Phototropins and chloroplast activity in plant blue light signaling

Abstract

In plants, phototropins 1 (phot1) and 2 (phot2) mediate chloroplast movement to blue light (BL). A recent report showed that phototropins (phot) are required for the expression of chloroplast genes in rice. The light-induced responses of phot1a rice mutants result in H 2 O 2 -mediated damage to chloroplast photosystems, indicating that phot-regulated responses might be associated with the other photoreceptor, such as cryptochrome (cry) BL receptor. This suggests diversification and specialization of photoreceptor signaling in plants.In order to counteract the adverse effects of environmental ight, plants have evolved sensory mechanisms that monitor their surroundings and adapt their growth and development through the use of a complex signaling network. 1 Plants sense their environmental light conditions by using three principal families of signal-transducing photoreceptors; the red/far-red (R/FR) light-absorbing phytochromes (phy) and the UV-A/blue light (BL)-absorbing cryptochromes (cry) and phototropins (phot). 2 The phys are reversibly photochromic biliproteins that absorb maximally in the R and FR light regions of the spectrum. Cry and phot possess a pair of flavin derivates. Two cry and two phot family members have been identified and well characterized in Arabidopsis. Photoreceptors regulate development throughout the plant lifecycle, from seed germination through to plant maturation and the onset of reproduction. BL regulates a wide variety of photoresponses in higher plants, including chloroplast movement, inhibition of hypocotyls elongation, circadian timing, regulation of gene expression and stomatal opening. [3][4][5] The roles of individual photoreceptors in mediating plant development have, however, often been confounded by redundant, synergistic and in some cases mutually antagonistic mechanisms of action. The mechanisms of photoreceptor signal transduction are far from being completely elucidated, but are believed to involve both cytosolic and nuclear components. The presence of putative kinase domains within photoreceptor proteins has suggested a role for phosphorylation in light signaling. The action of cry1 and cry2 has been demonstrated to involve BL-mediated autophosphorylation. 6,7 Phot1 was originally identified as a 120 kDa-membrane associated protein displaying BL-mediated autophosphorylation. 8 It is now well accepted that phot mediates chloroplast movement, phototropism and stomatal opening in plants in response to BL. Phototropin BL ReceptorsRecent genetic studies using mutant Arabidopsis revealed that at least two distinct types of BL receptors are responsible for BL-induced responses. Microarray analysis suggested that cryptochromes (cry1 and cry2) independently function as key regulators of early BL-induced genes, whereas phototropins (phot1 and phot2, formerly known as NPH1 and NPL1) play subsidiary roles in transcriptional regulation by BL. 9 Cry functions mainly in photomorphogenic responses involving the regulation of photoinduced movement. The cry signaling mechanism in Arabido...

Effect of short-term exposure to red and blue light on dill plants growth

“…In contrast, blue light is important in the formation of chlorophyll, chloroplast development, stomatal opening, enzyme synthesis, activation of the circadian rhythm of photosynthesis, and photomorphogenesis (Christie 2007;Kang et al 2008;Demarsy, Frankhauser 2009;Goh 2009). Physiological responses to spectral changes can vary among diff erent plant species (Hirai et al 2006).…”

Comparison between the Transcriptomes of ‘KDML105’ Rice and a Salt-Tolerant Chromosome Segment Substitution Line

“…The expression of rice phototropin 2 ( OsPHOT2 ) was shown to be induced by white, blue, red, and far-red light [27]. Phototropin was also shown to be involved in chloroplast movement and was required for chloroplast gene expression [28]. While there is no published evidence of the involvement of OsPHOT in the salt stress response, our results suggest that OsPHOT2 may contribute to the salt-tolerant phenotype of CSSL18.…”

Light quality, oxygenic photosynthesis and more

“…It deals with the regulation of plant growth under a broad range of light intensities and wavelengths and allows plants to optimize their use of light and space. For this, plants have acquired several major photoreceptor molecules, including phytochromes (PHY; Franklin and Quail 2010), and two types of blue-light photoreceptors, cryptochromes (CRY; Yu et al 2010, Chaves et al 2011, and phototropins (PHOT; Christie and Briggs 2001, Lin 2002, Christie 2007, Goh 2009. These plant photoreceptors are implicated in direct perception, and/or modulation of responses, of a wide range of environmental cues, or to plant development stages and responses to dynamic environmental stimuli (D'Amico-Damião and Carvalho 2018, Paik and Huq 2019).…”

“…Arabidopsis contains several blue-light photoreceptors, including two types of PHOT (PHOT1 and PHOT2; Lin 2002, Harper et al 2003, Christie 2007, Goh 2009 and three types of CRY (CRY1, CRY2, and CRY3, also called CRY-DASH; Wang and Lin 2020). The receptors PHOT1 and PHOT2 mediate phototropism (i.e., turgordriven movement of a plant organ away or toward from a light source; see e.g., Liscum et al 2020), as well as stomatal and chloroplast movement (Briggs andChristie 2002, Christie et al 2015), which play an important role in the optimization of photosynthesis.…”