Is the far-red-absorbing form of Avena phytochrome A that is present at the end of the day able to sustain stem-growth inhibition during the night in transgenic tobacco and tomato seedlings?

Abstract

Abstract. Arena phytochrome A (phyA) overexpressed in tobacco (Nicotiana tabacum L.) and tomato (Lycopersicon sculentum Mill) was functionally characterised by comparing wild-type (WT) and transgenic seedlings. Different proportions of phytochrome in its far-red-absorbing form (Pfr/P) were provided by end-of-day (EOD) light pulses. Stem-length responses occurred largely in the range of low Pfr/P (3-61%) for WT seedlings and in the range of high Pfr/P (61-87%) for transgenic seedlings. A similar shift was observed when the photoperiod was interrupted by short light pulses providing different Pfr/P ratios and followed by 1 h dark incubation. In other experiments, Arena phyA was allowed to re-accumulate in darkness and subsequently phototransformed to Pfr but no extra inhibition of stem extension growth was observed. In transgenic tomato seedlings the response to EOD far-red light was faster and the response to a far-red light pulse delayed into darkness was larger than in the WT. Arena phyA Pfr remaining at the end of the photoperiod appears intrinsically unable to sustain growth inhibition in subsequent darkness. Arena phyA modifies the sensitivity and the kinetics of EOD responses mediated by native phytochrome.

Light sensitivity changes during dormancy induction in Polygonum aviculare L. seeds: development of a predictive model of annual changes in seed‐bank light sensitivity in relation to soil temperature

“…The far‐red light (treatment 2) was provided by a 150 W incandescent reflector lamp (Phillips R95) in combination with a water filter and an RG9 filter (Schott). In treatment (3) (7.6 × 10 −4 Pfr/Pt), the flow rate of the incandescent lamp was reduced by a rheostat to obtain a lower photon flux (Scopel et al, 1991; Casal et al, 1995). During the exposure of the seeds to light treatments, the temperature in the cabinets was maintained at ca.…”

Stem Transcriptome Reveals Mechanisms to Reduce the Energetic Cost of Shade-Avoidance Responses in Tomato

“…Previous results had shown that mustard (Sinapis alba; Casal and Smith, 1988) and tomato (Casal et al, 1995) plants exposed to low R:FR for more than 3 h have elevated rates of stem growth after transfer to high R:FR. This was confirmed under the current conditions, as upon transfer to high R:FR, the stem of plants previously exposed to 4 h of low R:FR grew more during the subsequent 20 h (1.7 6 0.2 mm, P , 0.01, n = 42) than the plants previously exposed to only 1 h of low R:FR (1.1 6 0.1 mm) or high R:FR controls (1.0 6 0.1 mm).…”

Phytochromes, Cryptochromes, Phototropin: Photoreceptor Interactions in Plants

“…In tobacco or tomato plants overexpressing oat phyA, small reductions in the red to far-red ratio given at the end of the day are more effective than in the wild type (54). A direct relationship between phyA levels and the promotion of stem growth in response to reductions in end-of-day red to far-red ratio has been observed when potato plants transformed with the homologous gene of phyA in sense or anti-sense were compared to the wild type (55).…”