Effect of Strigolactone on Polar Auxin Transport and Plant Architecture

Physiologically, branching is regulated by a complex interplay of hormones including auxin, cytokinin and recently discovered strigolactone. The study is focused on the effect of strigolactone on shoot branching of pea (Pisum sativum L.) in relation with polar auxin transport, which has an essential role in apical dominance. After decapitation of the dominant apex lateral buds are released from growth inhibition and their outgrowth and elongation is initiated. Basipetal polar auxin transport system is realized by the downward movement of auxin from apical meristems towards the root system and strigolactone is transported acropetally. The polar auxin flow starts to be established in axillary buds, which is mediated by auxin efflux carriers PIN1 proteins localized on the basal end of cells. Exogenous application of GR24 synthetic analogue of strigolactone on the second or third bud of 7 day-plants led to partial growth inhibition of treated bud which is apparently associated with gene expression changes. Expression profiles of PIN1 and DRM1 genes and immunocytolocalizations of PIN1 proteins are studied, to reveal and understand how strigolactone interacts with polar auxin transport on transcriptional and translational levels. The gene expression and polarization of PIN1 proteins after short-time and long-time influence of strigolactone on the axillary bud was followed.