Genetic dissection of blue‐light sensing in tomato using mutants deficient in cryptochrome 1 and phytochromes A, B1 and B2

Abstract

SummarySeveral novel allelic groups of tomato (Solanum lycopersicum L.) mutants with impaired photomorphogenesis have been identi®ed after g-ray mutagenesis of phyA phyB1 double-mutant seed. Recessive mutants in one allelic group are characterized by retarded hook opening, increased hypocotyl elongation and reduced hypocotyl chlorophyll content under white light (WL). These mutants showed a speci®c impairment in response to blue light (BL) resulting from lesions in the gene encoding the BL receptor cryptochrome 1 (cry1). Phytochrome A and cry1 are identi®ed as the major photoreceptors mediating BL-induced de-etiolation in tomato, and act under low and high irradiances, respectively. Phytochromes B1 and B2 also contribute to BL sensing, and the relative contribution of each of these four photoreceptors differs according to the light conditions and the speci®c process examined. Development of the phyA phyB1 phyB2 cry1 quadruple mutant under WL is severely impaired, and seedlings die before¯owering. The quadruple mutant is essentially blind to BL, but experiments employing simultaneous irradiation with BL and red light suggest that an additional non-phytochrome photoreceptor may be active under short daily BL exposures. In addition to effects on de-etiolation, cry1 is active in older, WL-grown plants, and in¯uences stem elongation, apical dominance, and the chlorophyll content of leaves and fruit. These results provide the ®rst mutant-based characterization of cry1 in a plant species other than Arabidopsis.

A reverse genetics approach identifies novel mutants in light responses and anthocyanin metabolism in petunia

“…Arabidopsis is the sole plant species for which the full set of photoreceptor genes has been characterized (Demarsy and Fankhauser 2009;Inoue et al 2010;Nagatani 2010;Chaves et al 2011). In Solanaceae, photoperception and light signaling have been mainly investigated in tomato, tobacco and potato (Perrotta et al 2000;Weller et al 2001;Fernández et al 2005;Rutitzky et al 2009). High-throughput transcriptomic analyses have demonstrated extensive sequence and functional conservation among phenotypically distinct Solanaceae species potato, tomato, pepper, petunia, tobacco and Nicotiana benthamiana, although species-specific transcripts were also indentified (Rensink et al 2005;Rutitzky et al 2009).…”

“…Similarly, global gene-expression profiling in Nicotiana and Solanum species has demonstrated that light perception and signaling employ shared and exclusive pathways to control several photomorphogenic and photoperiodic responses (Rensink et al 2005;Rutitzky et al 2009). Petunia transcriptome exhibits high sequence and functional conservation to tomato transcript profiles (Rensink et al 2005) and, in this species deetiolation and anthocyanin biosynthesis are mainly controlled by phyA-and cry1-mediated signaling (Weller et al 2001). However, the overexpression of CRY2 has also led to enhanced anthocyanin accumulation in tomato fruits (Giliberto et al 2005;Lopez et al 2012).…”

“…Leaf number was counted from seedling emergency to senescence and leaf area was estimated from digitalized images of five leaves from plant apex. Total chlorophyll contents were estimated by spectrophotometric readings of dimethyl sulfoxide (DMSO) extracts at 649 and 665 nm (Weller et al 2001) and vegetative anthocyanin contents were determined under white and monochromatic b l u e l i g h t b y a ci d i c m e t h a n ol e x t r a c t i on s a n d spectrophotometric absorbance at 530 and 657 (Weller et al 2001).…”

The Negatively Acting Factors EID1 and SPA1 Have Distinct Functions in Phytochrome A-Specific Light Signaling

“…They are also responsible for the so-called low fluence responses (LFR) that exhibit the classical red/ far-red photoreversible characteristic of phytochrome function. LFR are normally induced by redlight photon fluences above approximately 1 mol m Ϫ2 (Furuya and Schäfer, 1996;Whitelam and Devlin, 1997;Neff et al, 2000;Weller et al, 2001).…”

“…Studies using phyA mutants and plants overexpressing phyA indicate that this photoreceptor is responsible for the very low fluence responses (VLFR) and for the far-red-light-dependent high-irradiance responses (HIR; Furuya and Schäfer, 1996;Whitelam and Devlin, 1997;Neff et al, 2000;Weller et al, 2001). Both responses do not show the classical red/far-red photoreversibility.…”