Search Results (25)

Early and recent studies have demonstrated that exposure to moonlight influences the entire life cycle of plants from seed germination to vegetative growth and reproduction. Exposure to moonlight was found to induce genome reorganization in plants and significant changes in gene expression, protein, and metabolite profiles. However, the specific factors that facilitate moonlight perception are unknown. To uncover the photoreceptors responsible for moonlight perception, we analyzed Arabidopsis phototropin mutants (phot1, phot2, and phot1phot2) as well as the phytochrome mutants phyA and phyB for their response to full moonlight (FML). De-etiolation assays revealed that plants do perceive and respond to FML within 5 h of exposure. Thus, among the photoreceptor mutants analyzed, only phot1 and phot1phot2 were impaired in apical hook opening and cotyledon unfolding under FML. Interestingly, under high light intensity, all examined mutants underwent proper de-etiolation. Further analysis showed that phot1 as well as phyB mutants were impaired in response to moonlight, displaying no changes in nuclear size and in protein profiles following exposure to FML and were comparable to plants exposed to dark. The FML (5 h exposure) did not induce the formation of fewer, large nuclear photobodies, as occurred following 5 h exposure to growth-room light. Our findings highlighted phot1 and phyB as photoreceptors necessary for plants to perceive and respond to FML. It is proposed that the initial perception of moonlight is facilitated by the blue-light receptor phot1 and is subsequently interpreted into a functional state by the R/FR receptor phyB. Full article

Stem mustard (Brassica juncea var. tumida Tsen et Lee) is an important economic vegetable in China. Premature bolting induced by temperature fluctuations has become a major cultivation constraint. Photoreceptors (PHRs) serve as critical photosensor proteins that interpret light signals and regulate physiological responses in plants. In this study, five core PHR families, namely F-box-containing flavin binding proteins (ZTL/FKF1/LKP2), phytochrome (PHY), cryptochrome (CRY), phototropin (PHOT) and UV RESISTANCE LOCUS 8 (UVR8) were identified in Brassica species. RNA-seq analysis revealed their expression patterns during organogenesis in B. juncea. Seven candidate PHRs were validated by qRT-PCR in B. juncea early-bolting (‘YA-1’) and late-bolting (‘ZT-1’) cultivars. Agrobacterium-mediated BjuFKF1_1 overexpression (OE) lines resulted in significantly earlier flowering under field conditions. Histochemical GUS staining indicated that BjuFKF1_1 was expressed in seedlings, leaves, flower buds and siliques. Transcript analysis revealed that the expression level of BjuFKF1_1 was up-regulated in all tissues at both the vegetative and reproductive stages, whereas the expression of BjuFKF1_1 interacting protein-encoding genes were down-regulated in flowers. Under blue light, genes encoding interacting proteins (BjuCOL5, BjuSKP1, BjuCOL3, BjuAP2, BjuAP2-1 and BjuLKP2) were up-regulated in flower buds, whereas BjuCOL and BjuPP2C52 were down-regulated in flowers. Developmental stage analysis revealed the up-regulation of five (BjuAP2, BjuCOL3, BjuCOL5, BjuAP2-1 and BjuLKP2) and four (BjuCOL, BjuCOL5, BjuAP2 and BjuLKP2) interaction protein-encoding genes during the reproductive stage under white and blue light, respectively. These findings elucidate the role of BjuFKF1_1 in flowering regulation and provide molecular targets for B. juncea bolting-resistant variety breeding. Full article

Phototropins (PHOTs) are plant blue-light receptors that mediate crucial physiological processes such as phototropism, chloroplast movement, stomatal opening, and flowering. However, the PHOT family genes remain poorly characterized in pepper. Here, we identified and molecularly cloned two PHOT genes (CaPHOT1 and CaPHOT2) in pepper, which were phylogenetically classified into distinct groups with their homologs from rice, maize, tomato, and Arabidopsis. These genes exhibit conserved gene structures, implying functional conservation during evolution. Subcellular localization analysis confirmed that both CaPHOT1 and CaPHOT2 are localized to the plasma membrane. Expression profiling revealed that both CaPHOT1 and CaPHOT2 were expressed in all tissues, with the highest transcripts in leaves and the lowest in roots. Notably, RNA-seq data revealed that the expression of CaPHOT1 was up-regulated by JA and SA, whereas CaPHOT2 showed no significant changes. Furthermore, CaPHOT1 and CaPHOT2 displayed divergent expression patterns upon Phytophthora capsici infection (PCI). Furthermore, transient overexpression of CaPHOT1 in pepper enhanced susceptibility to PCI, indicating its negative role in disease resistance. Our findings identified the CaPHOT gene family in pepper and functionally demonstrated that CaPHOT1 negatively regulates resistance to PCI, thereby providing insights for future research on PHOTs in other plant species. Full article

(1) Background: The complete signalling pathway leading to light-induced chloroplast movement in plant cells is not yet fully understood. The process may involve GLR channels, which have previously been shown to participate in light signalling in plants. Therefore, using in vivo photometry we analysed chloroplast movements in the water plant Lemna trisulca treated with GLR channel inhibitors, MK-801 and CNQX. (2) Results: MK-801, a non-competitive antagonist that blocks NMDA channels was found to inhibit the avoidance response of chloroplasts controlled by phototropin2. This inhibition depends on pH and requires alkaline conditions. On the contrary, CNQX, a competitive receptor antagonist that blocks AMPA channels did not change the parameters of chloroplast movements in either mild alkaline or acidic conditions. (3) Conclusions: Our study reveals that GLR NMDA channels play a role in chloroplast movements and provides new insights into the phot2 signalling pathway. The results also suggest that the activity of these channels depends on pH, similar to NMDA receptors present in animal cells. Full article

Phototropins (PHOTs), as blue light receptors, play a pivotal role in plant light signal perception and adaptive regulation, yet their functional characteristics in trees remain poorly understood. In this study, the PHOT gene family was identified in Populus trichocarpa, and it included three members, PtrPHOT1, PtrPHOT2.1, and PtrPHOT2.2, all of which were highly expressed in mature leaves. Using CRISPR/Cas9 gene editing technology, triple-gene mutations in the PtrPHOT1/2.1/2.2 (PtrPHOTs) were generated, providing initial insights into the functions of PHOTs in trees. Compared to the wild type (WT), triple-gene ptrphots mutants displayed curved and wrinkled leaves, reduced leaf area, and delayed phototropic responses, indicating the central role of PHOTs in blue light signal perception. The stomatal aperture recovery rate in mutants was only 40% of that observed in WT, accompanied by significant downregulation of the BLUS1 gene transcription levels, confirming the conservation of the PHOT-BLUS1-H⁺-ATPase signaling axis in stomatal regulation. Transcriptome of triple-gene ptrphots mutants revealed 1413 differentially expressed genes, of which were enriched in auxin response (upregulation of SAUR family genes), jasmonic acid (downregulation of JAZ genes), and light signaling pathways, suggesting that PHOTs could regulate plant adaptability by integrating light signals and hormone homeostasis. Overall, this study achieved the knockouts of three PtrPHOTs family genes, and characteristics of triple-gene ptrphots mutants elucidated the multifunctional roles of PHOTs in leaf development, phototropism, and stomatal movement in poplar. Our work provides a foundation for deciphering light signaling networks and molecular breeding in woody plants. Full article

Chloroplast movement rapidly ameliorates the effects of suboptimal light intensity by accumulating along the periclinal cell walls, as well as the effects of excess light by shifting to the anticlinal cell walls. These acclimation responses are triggered by phototropins located at the plasma membrane and chloroplast envelope. Here, we used a recently developed non-invasive system sensitive to very small changes in red light leaf transmittance to perform long-term continuous measurements of dark–light transitions. As a model system, we used variegated Pelargonium zonale leaves containing green sectors (GS) with fully developed chloroplasts and achlorophyllous, white sectors (WS) with undifferentiated plastids, and higher phototropin expression levels. We observed biphasic changes in the red-light transmittance and oscillations triggered by medium intensities of white light, described by a transient peak preceded by a constant decrease in transmittance level. A slight change in red-light transmittance was recorded even in WS. Furthermore, the chloroplast position at lower light intensities affected the rapid light curves, while high light intensity decreased saturated electron transport, maximum quantum efficiency of photosystem II, and increased non-photochemical quenching of chlorophyll fluorescence and epidermal flavonoids. Our results extend the knowledge of light-dependent chloroplast movements and thus contribute to a better understanding of their role in regulating photosynthesis under fluctuating light conditions. Full article

In this contribution, we describe a brief overview of the role of different light-signaling proteins in different biochemical processes (mostly in plants) along the electromagnetic spectrum. We also revise, in terms of perspectives, the applications of all these proteins to optogenetics as a new emerging field of research. In the second part, we present some case studies: First, we used two fluorescent proteins showing an optical response in the green- and red-light wavelengths both isolated from marines’ organisms, which were incorporated as light sensors into the silico-carbonate of Ca, Ba, and Sr (usually called biomorphs). The second case study consisted in incorporating phototropins from a plant (Arabidopsis thaliana) into the synthesis of biomorphs. Finally, the last part analyses the influence of these three proteins on the shape and structure in the synthesis of silico-carbonates of calcium, barium, and strontium as optical sensors, in order to detect the location of these biomolecules inside these self-assembly crystalline materials called biomorphs. Full article

The root is an important organ for obtaining nutrients and absorbing water and carbohydrates, and it depends on various endogenous and external environmental stimulations such as light, temperature, water, plant hormones, and metabolic constituents. Auxin, as an essential plant hormone, can mediate rooting under different light treatments. Therefore, this review focuses on summarizing the functions and mechanisms of light-regulated auxin signaling in root development. Some light-response components such as phytochromes (PHYs), cryptochromes (CRYs), phototropins (PHOTs), phytochrome-interacting factors (PIFs) and constitutive photo-morphorgenic 1 (COP1) regulate root development. Moreover, light mediates the primary root, lateral root, adventitious root, root hair, rhizoid, and seminal and crown root development via the auxin signaling transduction pathway. Additionally, the effect of light through the auxin signal on root negative phototropism, gravitropism, root greening and the root branching of plants is also illustrated. The review also summarizes diverse light target genes in response to auxin signaling during rooting. We conclude that the mechanism of light-mediated root development via auxin signaling is complex, and it mainly concerns in the differences in plant species, such as barley (Hordeum vulgare L.) and wheat (Triticum aestivum L.), changes of transcript levels and endogenous IAA content. Hence, the effect of light-involved auxin signaling on root growth and development is definitely a hot issue to explore in the horticultural studies now and in the future. Full article

Rhythmic exposure to moonlight has been shown to affect animal behavior, but its effects on plants, often observed in lunar agriculture, have been doubted and often regarded as myth. Consequently, lunar farming practices are not well scientifically supported, and the influence of this conspicuous environmental factor, the moon, on plant cell biology has hardly been investigated. We studied the effect of full moonlight (FML) on plant cell biology and examined changes in genome organization, protein and primary metabolite profiles in tobacco and mustard plants and the effect of FML on the post-germination growth of mustard seedlings. Exposure to FML was accompanied by a significant increase in nuclear size, changes in DNA methylation and cleavage of the histone H3 C-terminal region. Primary metabolites associated with stress were significantly increased along with the expression of stress-associated proteins and the photoreceptors phytochrome B and phototropin 2; new moon experiments disproved the light pollution effect. Exposure of mustard seedlings to FML enhanced growth. Thus, our data show that despite the low-intensity light emitted by the moon, it is an important environmental factor perceived by plants as a signal, leading to alteration in cellular activities and enhancement of plant growth. Full article

The CRISPR/Cas9 system has been widely applied as a precise gene-editing tool for studying gene functions as well as improving agricultural traits in various crop plants. Here, we optimized a gene-editing system in lettuce (Lactuca sativa L.) using the endogenous U6 promoter and proved that the PHOT2 gene is a versatile target gene. We isolated the LsU6-10 promoter from 10 U6 snRNA genes identified from the lettuce genome database for comparison with the AtU6-26 promoter that has been used to drive sgRNAs in lettuce. Two CRISPR/Cas9 vectors were constructed using the LsU6-10 and AtU6-26 promoters to drive sgRNA361 to target the PHOT2 gene. The chloroplast avoidance response was defective in lettuces with biallelic mutations in the targeted PHOT2 gene, as in the Arabidopsis phot2 mutant. The PHOT2 gene mutations were stably heritable from the R0 to R2 generations, and the high gene-editing efficiency enabled the selection of transgene-free lines in the R1 generation and the establishment of independent phot2 mutants in the R2 generation. Our results suggest that the LsU6-10 promoter is more effective than the AtU6-26 promoter in driving sgRNA for the CRISPR/Cas9 system in lettuce and that PHOT2 is a useful target gene to verify gene editing efficiency without any detrimental effects on plant growth, which is often a consideration in conventional target genes. Full article

Plants have mechanisms to relocate chloroplasts based on light intensities in order to maximize photosynthesis and reduce photodamage. Under low light, chloroplasts move to the periclinal walls to increase photosynthesis (accumulation) and move to the anticlinal walls under high light to avoid photodamage, and even cell death (avoidance). Arabidopsis blue light receptors phot1 and phot2 (phototropins) have been reported to regulate chloroplast movement. This study discovered that another blue light receptor, FLAVIN-BINDING KELCH REPEAT F-BOX1 (FKF1), regulates chloroplast photorelocation by physically interacting with chloroplast unusual positioning protein 1 (CHUP1), a critical component of the chloroplast motility system. Leaf cross-sectioning and red-light transmittance results showed that overexpression of FKF1 compromised the avoidance response, while the absence of FKF1 enhanced chloroplast movements under high light. Western blot analysis showed that CHUP1 protein abundance is altered in FKF1 mutants and overexpression lines, indicating a potential regulation of CHUP1 by FKF1. qPCR results showed that two photorelocation pathway genes, JAC1 and THRUMIN1, were upregulated in FKF1-OE lines, and overexpression of FKF1 in the THRUMIN1 mutant weakened its accumulation and avoidance responses, indicating that JAC1 and THRUMIN1 may play a role in the FKF1-mediated chloroplast avoidance response. However, the precise functional roles of JAC1 and THRUMIN1 in this process are not known. Full article

UV-B and UV-A radiation are natural components of solar radiation that can cause plant stress, as well as induce a range of acclimatory responses mediated by photoreceptors. UV-mediated accumulation of flavonoids and glucosinolates is well documented, but much less is known about UV effects on carotenoid content. Carotenoids are involved in a range of plant physiological processes, including photoprotection of the photosynthetic machinery. UV-induced changes in carotenoid profile were quantified in plants (Arabidopsis thaliana) exposed for up to ten days to supplemental UV radiation under growth chamber conditions. UV induces specific changes in carotenoid profile, including increases in antheraxanthin, neoxanthin, violaxanthin and lutein contents in leaves. The extent of induction was dependent on exposure duration. No individual UV-B (UVR8) or UV-A (Cryptochrome or Phototropin) photoreceptor was found to mediate this induction. Remarkably, UV-induced accumulation of violaxanthin could not be linked to protection of the photosynthetic machinery from UV damage, questioning the functional relevance of this UV response. Here, it is argued that plants exploit UV radiation as a proxy for other stressors. Thus, it is speculated that the function of UV-induced alterations in carotenoid profile is not UV protection, but rather protection against other environmental stressors such as high intensity visible light that will normally accompany UV radiation. Full article

Photosensory proteins known as photoreceptors (PHRs) are crucial for delineating light environments in synchronization with other environmental cues and regulating their physiological variables in plants. However, this has not been well studied in the Brassica genus, which includes several important agricultural and horticultural crops. Herein, we identified five major PHR gene families—phytochrome (PHY), cryptochrome (CRY), phototropin (PHOT), F-box containing flavin binding proteins (ZTL/FKF1/LKP2), and UV RESISTANCE LOCUS 8 (UVR8)—genomic scales and classified them into subfamilies based on their phylogenetic clustering with Arabidopsis homologues. The molecular evolution characteristics of Brassica PHR members indicated indirect expansion and lost one to six gene copies at subfamily levels. The segmental duplication was possibly the driving force of the evolution and amplification of Brassica PHRs. Gene replication retention and gene loss events of CRY, PHY, and PHOT members found in diploid progenitors were highly conserved in their tetraploid hybrids. However, hybridization events were attributed to quantitative changes in UVR8 and ZTL/FKF1/LKP2 members. All PHR members underwent purifying selection. In addition, the transcript expression profiles of PHR genes in different tissue and in response to exogenous ABA, and abiotic stress conditions suggested their multiple biological significance. This study is helpful in understanding the molecular evolution characteristics of Brassica PHRs and lays the foundation for their functional characterization. Full article

Phototropins (phot1 and phot2) are plant-specific blue light receptors that mediate chloroplast movement, stomatal opening, and phototropism. Phototropin is composed of the N-terminus LOV1 and LOV2 domains and the C-terminus Ser/Thr kinase domain. In previous studies, 35-P2CG transgenic plants expressing the phot2 C-terminal fragment–GFP fusion protein (P2CG) under the control of 35S promoter showed constitutive phot2 responses, including chloroplast avoidance response, stomatal opening, and reduced hypocotyl phototropism regardless of blue light, and some detrimental growth phenotypes. In this study, to exclude the detrimental growth phenotypes caused by the ectopic expression of P2C and to improve leaf transpiration, we used the PHOT2 promoter for the endogenous expression of GFP-fused P2C (GP2C) (P2-GP2C) and the BLUS1 promoter for the guard-cell-specific expression of GP2C (B1-GP2C), respectively. In P2-GP2C plants, GP2C expression induced constitutive phototropin responses and a relatively dwarf phenotype as in 35-P2CG plants. In contrast, B1-GP2C plants showed the guard-cell-specific P2C expression that induced constitutive stomatal opening with normal phototropism, chloroplast movement, and growth phenotype. Interestingly, leaf transpiration was significantly improved in B1-GP2C plants compared to that in P2-GP2C plants and WT. Taken together, this transgenic approach could be applied to improve leaf transpiration in indoor plants. Full article

The photon flux in the green wavelength region is relatively enriched in shade and the photon flux in the blue region is selectively filtered. In sole source lighting environments, increasing the fraction of blue typically decreases stem elongation and leaf expansion, and smaller leaves reduce photon capture and yield. Photons in the green region reverse these blue reductions through the photoreceptor cryptochrome in Arabidopsis thaliana, but studies in other species have not consistently shown the benefits of photons in the green region on leaf expansion and growth. Spectral effects can interact with total photon flux. Here, we report the effect of the fraction of photons in the blue (10 to 30%) and green (0 to 50%) regions at photosynthetic photon flux densities of 200 and 500 µmol m⁻² s⁻¹ in lettuce, cucumber and tomato. As expected, increasing the fraction of photons in the blue region consistently decreased leaf area and dry mass. By contrast, large changes in the fraction of photons in the green region had minimal effects on leaf area and dry mass in lettuce and cucumber. Photons in the green region were more potent at a lower fraction of photons in the blue region. Photons in the green region increased stem and petiole length in cucumber and tomato, which is a classic shade avoidance response. These results suggest that high-light crop species might respond to the fraction of photons in the green region with either shade tolerance (leaf expansion) or shade avoidance (stem elongation). Full article