Expression and regulation of PIN1 and AUX1 genes encoding carrier proteins for auxin polar transport in higher plants: Relevance to effects of chemicals and simulated microgravity conditions on a three-dimensional clinostat

Abstract

Under true microgravity conditions in space as well as simulated ones on a three-dimensional clinostat, etiolated pea seedlings showed automorphosis-like growth, which was phenocopied by auxin polar transport inhibitors on 1 g conditions. Since auxin polar transport in etiolated pea seedlings grown in space were substantially reduced, these suggest an important role of auxin polar transport in the regulation of automorposis. Auxin polar transport is regulated by putative PsPIN1 and PsAUX1 in etiolated pea seedlings. Significantly high homology on nucleotide sequences was found between PsPIN1 and AtPIN. Expression of PsPIN1 and PsAUX1 in etiolated pea seedlings was substantially observed. Studies of the effects of auxin polar transport inhibitors as well as simulated microgravity conditions on expression of PsPIN1 and PsAUX1 in etiolated pea seedlings are now on progress. A possible role of gravity for auxin polar transport in higher plants will also be discussed.