CSB Special Seminar: Professor Edgar Spalding, Department of Botany, University of Wisconsin-Madison

Movement of the auxin (indole-3-acetic acid) through plant tissues and organs is as much a part of this hormone’s influence as the molecular actions by which it regulates much growth and development. Movement and action of the hormone were wrapped up into a vague notion called “correlation” by plant physiologists until the chemical identity of auxin was elucidated and phenomena such as tropisms were demystified almost 100 years ago. This presentation will survey the origins of the concept of a hormone with a highly controlled macroscopic transport mechanism before considering how well current information about PIN and ABCB membrane proteins supply a satisfactory explanation for the phenomenon usually referred to as polar auxin transport. Currently, most people believe that polar auxin transport results from auxin-conducting channels in the PIN family being localized predominantly at the ‘downstream’ ends of each cell in a path. The data from publications that established the current paradigm will be summarized along with new molecular, genetic, and electrophysiological data that indicate the mechanism may be more complicated. 

Selected Recent Publications

Wu G, Carville JS*, Spalding EP (2016) ABCB19-mediated polar auxin transport modulates Arabidopsis hypocotyl elongation and the endoreplication variant of the cell cycle. The Plant Journal 85: 209-218

Cho M, Henry EM, Lewis DR, Wu G, Muday GK, Spalding EP (2014) Block of ATP-binding cassette B19 ion channel activity by 5-nitro-2-(3-phenylpropylamino)-benzoic acid impairs polar auxin transport and root gravitropism Plant Physiology 166: 2091-2099

Moore CR, Johnson LS, Kwak I-Y, Livny M, Broman KW, Spalding EP (2013) High-throughput computer vision introduces the time axis to a quantitative trait map of a plant growth response. Genetics 195: 1077-1086

Vincill ED, Clarin AE, Molenda JN, Spalding EP (2013) Interacting glutamate receptor-like proteins in phloem regulate lateral root initiation. The Plant Cell 25: 1304-1313