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Complementation of hy5 Phenotypes by HYH Transcripts Analyses of independent transgenic lines constitutively overexpressing altHYH or flHYH under control of the 35S promoter in a hy5 background. (A) Hypocotyl length. (B) Lateral root phenotypes of representative plantlets. (C) Root greening phenotypes of representative plants. (D) Primary root length. Plant age: (A and D) = 8 dag (days after germination); (B) = 13 dag; (C) = 30 dag. Error bars represent standard error of the mean.
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The Arabidopsis transcription factor HY5 controls light-induced gene expression downstream of photoreceptors and plays an important role in the switch of seedling shoots from dark-adapted to light-adapted development. In addition, HY5 has been implicated in plant hormone signaling, accounting for the accelerated root system growth phenotype of hy5...
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In this study, we used a cross-species network approach to uncover nitrogen-regulated network modules conserved across a model and a crop species. By translating gene "network knowledge" from the data-rich model Arabidopsis (Arabidopsis thaliana) to a crop (Oryza sativa), we identified evolutionarily conserved N-regulatory modules as targets for tr...
Citations
... Unequal genetic redundancy is a common phenomenon in Arabidopsis (Laubinger et al., 2004, Dohmann et al., 2005, Sibout et al., 2006and likely in crops and other models (Briggs et al., 2006). For example, MYC2 shows unequal genetic redundancy with a bZIP transcription factor GBF1 in regulating hypocotyl growth (Maurya et al., 2015). ...
... However, the spa1spa2 double mutants show shorter hypocotyls than the spa1, suggesting that SPA1 and SPA2 show unequal redundancy in controlling hypocotyl growth (Laubinger et al., 2004). Similarly, the two closely related bZIP transcription factors, which are key regulators of photomorphogenic growth, showed reduced root system growth phenotype in the hy5hyh double mutants than in the single mutants, wherein the root system growth is enhanced (Sibout et al., 2006). Consistent with the myc234 triple mutant phenotypes, such as long hypocotyl, reduced anthocyanin and chlorophyll accumulation, our results also revealed reduced HY5 protein stability in the myc234 triple mutants under WL and BL. ...
Light is one of the most critical ecological cues controlling plant growth and development. Plants have evolved complex mechanisms to cope with fluctuating light signals. In Arabidopsis, bHLH transcription factors MYC2, MYC3, and MYC4 have been shown to play a vital role in protecting plants against herbivory and necrotrophic pathogens. While the role of MYC2 in light-mediated seedling development has been studied in some detail, the role of MYC3 and MYC4 still needs to be discovered. Here, we show that MYC4 negatively regulates seedling photomorphogenesis, while the MYC3 function seems redundant. However, the genetic analysis reveals that MYC3/MYC4 together act as positive regulators of seedling photomorphogenic growth as the myc3myc4 double mutants showed exaggerated hypocotyl growth compared to myc4 single mutants and Col-0. Intriguingly, the loss of MYC2 function in the myc3myc4 double mutant background ( myc2myc3myc4 ) resulted in further enhancement in the hypocotyl growth than myc3myc4 double mutants in WL, BL and FRL, suggesting that MYC2/3/4 together play an essential and positive role in meditating optimal seedling photomorphogenesis. Besides, MYC3/MYC4 genetically and physically interact with HY5 to partially inhibit its function in controlling hypocotyl and photo-pigment accumulation. Moreover, our results suggest that COP1 physically interacts and degrades MYC3 and MYC4 through the 26S proteasomal pathway and controls their response to dark and light for fine-tuning HY5 function and seedling photomorphogenesis.
... To further explore the biological function of TaHY5-7A, we heterologously expressed TaHY5-7A in the Arabidopsis hy5 mutant and obtained three TaHY5-7A-overexpression (TaHY5-7A-OE) lines. This is because the hy5 mutant seedlings exhibited an elongated hypocotyl phenotype even when grown in the light and had defects in light-induced chlorophyll and anthocyanin accumulation [38,64,65]. Thus, we first assessed the hypocotyl elongation in the TaHY5-7A-OE lines. ...
... RT-qPCR revealed that TaHY5-7A had the highest expression among the HY5 genes in wheat in response to light (Figure 3a-f,j). Mutations in Arabidopsis HY5 caused defects in hypocotyl elongation and light-induced chlorophyll and anthocyanin accumulation [38,64,65]. However, the heterologous expression of TaHY5-7A partially rescued the hypocotyl growth and anthocyanin accumulation of the Arabidopsis hy5 mutant (Figure 5a-i). ...
Purple-grained wheat (Triticum aestivum L.) is an important germplasm source in crop breeding. Anthocyanin biosynthesis in the pericarps of purple-grained wheat is largely light-dependent; however, the regulatory mechanisms underlying light-induced anthocyanin accumulation in the wheat pericarp remain unknown. Here we determined that anthocyanins rapidly accumulate in the pericarps of the purple-grained wheat cultivar Heixiaomai 76 (H76) at 16 days after pollination under light treatment. Using transcriptome sequencing, differential gene expression analysis, and phylogenetic analysis, we identified two key genes involved in light signaling in wheat: ELONGATED HYPOCOTYL 5-7A (TaHY5-7A) and B-BOX-3B (TaBBX-3B). TaHY5-7A and TaBBX-3B were highly expressed in purple-grained wheat pericarps. The heterologous expression of TaHY5-7A partially restored the phenotype of the Arabidopsis (Arabidopsis thaliana) hy5 mutant, resulting in increased anthocyanin accumulation and a shortened hypocotyl. The heterologous expression of TaBBX-3B in wild-type Arabidopsis had similar effects. TaHY5-7A and TaBBX-3B were nucleus-localized, consistent with a function in transcription regulation. However, TaHY5-7A, which lacks a transactivation domain, was not sufficient to activate the expression of PURPLE PERICARP-MYB 1 (TaPpm1), the key anthocyanin biosynthesis regulator in purple pericarps of wheat. TaHY5-7A physically interacted with TaBBX-3B in yeast two-hybrid and bimolecular fluorescence complementation assays. Additionally, TaHY5-7A, together with TaBBX-3B, greatly enhanced the promoter activity of TaPpm1 in a dual luciferase assay. Overall, our results suggest that TaHY5-7A and TaBBX-3B collaboratively activate TaPpm1 expression to promote light-induced anthocyanin biosynthesis in purple-pericarp wheat.
... The transcription factor HY5, which is a key regulator of photomorphogenesis (Oyama et al., 1997), also has been linked to hormonal modulation. HY5 impacts GA (Alabadı́et al., 2008), auxin (Cluis et al., 2004;Sibout et al., 2006), and ABA (Chen et al., 2008) signaling. Recent studies have also linked G-box-specific binding transcription factor bZIP16 to light, GA, and ABA signaling through regulating the expression of genes including PIL5 and RGL2 (Hsieh et al., 2012). ...
The seed-to-seedling transition is impacted by changes in nutrient availability and light profiles, but is still poorly understood. Phenylalanine affects early seedling development; thus, the roles of arogenate dehydratases (ADTs), which catalyze phenylalanine formation, were studied in germination and during the seed-to-seedling transition by exploring the impact of light conditions and specific hormone responses in adt mutants of Arabidopsis thaliana . ADT gene expression was assessed in distinct tissues and for light-quality dependence in seedlings for each of the six-member ADT gene family. Mutant adt seedlings were evaluated relative to wild type for germination, photomorphogenesis (blue, red, far red, white light, and dark conditions), anthocyanin accumulation, and plastid development-related phenotypes. ADT proteins are expressed in a light- and tissue-specific manner in transgenic seedlings. Among the analyzed adt mutants, adt3 , adt5 , and adt6 exhibit significant defects in germination, hypocotyl elongation, and root development responses during the seed-to-seedling transition. Interestingly, adt5 exhibits a light-dependent disruption in plastid development, similar to a phyA mutant. These data indicate interactions between photoreceptors, hormones, and regulation of phenylalanine pools in the process of seedling establishment. ADT5 and ADT6 may play important roles in coordinating hormone and light signals for normal early seedling development.
... In the dark, COP1 E3 ligase directly interacts with HY5 and targets it for proteasome-mediated degradation. On the other hand, light exposure deactivates COP1 and triggers HY5 expression, resulting in HY5 protein production [62]. HY5 acts as a signal integration point in the light and hormone signaling networks [63]. ...
Light is a fundamental environmental parameter for plant growth and development because it provides an energy source for carbon fixation during photosynthesis and regulates many other physiological processes through its signaling. In indoor horticultural cultivation systems, sole-source light-emitting diodes (LEDs) have shown great potential for optimizing growth and producing high-quality products. Light is also a regulator of flowering, acting on phytochromes and inducing or inhibiting photoperiodic plants. Plants respond to light quality through several light receptors that can absorb light at different wavelengths. This review summarizes recent progress in our understanding of the role of blue and red light in the modulation of important plant quality traits, nutrient absorption and assimilation, as well as secondary metabolites, and includes the dynamic signaling networks that are orchestrated by blue and red wavelengths with a focus on transcriptional and metabolic reprogramming, plant productivity, and the nutritional quality of products. Moreover, it highlights future lines of research that should increase our knowledge to develop tailored light recipes to shape the plant characteristics and the nutritional and nutraceutical value of horticultural products.
... The hy5 hyh double mutant, which showed not root response to WL+FR treatment, was also less responsive to GA4 treatment, suggesting that GA4 response in roots involves HY5. GA4-shoot treatment led to an increase of HY5 in the root and HY5 is known to be able to repress auxin signaling in the root (Cluis et al., 2004;Sibout et al., 2006;van Gelderen et al., 2018), which was confirmed by the qPCR and ChIP-qPCR data after HY5 induction. Furthermore, the qPCR results showed that in the hy5 hyh mutant, the effect of GA4 application was modified: In hy5 hyh roots, GA4-shoot treatment led to an increase in auxin-related expression, indicating that HY5 normally represses this GA response. ...
Plants compete for light by growing taller than their nearest competitors. This is part of the shade avoidance syndrome and is a response to an increase of Far-Red light (FR) reflected from neighboring leaves. The root responds to this shoot-sensed FR cue by reducing lateral root emergence. It is well-established that the plant hormone Gibberellic Acid (GA) is involved in supplemental FR-induced shoot elongation. Although GA is also transported from shoot to root, its role in regulating lateral root growth is unclear. We show via GA manipulations, both chemical and genetic, that GA modulates the lateral root reduction induced by shoot-sensed FR enrichment. Using the FRET-based GA biosensor GPS1, we observed detailed GA changes in the root upon shoot exposure to FR enrichment and when GA was supplied to the shoot. Supplying GA to the shoot also mitigated the FR-enrichment root phenotype, indicating a functional link between GA and changes in root development in response to shoot-sensed FR. The regulatory role of GA in root growth appears to be partially dependent upon the role of ELONGATED HYPOCOTYL 5 (HY5), a light-responsive transcription factor that regulates root growth. Shoot-to-root transported GA4 led to an increase in HY5 protein levels in the lateral root primordia. HY5 then repressed auxin signaling to repress lateral root growth. Our data unveil a novel way in which hormone and light signaling coordinate development across spatial scales by adjusting (lateral) root growth from above-ground FR light signals.
... In general, HY5 activation in the root is eventually accomplished by either shoot to root translocation of HY5 or stem-piping light-activated phyB, which then activates HY5 (Lee et al. 2016). Activated HY5 further regulates the gravitropic or hydrotropic responses of the plant roots (Correll and Kiss 2005;Moriwaki et al. 2012;Oyama et al. 1997;Sibout et al. 2006;Yang et al. 2020). Although both light and ABA can induce MIZ1 expression, ABA-mediated MIZ1 regulation appears to be independent of light (Moriwaki et al. 2012). ...
Drought is one of the most critical stresses, which causes an enormous reduction in crop yield. Plants develop various strategies like drought escape, drought avoidance, and drought tolerance to cope with the reduced availability of water during drought. Plants adopt several morphological and biochemical modifications to fine-tune their water-use efficiency to alleviate drought stress. ABA accumulation and signaling plays a crucial role in the response of plants towards drought. Here, we discuss how drought-induced ABA regulates the modifications in stomatal dynamics, root system architecture, and the timing of senescence to counter drought stress. These physiological responses are also regulated by light, indicating the possibility of convergence of light- and drought-induced ABA signaling pathways. In this review, we provide an overview of investigations reporting light-ABA signaling cross talk in Arabidopsis as well as other crop species. We have also tried to describe the potential role of different light components and their respective photoreceptors and downstream factors like HY5, PIFs, BBXs, and COP1 in modulating drought stress responses. Finally, we highlight the possibilities of enhancing the plant drought resilience by fine-tuning light environment or its signaling components in the future.
... The mobile transcriptional factors TGACG-motif binding factor 3/4 (GmSTF3/4) and FLOWERING LOCUS T (GmFTs), which move from shoots to roots, activate nodulation events including upregulation of GmNIN, nuclear factor Y (GmNF-YA1 and NF-YB1) and GmENOD40 transcripts Li et al. 2022b). Soybean GmSTFs are orthologs of Arabidopsis HY5, which has been well characterized as a central regulator of light signaling, directly or indirectly controlling auxin transport and auxin signaling on a transcriptional level (Cluis et al. 2004;Sibout et al. 2006;van Gelderen et al. 2018). Thus, auxin regulation possibly also contributes to GmSTF-dependent soybean nodulation. ...
Breeding crop varieties with high yield and ideal plant architecture is a desirable goal of agricultural science. The success of “Green Revolution” in cereal crops provides opportunities to incorporate phytohormones in crop breeding. Auxin is a critical phytohormone to determine nearly all the aspects of plant development. Despite the current knowledge regarding auxin biosynthesis, auxin transport and auxin signaling have been well characterized in model Arabidopsis (Arabidopsis thaliana) plants, how auxin regulates crop architecture is far from being understood, and the introduction of auxin biology in crop breeding stays in the theoretical stage. Here, we give an overview on molecular mechanisms of auxin biology in Arabidopsis, and mainly summarize auxin contributions for crop plant development. Furthermore, we propose potential opportunities to integrate auxin biology in soybean (Glycine max) breeding.
... In this study, many MYB, bHLH, WRKY, and NAC family transcription factors were differentially expressed in both lotus varieties (Table S7). Among the transcription factors, HY5 forms heterodimers with many different classes of transcription factors, such as bZIPs, bHLHs, MYBs, and calmodulin, and regulates hypocotyl growth, lateral root growth, pigment accumulation, and the expression of lightinducible genes [74][75][76]. HY5 directly binds to either the G-box or ACE-box of MYB transcription factors, such as PRODUCTION OF FLAVONOL GLYCOSIDES (MYB12, MYB111, MYB113, and MYB114), PRODUCTION OF ANTHOCYANIN PIGMENT1 (MYB75), and MYB-like Domain (MYBD), to promote their expression [77,78]. MYB12 and MYB111 further bind to the promoters of early flavonoid biosynthetic genes such as chalcone synthase (CHS), chalcone isomerase (CHI), and flavanone 3-hydroxylase (F3H), whereas MYB75 binds to the promoters of late flavonoid biosynthetic genes such as DFR, LDOX, and UF3GT [77,79]. ...
Bowl lotus is categorized as a heliophyte, and shaded environments can severely retard its development and blossoming. We conducted a comparative omics study of light response difference between two cultivars, ‘HongYunDieYing’ (shade tolerant) and ‘YingYing’ (shade intolerant), to understand the mechanisms behind the shade tolerance response. The results indicated that ‘HongYunDieYing’ had a faster light signal response than that in ‘YingYing’. Furthermore, 214 proteins in ‘HongYunDieYing’ and 171 proteins in ‘YingYing’ were differentially expressed at both the transcriptional and protein levels. These correlated members were mainly involved in photosynthesis, metabolism, secondary metabolites, ribosome, and protein biosynthesis. However, glycolysis/gluconeogenesis, carbon metabolism, fatty acid metabolism, glutathione metabolism, and hormone signaling, were unique to ‘HongYunDieYing’. The molecular model of light signal regulation of shade tolerance was constructed: the upstream light signal transduction related gene (cryptochrome 1, phytohormone B, phytochrome-interacting factor 3/5, ELONGATED HYPOCOTYL 5, and SUPPRESSOR OF PHYA-1) played a decisive role in regulating shade tolerance traits. Some transcription factors (MYBs, bHLHs and WRKYs) and hormone signaling (auxin, gibberellin and ethylene) were involved in mediating light signaling to regulate downstream biological events. These regulators and biological processes synergistically regulated the shade tolerance of lotus.
Significance
Lotus requires sufficient sunlight for growth and development, and shaded environments will severely retard lotus growth and blossoming. At present, there are few reports on the systematic identification and characterization of light signal response-related regulators in lotus. This study focuses on the comparative analysis two bowl lotus cultivars with the different shade tolerance traits at transcriptome and proteome levels to uncover the novel insight of the light signal-related biological network and potential candidates involved in the mechanism. The results provide a theoretical basis for the bowl lotus breeding and the expansion of its applications.
... HYH is homologous to HY5 and indicated a light-induced expression pattern in our data (Fig. 5), initially opposite to HY5 (Fig. 5a). HY5 and HYH can act as heterodimers or homodimers and have overlapping or redundant functions, usually with HY5 being the more important homolog (57)(58)(59)(60)(61)(62). Of note, HYH expression had already increased by 6h after UV-B, but HY5 expression did so as well at later time points ( Fig. 5b) and less so by monochromatic than by broadband UV-B. ...
UV‐B as a component of natural solar radiation can induce damage as well as morphological development in plants. The UV‐B response from germination and early development in seedlings is still largely unknown, with most studies focused on older, light‐exposed seedlings. We used fluence response curves measuring hypocotyl length after UV‐B exposure coupled with RNA‐seq and sRNA‐seq evaluation of the early seedling response in the model organism Arabidopsis thaliana. We identified miR5642 as a potential novel key regulator of UV‐B responses. MiR5642 is a non‐canonical miRNA predicted to target previously known and unknown components involved in hypocotyl growth inhibition. These include (i) SMAX1, a signal transmitter for seedling germination and growth, (ii) ZAT1, an uncharacterized transcription factor, and (iii) membrane pores and transporters (VHA‐E1, VHA‐E3, EPSIN‐LIKE, PIP1.4) implicated in cell elongation. In addition, HY5 and HYH, two homologous and redundant transcription factors involved in seedling photomorphogenesis, may interact with these newly identified components. Interestingly, UV‐B‐induced DNA photodimer formation seems to be the direct trigger leading to inhibition of hypocotyl growth through a combination of cellular decisions including cell cycle arrest, reduced endoreduplication, and reduced cell elongation, and this inhibition appears to be modulated by miR5642 target genes.
... HY5 and its homolog HYH were detected as significantly downregulated in max2 in comparison to WT roots under mock conditions, although this result could not be validated by the qRT-PCR analysis. HY5 has been previously reported to increase the flavonol content in the roots by transcriptional activation of several flavonoid biosynthesis genes (Sibout et al. 2006, Stracke et al. 2010b, Shin et al. 2013, Zhang et al. 2019). Here, we show that HY5 is also essential for the rac-GR24-dependent flavonol readout and MYB12 expression, just like MAX2, in agreement with previous studies suggesting that MYB12 is under HY5 control in the root (Stracke et al. 2010b). ...
The synthetic strigolactone (SL) analog, rac-GR24, has been instrumental in studying the role of SLs as well as karrikins because it activates the receptors DWARF14 (D14) and KARRIKIN INSENSITIVE 2 (KAI2) of their signaling pathways, respectively. Treatment with rac-GR24 modifies the root architecture at different levels, such as decreasing the lateral root density (LRD), while promoting root hair elongation or flavonol accumulation. Previously, we have shown that the flavonol biosynthesis is transcriptionally activated in the root by rac-GR24 treatment, but, thus far, the molecular players involved in that response have remained unknown. To get an in-depth insight into the changes that occur after the compound is perceived by the roots, we compared the root transcriptomes of the wild type and the more axillary growth2 (max2) mutant, affected in both SL and karrikin signaling pathways, with and without rac-GR24 treatment. Quantitative reverse transcription (qRT)-PCR, reporter line analysis and mutant phenotyping indicated that the flavonol response and the root hair elongation are controlled by the ELONGATED HYPOCOTYL 5 (HY5) and MYB12 transcription factors, but HY5, in contrast to MYB12, affects the LRD as well. Furthermore, we identified the transcription factors TARGET OF MONOPTEROS 5 (TMO5) and TMO5 LIKE1 as negative and the Mediator complex as positive regulators of the rac-GR24 effect on LRD. Altogether, hereby, we get closer toward understanding the molecular mechanisms that underlay the rac-GR24 responses in the root.
