee Member)
155 p.
Botany
ARG (altered response to gravity) protein; actin cytoskeleton; Arabidopsis; columella cells; electron microscopy; endodermis; endomembrane system; gravitropism; gravity perception; immunocytochemical; plastid movement; signal transduction; statocytes

Recommended Citations

Citations

  • Kumar, N. S. (2008). Cellular Mechanisms of Gravitropism in ARG1 (Altered Response to Gravity) Mutants of Arabidopsis Thaliana [Doctoral dissertation, Miami University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=miami1218220626

    APA Style (7th edition)

  • Kumar, Neela. Cellular Mechanisms of Gravitropism in ARG1 (Altered Response to Gravity) Mutants of Arabidopsis Thaliana. 2008. Miami University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=miami1218220626.

    MLA Style (8th edition)

  • Kumar, Neela. "Cellular Mechanisms of Gravitropism in ARG1 (Altered Response to Gravity) Mutants of Arabidopsis Thaliana." Doctoral dissertation, Miami University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=miami1218220626

    Chicago Manual of Style (17th edition)

miami1218220626
634
© 2008, all rights reserved.
This open access ETD is published by Miami University and OhioLINK.