Signaling in Phototropism

Understanding phototropism: from Darwin to today

“…While the details of this process still remain largely unknown, several components of this 'black box' have been identified, most notably three phot1-interacting proteins: NPH3 (NON-PHOTOTROPIC HYPOCOTYL 3; Motchoulski and Liscum, 1999), RPT2 (ROOT PHOTOTROPISM 2; Inada et al, 2004), and PKS1 (PYTOCHROME KINASE SUBSTRATE 1; Lariquet et al, 2006). NPH3 and RPT2 are paralogous proteins that represent the founding members of the moderately sized NRL (NPH3/RPT2-Like) protein family (33 members in total) in Arabidopsis (Celaya and Liscum, 2005;Celaya et al, 2009). Members of the NRL family, including NPH3 and RPT2, share five regions of primary sequence conservation ( Fig.…”

“…In the presence of elevated levels of free auxin, MSG2/IAA19 and AXR5/ IAA1 are rapidly degraded by a 26S proteasome that requires the SCF TIR1 complex containing the auxin receptor TIR1 to target these proteins for degradation (Tan et al, 2007). This, in turn, allows homodimerization of the NPH4/ ARF7 protein and transcription of 'auxin responsive genes' (Tatematsu et al, 2004;Celaya et al, 2009). A recent transcript profiling study in Brassica oleracea has identified a number of genes that appear to represent targets of NPH4/ARF7 regulation in response to tropic stimulation; these include genes encoding proteins involved in the regulation of free auxin levels, additional transcriptional regulators, and proteins involved in the regulation of cell wall extensibility (Esmon et al, 2006).…”

The “sensational” power of movement in plants: A Darwinian system for studying the evolution of behavior

“…Progress in the fi eld was slow and confusion abounded ( Firn and Digby, 1980 ). Excellent reviews concerning the genetics and molecular biology of various forms of plant movement can be found elsewhere ( Braam, 2005 ;Esmon et al, 2005 ;Iino, 2006 ;Mc-Clung, 2006 ;Celaya et al, 2009 ;Isnard and Silk, 2009 ). In fairly quick succession, numerous plant movement mutants were isolated ( Mirza et al, 1984 ;Khurana and Poff, 1989 ;Okada and Shimura, 1992 ;Liscum and Briggs, 1995 ).…”

“…By genetically mapping many of these mutants, dozens of genes encoding proteins involved in plant movements have since been identifi ed, and the underlying molecular mechanisms are rapidly being revealed. Excellent reviews concerning the genetics and molecular biology of various forms of plant movement can be found elsewhere ( Braam, 2005 ;Esmon et al, 2005 ;Iino, 2006 ;Mc-Clung, 2006 ;Celaya et al, 2009 ;Isnard and Silk, 2009 ).…”