Understanding phototropism: from Darwin to today

Abstract

Few individuals have had the lasting impact on such a breadth of science as Charles Darwin. While his writings about time aboard the HMS Beagle, his study of the Galapagos islands (geology, fauna, and flora), and his theories on evolution are well known, less appreciated are his studies on plant growth responses to a variety of environmental stimuli. In fact, Darwin, together with the help of his botanist son Francis, left us an entire book, 'The power of movements in plants', describing his many, varied, and insightful observations on this topic. Darwin's findings have provided an impetus for an entire field of study, the study of plant tropic responses, or differential growth (curvature) of plant organs in response to directional stimuli. One tropic response that has received a great deal of attention is the phototropic response, or curvature response to directional light. This review summarizes many of the most significant advancements that have been made in our understanding of this response and place these recent findings in the context of Darwin's initial observations.

Do Trees Grow on Money? Auxin as the Currency of the Cellular Economy

“…The modulation of auxin in response to abiotic changes in the environment is heavily documented, including a well-studied role for auxin in tropic responses to gravity (Morita and Tasaka 2004) and light (Holland et al 2009), a connection between auxin and response to salt stress (Wang et al 2009), and an interaction between auxin and high temperature (Gray et al 1998;Koini et al 2009). Just as the distribution of money by the government is affected by lobbyists and special interest groups, the developmental program is strongly influenced by information from the abiotic environment.…”

“…Blue light is perceived mainly by cryptochromes and phototropins, whereas red and far/red light is sensed by phytochromes. All three classes of photoreceptors have been linked with the auxin response (Chen et al 2004;Li and Yang 2007;Salisbury et al 2007;Holland et al 2009). Here, we focus on the phytochromes, as one example.…”

PIF4 and PIF5 Transcription Factors Link Blue Light and Auxin to Regulate the Phototropic Response in Arabidopsis

“…Phototropism is a rapid and visually striking adaptation response by which plant shoots grow toward a light source (Whippo and Hangarter, 2006;Holland et al, 2009). In Arabidopsis thaliana, blue light (BL), the predominant signal for phototropism, is perceived by the phototropin photoreceptors PHOTOTROPIN1 (PHOT1) and PHOT2, with PHOT1 acting as the main phototropin (Huala et al, 1997;Christie et al, 1998;Briggs et al, 2001).…”

The Signal Transducer NPH3 Integrates the Phototropin1 Photosensor with PIN2-Based Polar Auxin Transport in Arabidopsis Root Phototropism

“…Roots need to sense and respond appropriately to a diversity of environmental signals, such as gravity, mechanical impedance, light, humidity, oxygen, and essential nutrients, as well as to allelochemicals exuded from neighboring roots, to develop their optimal form or adapt to their environment conditions (Monshausen and Gilroy, 2009). Although phototropic responses in roots were discovered and analyzed some time ago, knowledge of root phototropism is surprisingly poor when compared with that of root gravitropism (Boonsirichai et al, 2002;Correll and Kiss, 2002;Whippo and Hangarter, 2006;Holland et al, 2009;Takahashi et al, 2009).…”