Perception mechanism of gravistimuli in gravity resistance responses of plants.
Gravity resistance is a response that enables plants to develop against the gravitational force. Hypergravity conditions produced by centrifugation have been used to analyze the mechanisms of gravity resistance responses. Under hypergravity conditions, plants construct short and thick shoots and increase cell wall rigidity for resisting the gravitational force. Hypergravity caused a decrease in the percentage of cells with transverse microtubules, and an increase in that with longitudinal microtubules. Such a prompt reorientation of cortical microtubules is involved in the changes in morphology of shoots by gravity. Hypergravity increased cell wall rigidity by increasing the molecular mass of xyloglucans via suppression of xyloglucan breakdown as well as by the thickening of cell walls. Blocker reagents of mechanoreceptors nullified the above-mentioned changes induced by hypergravity. Gravity resistance responses were brought about normally in mutants deprived of gravitropism. This result indicates that the graviperception mechanism in gravity resistance is independent of that in gravitropism. Gravity resistance responses were brought about independently of the direction of gravistimuli, but the responses disappeared in the presence of blockers of mechanoreceptors. Thus, in gravity responses, plants may perceive the gravitational force independently of the direction of stimuli by mechanoreceptors on the plasma membrane, and may utilize the signal to construct a tough body.
Soga
Kouichi
K
Dept. Biol., Grad. Sch. Sci., Osaka City Univ.
D017360:Arabidopsis / Q000235:genetics; D002473:Cell Wall / Q000502:physiology*; D007887:Fabaceae; D006112:Gravitation; D018522:Gravitropism / Q000502:physiology*; D018466:Gravity Sensing / Q000502:physiology*; D018471:Hypergravity; D015398:Signal Transduction / Q000502:physiology*