Intracellular magnetophoresis of amyloplasts and induction of root curvature

Abstract

High-gradient magnetic fields (HGMFs) were used to induce intracellular magnetophoresis of amyloplasts. The HGMFs were generated by placing a small ferromagnetic wedge into a uniform magnetic field or at the gap edge between two permanent magnets. In the vicinity of the tip of the wedge the dynamic factor of the magnetic field, delta(H2/2), was about 10(9) Oe2.cm-1, which subjected the amyloplasts to a force comparable to that of gravity. When roots of 2-d-old seedlings of flax (Linum usitatissimum L.) were positioned vertically and exposed to an HGMF, curvature away from the wedge was transient and lasted approximately 1 h. Average curvature obtained after placing magnets, wedge and seedlings on a 1-rpm clinostat for 2 h was 33 +/- 5 degrees. Roots of horizontally placed control seedlings without rotation curved about 47 +/- 4 degrees. The time course of curvature and changes in growth rate were similar for gravicurvature and for root curvature induced by HGMFs. Microscopy showed displacement of amyloplasts in vitro and in vivo. Studies with Arabidopsis thaliana (L.) Heynh. showed that the wild type responded to HGMFs but the starchless mutant TC7 did not. The data indicate that a magnetic force can be used to study the gravisensing and response system of roots.

Mechanisms of disruption of meristematic competence by microgravity inArabidopsisseedlings

“…Specifically, this is the case of starch granules which are the main component of statoliths, the starch-based organelles in the columella cells responsible of the gravitropism. 15 The consequences of this fact are multiple: in general, the different susceptibility to the magnetic field of various organelles may lead to an overall cellular readjustment, affecting differentially to the various cellular components; in particular, if statoliths do not levitate under water levitation conditions, seedlings will show conventional gravitropic responses at the 0g* position in the magnet. This means that disruption of meristematic competence in root meristematic cells resulting from magnetic levitation-induced effective microgravity is independent of statolith movements in columella cells and of gravitropic alterations in the root growth, but it is associated with auxin delocalization in the root tip.…”

Swimming Paramecium in magnetically simulated enhanced, reduced, and inverted gravity environments

“…Here, we will show that magnetic forces can be used to simulate variable gravity environments for paramecia. This work builds on previous studies using magnetic levitation (14)(15)(16) to simulate zero gravity for protein crystallization (17,18) and fluid dynamics experiments (19) and magnetic forces to alter gravitropism in plants (20). In an earlier report (21), a magnetic force buoyancy variation technique (MFBV) was introduced to vary the apparent weight of immobile cells with magnetic forces.…”

ALTERED RESPONSE TO GRAVITY Is a Peripheral Membrane Protein That Modulates Gravity-Induced Cytoplasmic Alkalinization and Lateral Auxin Transport in Plant Statocytes

“…Higher plant organs sense gravity primarily through the sedimentation of starch-filled amyloplasts in specialized cells called statocytes (Caspar and Pickard, 1989;Kiss et al, 1989;Kuznetsov and Hasenstein, 1996;Blancaflor et al, 1998). These cells constitute the columella of the root cap and the endodermal layer of the shoot.…”