Live-cell imaging of plant gravity sensing by using a vertical-stage confocal microscope and a centrifuge microscope

Abstract

Gravity is a ubiquitous force on the earth and a crucial environmental signal for living organisms. To adapt and survive in the gravitational field, plants sense the gravity vector (magnitude and direction) and change their morphology accordingly. These are widespread phenomena known as 'gravity resistance' and 'gravitropism'. We have studied the early process of shoot gravitropism, gravity sensing, using molecular genetic techniques in combination with two novel microscopes, a vertical-stage confocal microscope and a centrifuge microscope. The vertical-stage confocal microscope is a vertically oriented microscope equipped with a rotatable stage, a spinning-disk confocal scanning unit and a back-illuminated EM-CCD camera, which allows fluorescence imaging of the Arabidopsis stem specimen before and after gravistimulation (changes in the direction of gravity). The centrifuge microscope is a spinning upright microscope equipped with a radio system, which allows bright-field imaging during centrifugation (changes in the magnitude of gravity). In this review, we will introduce the recently developed microscopes that are essential to gain new insights into gravity sensing mechanisms in Arabidopsis inflorescence stems.