Involvement of phytochrome A in suppression of photomorphogenesis in rice seedling grown in red light

Abstract

Plants have evolved a remarkable capacity to track and respond to fluctuations of light quality and intensity that influence photomorphogenesis facilitated through several photoreceptors, which include a small family of phytochromes. Rice seedlings grown on germination paper in red light for 48 h having their shoot bottom exposed had suppressed photomorphogenesis and were deficient in chlorophyll. Seedlings grown under identical light regime having their shoot bottom covered were green and accumulated chlorophyll. Further, etiolated seedlings with their shoot bottom exposed, when grown in 4 min red/far-red cycles for 48 h, accumulated chlorophyll demonstrating the reversal of suppression of photomorphogenesis by far-red light. It implicates the involvement of phytochrome. Immunoblot analysis showed the persistence of photolabile phytochrome A protein for 48 h in seedlings grown in red light with their shoot bottom exposed, suggesting its involvement in suppression of photomorphogenesis. This was further corroborated in phyA seedlings that turned green when grown in red light having their shoot bottom exposed. Calmodulin (CaM) antagonist N-(6-aminohexyl)-5-chloro-1-napthalene sulphonamide or trifluoperazine substantially restored photomorphogenesis both in the wild type (WT) and phyA demonstrating the involvement of CaM-dependent kinases in the down-regulation of the greening process. Results demonstrate that red light-induced suppression of photomorphogenesis, perceived in the shoot bottom, is a red high irradiance response of PhyA.

Control of Adventitious Root Architecture in Rice by Darkness, Light, and Gravity

“…Absorbance of far-red light by Pfr converts the active phytochrome to its inactive form Pr (Li et al, 2011). In rice, phytochromes are encoded by three genes, PhyA to PhyC, whereby PhyA is responsible mainly for mediating photomorphogenic responses Roy et al, 2013). Some physiological responses, such as shade avoidance, depend on the ratio of Pr to Pfr.…”

Light-hormone interaction in the red-light-induced suppression of photomorphogenesis in rice seedlings

“…LED arrays (Q-BEAM, Quantum Devices, Barneveld, WI, USA) were used as sources of R and B lights. More details about the LEDs can be obtained from Roy et al (2013). Light intensities falling on the plants were measured by a Licor spectroradiometer (Li-Cor Biosciences, Lincoln, NE, USA).…”

“…Semi-quantitative RT-PCR was performed as described by Roy et al (2013). Reaction contained selected couples of gene-specific primers (Supplementary Table 1 in supporting information).…”

“…In previous studies, we have shown rice and wheat seedling grown with their shoot bottom exposed to constant red light or when given in the form of light-dark cycles do not accumulate chlorophyll (Chl) (Gupta et al 2010;Roy et al 2013;Sood et al 2005;Sood et al 2004;Tripathy and Brown 1995). Red light perceived by the shoot bottom downregulates the protein and gene expression of the enzymes involved in the biosynthesis of tetrapyrroles (Sood et al 2005;Sood et al 2004;Tripathy and Brown 1995).…”

“…Red light perceived by the shoot bottom downregulates the protein and gene expression of the enzymes involved in the biosynthesis of tetrapyrroles (Sood et al 2005;Sood et al 2004;Tripathy and Brown 1995). This red-light-induced suppression of photomorphogenesis is a red high-irradiance response (red HIR) of PhyA (Roy et al 2013).…”