Signal perception, transduction, and response in gravity resistance. Another graviresponse in plants

Mechanisms of disruption of meristematic competence by microgravity inArabidopsisseedlings

“…Furthermore, this effect may occur in absence of any alteration of auxin levels, as it is the case of cells in culture. whereas cell wall has been proposed as a gravity receptor, 28 mediators of the transduction of gravity mechanosignal sensed in this way are experimentally unknown. The protein kinase CK2 is proposed as a candidate to be part of this scheme in view of the experimental findings that put it in close relationship with some physiological and cellular processes involved, such as polar auxin transport, ribosome biogenesis, and cell cycle.…”

Cortical microtubules are responsible for gravity resistance in plants

“…We have termed this response 'gravity resistance', and examined its mechanism mainly using hypergravity conditions produced by centrifugation. 3,4 Plant protoplasts are surrounded by well-developed cell walls, which is the major source of mechanical strength for plant body. Therefore, the cell wall may be responsible for gravity resistance.…”

“…Actually, we have obtained evidence supporting this hypothesis. [2][3][4] Hypergravity has been shown to increase the cell wall rigidity in various plant materials. Hypergravity also caused an increase in cell wall thickness and a polymerization of certain matrix polysaccharides, such as xyloglucans in dicotyledons and 1,3,1,4-β-glucans in monocotyledonous Gramineae.…”

The Role of Brassinosteroids in Shoot Gravitropism

“…Nevertheless, reports have shown that resistance to hypergravity involves rigidification of the cell wall (Hoson et al, 2005(Hoson et al, , 2010, while microgravity results in more extensible cell walls by xyloglucan breakdown (Soga et al, 2002). We have found that BR treatment stimulates extension of frozen/thawed Arabidopsis hypocotyls at pH 6, which is indicative of changed cell wall properties.…”

“…This side consequently elongates more than the upper side, causing bending of the hypocotyl or stem (Morita and Tasaka, 2004;Esmon et al, 2006). To resist to the gravitational force, downstream regulation of cell wall remodeling and cell wall mechanics are thought to provide the necessary structural support (Hoson et al, 2005(Hoson et al, , 2010. Mutants with a defect in the formation of an endodermal layer, such as scarecrow (scr)/shoot gravitropism1, or with reduced starch production, such as phosphoglucomutase (pgm), have a defective graviresponse (Kiss et al, 1989;Fukaki et al, 1998).…”