Liquid-liquid phase separation of TZP promotes PPK-mediated phosphorylation of the phytochrome A photoreceptor.

Phytochrome A (phyA) is the plant far-red (FR) light photoreceptor and plays an essential role in regulating photomorphogenic development in FR-rich conditions, such as canopy shade. It has long been observed that phyA is a phosphoprotein in vivo; however, the protein kinases that could phosphorylate phyA remain largely unknown. Here we show that a small protein kinase family, consisting of four members named PHOTOREGULATORY PROTEIN KINASES (PPKs) (also known as MUT9-LIKE KINASES), directly phosphorylate phyA in vitro and in vivo. In addition, TANDEM ZINC-FINGER/PLUS3 (TZP), a recently characterized phyA-interacting protein required for in vivo phosphorylation of phyA, is also directly phosphorylated by PPKs. We reveal that TZP contains two intrinsically disordered regions in its amino-terminal domain that undergo liquid-liquid phase separation (LLPS) upon light exposure. The LLPS of TZP promotes colocalization and interaction between PPKs and phyA, thus facilitating PPK-mediated phosphorylation of phyA in FR light. Our study identifies PPKs as a class of protein kinases mediating the phosphorylation of phyA and demonstrates that the LLPS of TZP contributes significantly to more production of the phosphorylated phyA form in FR light.

Assessing the Function of CBF1 in Modulating the Interaction Between Phytochrome B and PIF4.

Phytochromes are red (R) and far-red (FR) light photoreceptors in plants. Upon light exposure, photoactivated phytochromes translocate into the nucleus, where they interact with their partner proteins to transduce light signals. The yeast two-hybrid (Y2H) system is a powerful technique for rapidly identifying and verifying protein-protein interactions, and PHYTOCHROME-INTERACTING FACTOR3 (PIF3), the founding member of the PIF proteins, was initially identified in a Y2H screen for phytochrome B (phyB)-interacting proteins. Recently, we developed a yeast three-hybrid (Y3H) system by introducing an additional vector into this Y2H system, and thus a new regulator could be co-expressed and its role in modulating the interactions between phytochromes and their signaling partners could be examined. By employing this Y3H system, we recently showed that both MYB30 and CBF1, two negative regulators of seedlings photomorphogenesis, act to inhibit the interactions between phyB and PIF4/PIF5. In this chapter, we will use the CBF1-phyB-PIF4 module as an example and describe the detailed procedure for performing this Y3H assay. It will be intriguing and exciting to explore the potential usage of this Y3H system in future research.

Molecular mechanisms underlying coordinated responses of plants to shade and environmental stresses.

Shade avoidance syndrome (SAS) is triggered by a low ratio of red (R) to far-red (FR) light (R/FR ratio), which is caused by neighbor detection and/or canopy shade. In order to compete for the limited light, plants elongate hypocotyls and petioles by deactivating phytochrome B (phyB), a major R light photoreceptor, thus releasing its inhibition of the growth-promoting transcription factors PHYTOCHROME-INTERACTING FACTORs. Under natural conditions, plants must cope with abiotic stresses such as drought, soil salinity, and extreme temperatures, and biotic stresses such as pathogens and pests. Plants have evolved sophisticated mechanisms to simultaneously deal with multiple environmental stresses. In this review, we will summarize recent major advances in our understanding of how plants coordinately respond to shade and environmental stresses, and will also discuss the important questions for future research. A deep understanding of how plants synergistically respond to shade together with abiotic and biotic stresses will facilitate the design and breeding of new crop varieties with enhanced tolerance to high-density planting and environmental stresses.

Neoadjuvant chemoimmunotherapy cycle number selection for non-small cell lung cancer and clinical outcomes: a real-world analysis.

Objectives: Neoadjuvant chemoimmunotherapy is the optimal choice in the treatment of NSCLC; however, the optimal number of therapeutic cycles remains unclear. The primary aim of this study was to determine the optimal number of neoadjuvant therapeutic cycles in NSCLC. Methods: This study was a real-world clinical analysis that included patients who received neoadjuvant chemoimmunotherapy followed by surgery from January 2020 to August 2022. Patients were divided into two groups based on the number of therapeutic cycles: 2-cycle group and 3-4-cycles group. The primary endpoint was the major pathological response (MPR) rate. Results: A total of 251 patients were included: 150 in the 2-cycle group and 101 in the 3-4-cycles group. Baseline characteristics were well-balanced between the groups. The MPR in the 2-cycle group was 57.3% and not significantly different from that of 57.4% in the 3-4-cycles group (p=0.529). Thirty-two patients (31.7%) in the 3-4-cycles group underwent surgery > 42 days after the final cycle of neoadjuvant therapy, significantly more than the 24 patients (16.0%) in the 2-cycle group (p=0.003). The incidence of adverse events related to neoadjuvant therapy was higher in the 3-4-cycles vs 2-cycle groups (72.3% versus 58.0%, respectively; p=0.021), while the 2-cycle group had a higher rate of postoperative morbidities (28.0% versus 12.9%, respectively; p=0.004). Additionally, for patients with ≤ 44.2% regression in diameter on computed tomography after two cycles of treatment, the MPR rate was higher in the 3-4-cycles vs 2-cycle group (47.3% versus 29.9%, respectively; p=0.048). For cases with programmed death-ligand 1 expression, regarding tumor proportion score ≤ 10%, 3-4 cycles of neoadjuvant treatment increased the MPR rate compared with 2 cycles (37.5% versus 9.5%, respectively; p=0.041). Conclusion: Our data support the positive role of chemoimmunotherapy in the neoadjuvant treatment of NSCLC. Extending to 3-4 cycles instead of 2 cycles of neoadjuvant chemoimmunotherapy may improve the safety of surgery and result in a lower incidence of postoperative morbidities; however, the MPR rate may not increase significantly. CT re-evaluation during treatment and PD-L1 expression at initial diagnosis are potential indicators to guide the choice of the number of therapeutic cycles.

Reconstitution of phytochrome A-mediated light modulation of the ABA signaling pathways in yeast.

Abscisic acid (ABA), a classical plant hormone, plays an essential role in plant adaptation to environmental stresses. The ABA signaling mechanisms have been extensively investigated, and it was shown that the PYR1 (PYRABACTIN RESISTANCE1)/PYL (PYR1-LIKE)/RCAR (REGULATORY COMPONENT OF ABA RECEPTOR) ABA receptors, the PP2C coreceptors, and the SnRK2 protein kinases constitute the core ABA signaling module responsible for ABA perception and initiation of downstream responses. We recently showed that ABA signaling is modulated by light signals, but the underlying molecular mechanisms remain largely obscure. In this study, we established a system in yeast cells that was not only successful in reconstituting a complete ABA signaling pathway, from hormone perception to ABA-responsive gene expression, but also suitable for functionally characterizing the regulatory roles of additional factors of ABA signaling. Using this system, we analyzed the roles of several light signaling components, including the red and far-red light photoreceptors phytochrome A (phyA) and phyB, and the photomorphogenic central repressor COP1, in the regulation of ABA signaling. Our results showed that both phyA and phyB negatively regulated ABA signaling, whereas COP1 positively regulated ABA signaling in yeast cells. Further analyses showed that photoactivated phyA interacted with the ABA coreceptors ABI1 and ABI2 to decrease their interactions with the ABA receptor PYR1. Together, data from our reconstituted yeast ABA signaling system provide evidence that photoactivated photoreceptors attenuate ABA signaling by directly interacting with the key components of the core ABA signaling module, thus conferring enhanced ABA tolerance to light-grown plants.

Challenging routine: technical difficulties and solutions of endoscopic thyroidectomy via a combined transoral and breast approach - a case-series and learning curve.

OBJECTIVE: Conventional cervical lymph node dissection often leaves large surgical scars, which seriously compromises the postoperative aesthetic effect and can affect the quality of life of patients. In this study, the safety and feasibility of robotic-assisted endoscopic thyroidectomy with central neck dissection (CND) and lateral neck dissection (LND) via a combined transoral and breast approach are discussed in detail. MATERIALS AND METHODS: A retrospective analysis was made of the data of 26 patients with stage cN1b papillary thyroid carcinoma who were admitted to the Thyroid Surgery Department of the Hunan Cancer Hospital from March 2021 to September 2022 and who underwent robotic-assisted endoscopic thyroidectomy with LND via a combined transoral and breast approach. The demographic data, surgical indicators, postoperative data, and the postoperative complication rate of the patients were analyzed, and the learning curve was analyzed by cumulative summation. RESULTS: All the patients underwent endoscopic surgery without any conversion to open surgery. The mean operation time was 313.7±50.3 min and the mean number of total positive/retrieved lymph nodes was 11.2±8.1/36.8±13.7. Two patients developed temporary laryngeal recurrent nerve palsy and three patients developed temporary hypoparathyroidism, all of whom recovered within 3 months postoperatively. No tumor recurrence occurred during follow-ups that ranged from 6 to 24 months. The mean postoperative quality of life (QOL) score was 189.1±118.2, test results ranging from 0 to 1300 with a lower score indicating a higher QOL, and the aesthetic satisfaction score was 4.2±0.7, test scores ranging from 0 to 5 with higher scores indicate higher satisfaction. The turning point of the learning curve was in the 11th case. CONCLUSIONS: The robotic-assisted endoscopic thyroidectomy with CND and LND via a combined transoral and breast approach is safe and feasible, and the improved cosmetic effect is remarkable, which is conducive to improving the postoperative QOL of patients. It provides a new surgical option for patients.

Numerical analyses of seed morphology and its taxonomic significance in the genus Oxytropis DC. (Fabaceae) from northwestern China.

The lack of diagnostic taxonomic characteristics in some species complexes leave the species delimitation of Oxytropis DC. unresolved. Seed morphological features have proved to be useful diagnostic and taxonomic characteristics in Fabaceae. However, there are few systematic studies on the seed characteristics of Oxytropis. Here, we used scanning electron and stereoscopic microscopy to investigate the seed characteristics of 35 samples obtained from 21 Oxytropis species from northwest China. Our examination showed two main types of hilum positions, terminal and central, and five different types of seed shapes: prolonged semielliptic, reniform, prolonged reniform, quadratic, and cardiform. Seven different sculpturing patterns were identified: scaled, regulated, lophate with stellated testa cells, simple reticulate, rough, compound reticulate, and lophate with rounded testa cells. The seeds ranged from 1.27 to 2.57 mm in length and from 1.18 to 2.02 mm in width, and the length-to-width ratio ranged from 0.89 to 1.55 mm. The seed shape was constant within species and was useful for species delimitation within the genus Oxytropis when combined with other macroscopic traits. In contrast, the sculpturing patterns were highly variable at the species level and could not be used for species identification. Results of the cluster analysis and principal component analysis (PCA) indicated that the seed traits of Oxytropis species are useful for taxa identification at the species level, but have low taxonomic value at the section level.

Phytochromes enhance SOS2-mediated PIF1 and PIF3 phosphorylation and degradation to promote Arabidopsis salt tolerance.

Soil salinity is one of the most detrimental abiotic stresses affecting plant survival, and light is a core environmental signal regulating plant growth and responses to abiotic stress. However, how light modulates the plant's response to salt stress remains largely obscure. Here, we show that Arabidopsis (Arabidopsis thaliana) seedlings are more tolerant to salt stress in the light than in the dark, and that the photoreceptors phytochrome A (phyA) and phyB are involved in this tolerance mechanism. We further show that phyA and phyB physically interact with the salt tolerance regulator SALT OVERLY SENSITIVE2 (SOS2) in the cytosol and nucleus, and enhance salt-activated SOS2 kinase activity in the light. Moreover, SOS2 directly interacts with and phosphorylates PHYTOCHROME-INTERACTING FACTORS PIF1 and PIF3 in the nucleus. Accordingly, PIFs act as negative regulators of plant salt tolerance, and SOS2 phosphorylation of PIF1 and PIF3 decreases their stability and relieves their repressive effect on plant salt tolerance in both light and dark conditions. Together, our study demonstrates that photoactivated phyA and phyB promote plant salt tolerance by increasing SOS2-mediated phosphorylation and degradation of PIF1 and PIF3, thus broadening our understanding of how plants adapt to salt stress according to their dynamic light environment.

SALT OVERLY SENSITIVE2 stabilizes phytochrome-interacting factors PIF4 and PIF5 to promote Arabidopsis shade avoidance.

Sun-loving plants trigger the shade avoidance syndrome (SAS) to compete against their neighbors for sunlight. Phytochromes are plant red (R) and far-red (FR) light photoreceptors that play a major role in perceiving the shading signals and triggering SAS. Shade induces a reduction in the level of active phytochrome B (phyB), thus increasing the abundance of PHYTOCHROME-INTERACTING FACTORS (PIFs), a group of growth-promoting transcription factors. However, whether other factors are involved in modulating PIF activity in the shade remains largely obscure. Here, we show that SALT OVERLY SENSITIVE2 (SOS2), a protein kinase essential for salt tolerance, positively regulates SAS in Arabidopsis thaliana. SOS2 directly phosphorylates PIF4 and PIF5 at a serine residue close to their conserved motif for binding to active phyB. This phosphorylation thus decreases their interaction with phyB and posttranslationally promotes PIF4 and PIF5 protein accumulation. Notably, the role of SOS2 in regulating PIF4 and PIF5 protein abundance and SAS is more prominent under salt stress. Moreover, phyA and phyB physically interact with SOS2 and promote SOS2 kinase activity in the light. Collectively, our study uncovers an unexpected role of salt-activated SOS2 in promoting SAS by modulating the phyB-PIF module, providing insight into the coordinated response of plants to salt stress and shade.

Perioperative outcomes of neoadjuvant chemotherapy plus camrelizumab compared with chemotherapy alone and chemoradiotherapy for locally advanced esophageal squamous cell cancer.

Purpose: Neoadjuvant chemoimmunotherapy (nCIT) is becoming a new therapeutic frontier for resectable esophageal squamous cell carcinoma (ESCC); however, crucial details and technical know-how regarding surgical techniques and the perioperative challenges following nCIT remain poorly understood. The study investigated and compared the advantages and disadvantages of esophagectomy following nCIT with neoadjuvant chemotherapy (nCT) and chemoradiotherapy (nCRT). Methods: We retrospectively analyzed data of patients initially diagnosed with resectable ESCC at clinical stage T2-4N+ and received neoadjuvant therapy followed by esophagectomy at the Hunan Cancer Hospital between October 2014 and February 2021. Patients were divided into three groups according to neoadjuvant treatment: (i) nCIT; (ii) nCT; and (iii) nCRT. Results: There were 34 patients in the nCIT group, 97 in the nCT group, and 31 in the nCRT group. Compared with nCT, nCIT followed by esophagectomy achieved higher pathological complete response (pCR; 29.0% versus 4.1%, p<0.001) and major pathological response (MPR; 52.9% versus 16.5%, p<0.001) rates, more resected lymph nodes during surgery (25.06 ± 7.62 versus 20.64 ± 9.68, p=0.009), less intraoperative blood loss (200.00 ± 73.86 versus 266.49 ± 176.29 mL, p=0.035), and comparable results in other perioperative parameters. Compared with nCRT, nCIT achieved similar pCR (29.0% versus 25.8%) and MPR (52.9% versus 51.6%, p=0.862) rates, with significantly more lymph nodes resected during surgery (25.06 ± 7.62 versus 16.94 ± 7.24, p<0.001), shorter operation time (267.79 ± 50.67 versus 306.32 ± 79.92 min, p=0.022), less intraoperative blood loss (200.00 ± 73.86 versus 264.53 ± 139.76 mL, p=0.022), and fewer ICU admissions after surgery (29.4% versus 80.6%, p<0.001). Regarding perioperative adverse events and complications, no significant statistical differences were detected between the nCIT and the nCT or nCRT groups. The 3-year overall survival rate after nCIT was 73.3%, slightly higher than 46.1% after nCT and 39.7% after nCRT, with no statistically significant differences (p=0.883). Conclusions: This clinical analysis showed that nCIT is safe and feasible, with satisfactory pCR and MPR rates. Esophagectomy following nCIT has several perioperative advantages over nCT and nCRT, with comparable perioperative morbidity and mortality. The long-term survival benefits after nCIT still requires further investigation.

Purification and biochemical characterization of a novel ene- reductase from Kazachstania exigua HSC6 for dihydro-ß-ionone from ß-ionone.

PURPOSE: We purified and characterized a novel ene-reductase (KaDBR1) from Kazachstania exigua HSC6 for the synthesis of dihydro-ß-ionone from ß-ionone. METHODS: KaDBR1 was purified to homogeneity by ammonium sulfate precipitation and phenyl-Sepharose Fast Flow and Q-Sepharose chromatography. The purified enzyme was characterized by measuring the amount of dihydro-ß-ionone from ß-ionone with LC-MS analysis method. RESULTS: The molecular mass of KaDBR1 was estimated to be 45 kDa by SDS-PAGE. The purified KaDBR1 enzyme had optimal activity at 60 °C and pH 6.0. The addition of 5 mM Mg2+, Ca2+, Al3+, Na+, and dithiothreitol increased the activity of KaDBR1 by 25%, 18%, 34%, 20%, and 23%, respectively. KaDBR1 favored NADH over NADPH as a cofactor, and its catalytic efficiency (kcat/Km) toward ß-ionone using NADH was 8.1-fold greater than when using NADPH. CONCLUSION: Owing to its unique properties, KaDBR1 is a potential candidate for the enzymatic biotransformation of ß-ionone to dihydro-ß-ionone in biotechnology applications.

14-3-3 proteins regulate photomorphogenesis by facilitating light-induced degradation of PIF3.

14-3-3s are highly conserved phosphopeptide-binding proteins that play important roles in various developmental and signaling pathways in plants. However, although protein phosphorylation has been proven to be a key mechanism for regulating many pivotal components of the light signaling pathway, the role of 14-3-3 proteins in photomorphogenesis remains largely obscure. PHYTOCHROME-INTERACTING FACTOR3 (PIF3) is an extensively studied transcription factor repressing photomorphogenesis, and it is well-established that upon red (R) light exposure, photo-activated phytochrome B (phyB) interacts with PIF3 and induces its rapid phosphorylation and degradation. PHOTOREGULATORY PROTEIN KINASES (PPKs), a family of nuclear protein kinases, interact with phyB and PIF3 in R light and mediate multisite phosphorylation of PIF3 in vivo. Here, we report that two members of the 14-3-3 protein family, 14-3-3λ and κ, bind to a serine residue in the bHLH domain of PIF3 that can be phosphorylated by PPKs, and act as key positive regulators of R light-induced photomorphogenesis. Moreover, 14-3-3λ and κ preferentially interact with photo-activated phyB and promote the phyB-PIF3-PPK complex formation, thereby facilitating phyB-induced phosphorylation and degradation of PIF3 upon R light exposure. Together, our data demonstrate that 14-3-3λ and κ work in close concert with the phyB-PIF3 module to regulate light signaling in Arabidopsis.

Novel and multifaceted regulations of photoperiodic flowering by phytochrome A in soybean.

Photoperiod is an important environmental cue. Plants can distinguish the seasons and flower at the right time through sensing the photoperiod. Soybean is a sensitive short-day crop, and the timing of flowering varies greatly at different latitudes, thus affecting yields. Soybean cultivars in high latitudes adapt to the long day by the impairment of two phytochrome genes, PHYA3 and PHYA2, and the legume-specific flowering suppressor, E1. However, the regulating mechanism underlying phyA and E1 in soybean remains largely unknown. Here, we classified the regulation of the E1 family by phyA2 and phyA3 at the transcriptional and posttranscriptional levels, revealing that phyA2 and phyA3 regulate E1 by directly binding to LUX proteins, the critical component of the evening complex, to regulate the stability of LUX proteins. In addition, phyA2 and phyA3 can also directly associate with E1 and its homologs to stabilize the E1 proteins. Therefore, phyA homologs control the core flowering suppressor E1 at both the transcriptional and posttranscriptional levels, to double ensure the E1 activity. Thus, our results disclose a photoperiod flowering mechanism in plants by which the phytochrome A regulates LUX and E1 activity.

TIPE1 inhibits osteosarcoma tumorigenesis and progression by regulating PRMT1 mediated STAT3 arginine methylation.

Osteosarcoma (OS), the most common primary malignancy of the bone, has a poor prognosis due to its high mortality rate and high potential for metastasis. Thus, it is urgently necessary to explore functional molecular targets of therapeutic strategies for osteosarcoma. Here, we reported that TIPE1 expression was decreased in osteosarcoma tissues compared to normal and adjacent nontumor tissues, and its expression was negatively related to tumor stage and tumor size. Functional assays showed that TIPE1 inhibited osteosarcoma carcinogenesis and metastatic potential both in vivo and in vitro. Furthermore, we investigated that the STAT3 signaling pathway was significantly downregulated after TIPE1 overexpression. Mechanistically, TIPE1 bind to the catalytic domain of PRMT1, which deposits an asymmetric dimethylarginine (ADMA) mark on histone/non-histone proteins, and thus inhibited PRMT1 mediated STAT3 methylation at arginine (R) residue 688. This abolished modification decreased STAT3 transactivation and expression, by which subsequently suppressed osteosarcoma malignancy. Taken together, these data showed that TIPE1 inhibits the malignant transformation of osteosarcoma through PRMT1-mediated STAT3 arginine methylation and ultimately decreases the development and metastasis of osteosarcoma. TIPE1 might be a potential molecular therapeutic target and an early biomarker for osteosarcoma diagnosis.

Delayed complications of intradural cement leakage after percutaneous vertebroplasty: A case report.

BACKGROUND: Intradural cement leakage following percutaneous vertebroplasty is a rare but acute and devastating complication that usually requires emergent treatment. Here, we report a delayed complication of intradural leakage after percutaneous vertebroplasty. CASE SUMMARY: A 71-year-old female patient with an L1 osteoporotic compression fracture underwent percutaneous vertebroplasty in 2014. She was referred to our hospital 5 years later due to complaints of progressive weakness and numbness in both legs combined with urinary incontinence and constipation. Initially, she was suspected to have a spinal meningioma at the level of L1 according to imaging examinations. Postoperative pathological tests confirmed that cement had leaked into the dura during the first percutaneous vertebroplasty. CONCLUSION: Guideline adherence is essential to prevent cement from leaking into the spinal canal or even the dura. Once leakage occurs, urgent evaluation and decompression surgery are necessary to prevent further neurological damage.

NAD+ and its possible role in gut microbiota: Insights on the mechanisms by which gut microbes influence host metabolism.

Nicotinamide adenine dinucleotide (NAD+) is an enzyme cofactor, co-substrate, and redox factor in all living cells and is necessary for maintaining cell metabolism. It has been shown that appropriate supplementation of NAD+ precursors or inhibition of NAD+-depleting enzymes can promote mitochondrial oxidative phosphorylation and improve host energy utilization efficiency. In addition, increasing evidence indicates that the gut microbiota plays a pivotal role in host metabolism. Theoretically, there should be a close correlation among NAD+, gut microbiota, and host metabolism; however, the information is limited. In this review, we summarize the metabolic process of NAD+ and its impact on host metabolism, the link between gut microbiota and host metabolism, as well as the potential effects of NAD+ on microbial metabolism, providing a new perspective on the interaction between gut microbiota and host metabolism.

Facile and General Method to Synthesize Pt-Based High-Entropy-Alloy Nanoparticles.

Pt-based high-entropy-alloy nanoparticles (HEA-NPs) have excellent physical and chemical properties due to the diversity of composition, complexity of surface structure, high mixing entropy, and properties of nanoscale, and they are used in a wide range of catalytic applications such as catalytic ammoxidation, the electrolysis of water to produce hydrogen, CO2/CO reduction, and ethanol/methanol oxidation reaction. However, offering a facile, low-cost, and large-scale method for preparing Pt-based HEA-NPs still faces great challenges. In this study, we employed a spray drying technique combined with thermal decomposition reduction (SD-TDR) method to synthesize a single-phase solid solution from binary nanoparticles to denary Pt-based HEA-NPs containing 10 dissimilar elements loaded on carbon supports in an H2 atmosphere with a moderate heating rate (3 °C/min), thermal decomposition temperature (300-850 °C), duration time (30 min), and low cooling rate (5-10 °C/min). The Pt autocatalytic behavior was found and investigated, confirming that Pt element could decrease the reduction temperature of other metals via autocatalytic behavior. Therefore, using the feature of Pt autocatalytic behavior, we have achieved Pt-based HEA-NPs at a minimum temperature of 300 °C. We not only prepared a series of Pt-based HEA-NPs with targetable ingredient, size, and phase using the SD-TDR method but also proved the expandability of the SD-TDR technique by synthesizing Pt-based HEA-NPs loaded on different supports. Moreover, we investigated methanol oxidation reaction (MOR) on as-synthesized senary PtCoCuRuFeNi HEA-NPs, which presented superior electrocatalytic performance over commercial Pt/C catalyst.

SICKLE represses photomorphogenic development of Arabidopsis seedlings via HY5- and PIF4-mediated signaling.

Arabidopsis CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1) and PHYTOCHROME INTERACTING FACTORs (PIFs) are negative regulators, and ELONGATED HYPOCOTYL5 (HY5) is a positive regulator of seedling photomorphogenic development. Here, we report that SICKLE (SIC), a proline rich protein, acts as a novel negative regulator of photomorphogenesis. HY5 directly binds the SIC promoter and activates SIC expression in response to light. In turn, SIC physically interacts with HY5 and interferes with its transcriptional regulation of downstream target genes. Moreover, SIC interacts with PIF4 and promotes PIF4-activated transcription of itself. Interestingly, SIC is targeted by COP1 for 26S proteasome-mediated degradation in the dark. Collectively, our data demonstrate that light-induced SIC functions as a brake to prevent exaggerated light response via mediating HY5 and PIF4 signaling, and its degradation by COP1 in the dark avoid too strong inhibition on photomorphogenesis at the beginning of light exposure.

Transcriptomic comparison sheds new light on regulatory networks for dimorphic flower development in response to photoperiod in Viola prionantha.

BACKGROUND: Chasmogamous (CH)-cleistogamous (CL) dimorphic flowers are developed in Viola prionantha. However, the environmental and genetic factors necessary for the CH-CL transition are unknown. RESULTS: In the present work, short-day (SD) conditions induced CH flowers, whereas long days (LDs) triggered CL flowers in V. prionantha. Compared to fully developed CH flowers, CL flowers had less mature stamens, no nectar glands, and immature petals. Comparative transcriptomics revealed differentially expressed genes (DEGs) during CL and CH development. Core genes in the photoperiod pathway, such as V. prionantha orthologs of GIGANTEA (GI), CONSTANS (CO), and SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1), which promote floral induction, were highly expressed in CL flowers, whereas UNUSUAL FLORAL ORGANS (UFO) and B-class MADS-box genes for floral organ identity and development showed an opposite alteration. Moreover, genes in the glycolytic process, sucrose metabolic process, and fatty acid biosynthetic process were all highly expressed in CH flowers. Interestingly, V. prionantha orthologs of the B-class MADS-box genes APETALA3 (AP3) and PISTILLATA (PI) might relate to these sugar-fatty acid processes and were co-expressed with GAIP-B-like and YABBY5 (YAB5), which regulate the development of the petal, stamen, and nectary. Compared to CH flowers, DEGs and hub genes in the most significantly correlated modules of the gene co-expression network, which are involved in abiotic and biotic responses, were upregulated in CL flowers. CONCLUSIONS: We proposed an integrative model for transcription regulation of genes in the photoperiod pathway, floral organ development, stress response, and sugar-fatty acid processes to determine CH-CL flower development in V. prionantha. Particularly, under LDs, activated GI may induce genes involved in the stress-response pathways, and then downregulated AP3 and PI or UFO to inhibit the sugar-fatty acid metabolic processes, together forming CL flowers. In contrast, CH flowers were produced under SDs. This work provides novel insights into the developmental evolution of dimorphic flowers in Viola.