TT3.1: a journey to protect chloroplasts upon heat stress

Rice (Oryza sativa L.) is a staple crop that feeds over half the world's population. High temperature stress is a great threaten to sustainable agriculture and leads to yield loss and impaired grain quality in major crops. Rice is sensitive to heat stress at almost all the growth stages and the molecular mechanisms underlying responses to heat stress in rice is emerging. Through quantitative trait locus (QTL) mapping, a recent study conducted by Zhang et al. shows that one genetic locus Thermo-tolerance 3 (TT3) contains two genes that are required for thermotolerance in rice. The TT3.1-TT3.2 genetic module in rice links the plasma membrane to chloroplasts to protect chloroplasts from heat stress damage and increases grain yield under heat stress conditions. This breakthrough provides a promising strategy for future breeding of high temperature resilient crops.

REVEILLE 7 inhibits the expression of the circadian clock gene EARLY FLOWERING 4 to fine-tune hypocotyl growth in response to warm temperatures

The circadian clock maintains the daily rhythms of plant growth and anticipates predictable ambient temperature cycles. The evening complex (EC), comprising EARLY FLOWERING 3 (ELF3), ELF4, and LUX ARRHYTHMO, plays an essential role in suppressing thermoresponsive hypocotyl growth by negatively regulating PHYTOCHROME INTERACTING FACTOR 4 (PIF4) activity and its downstream targets in Arabidopsis thaliana. However, how EC activity is attenuated by warm temperatures remains unclear. Here, we demonstrate that warm temperature-induced REVEILLE 7 (RVE7) fine-tunes thermoresponsive growth in Arabidopsis by repressing ELF4 expression. RVE7 transcript and RVE7 protein levels increased in response to warm temperatures. Under warm temperature conditions, an rve7 loss-of-function mutant had shorter hypocotyls, while overexpressing RVE7 promoted hypocotyl elongation. PIF4 accumulation and downstream transcriptional effects were reduced in the rve7 mutant but enhanced in RVE7 overexpression plants under warm conditions. RVE7 associates with the Evening Element in the ELF4 promoter and directly represses its transcription. ELF4 is epistatic to RVE7, and overexpressing ELF4 suppressed the phenotype of the RVE7 overexpression line under warm temperature conditions. Together, our results identify RVE7 as an important regulator of thermoresponsive growth that functions (in part) by controlling ELF4 transcription, highlighting the importance of ELF4 for thermomorphogenesis in plants.

UBA domain protein SUF1 interacts with NatA-complex subunit NAA15 to regulate thermotolerance in Arabidopsis

During recovery from heat stress, plants clear away the heat-stress-induced misfolded proteins through the ubiquitin-proteasome system (UPS). In the UPS, the recognition of substrate proteins by E3 ligase can be regulated by the N-terminal acetyltransferase A (NatA) complex. Here, we determined that Arabidopsis STRESS-RELATED UBIQUITIN-ASSOCIATED-DOMAIN PROTEIN FACTOR 1 (SUF1) interacts with the NatA complex core subunit NAA15 and positively regulates NAA15. The suf1 and naa15 mutants are sensitive to heat stress; the NatA substrate ^N SNC1 is stabilized in suf1 mutant plants during heat stress recovery. Therefore, SUF1 and its interactor NAA15 play important roles in basal thermotolerance in Arabidopsis.

Regulation of Chloroplast Development and Function at Adverse Temperatures in Plants

The chloroplast is essential for photosynthesis, plant growth and development. As semiautonomous organelles, the biogenesis and development of chloroplasts need to be well-regulated during plant growth and stress responses. Low or high ambient temperatures are adverse environmental stresses that affect crop growth and productivity. As sessile organisms, plants regulate the development and function of chloroplasts in a fluctuating temperature environment to maintain normal photosynthesis. This review focuses on the molecular mechanisms and regulatory factors required for chloroplast biogenesis and development under cold or heat stress conditions and highlights the importance of chloroplast gene transcription, RNA metabolism, ribosome function and protein homeostasis essential for chloroplast development under adverse temperature conditions.

bZIP17 regulates heat stress tolerance at reproductive stage in Arabidopsis

High temperature elicits a well-conserved response called the unfolded protein response (UPR) to bring protein homeostasis in the endoplasmic reticulum (ER). Two key UPR regulators bZIP28 and bZIP60 have been shown to be essential for maintaining fertility under heat stress conditions in Arabidopsis, however, the function of transcriptional activator bZIP17, a paralog of bZIP28, in heat stress response at reproductive stage is not reported. Here we found that bzip17 mutant plants were sensitive to heat stress in terms of silique length and fertility comparing to that of wildtype (WT) Arabidopsis plants, and transcriptomic analysis showed that 1380 genes were specifically up-regulated and 493 genes were specifically down-regulated by heat stress in the flowers of WT plants comparing to that in bzip17 mutant plants. These bZIP17-dependent up-regulated genes were enriched in responses to abiotic stresses such as water deprivation and salt stress. Further chromatin immuno-precipitation coupled with high-throughput sequencing (ChIP-Seq) uncovered 1645 genes that were direct targets of bZIP17 in MYC-bZIP17 expressing seedlings subjected to heat stress. Among these 1645 genes, ERSE-II cis-element was enriched in the binding peaks of their promoters, and the up-regulation of 113 genes by heat stress in flowers was dependent on bZIP17. Our results revealed direct targets of bZIP17 in flowers during heat stress responses and demonstrated the important role of bZIP17 in maintaining fertility upon heat stress in plants.

Supplementary Information

The online version contains supplementary material available at 10.1007/s42994-021-00062-1.

Joint Determination of Reactor Antineutrino Spectra from ^{235}U and ^{239}Pu Fission by Daya Bay and PROSPECT

A joint determination of the reactor antineutrino spectra resulting from the fission of ^{235}U and ^{239}Pu has been carried out by the Daya Bay and PROSPECT Collaborations. This Letter reports the level of consistency of ^{235}U spectrum measurements from the two experiments and presents new results from a joint analysis of both data sets. The measurements are found to be consistent. The combined analysis reduces the degeneracy between the dominant ^{235}U and ^{239}Pu isotopes and improves the uncertainty of the ^{235}U spectral shape to about 3%. The ^{235}U and ^{239}Pu antineutrino energy spectra are unfolded from the jointly deconvolved reactor spectra using the Wiener-SVD unfolding method, providing a data-based reference for other reactor antineutrino experiments and other applications. This is the first measurement of the ^{235}U and ^{239}Pu spectra based on the combination of experiments at low- and highly enriched uranium reactors.

[Fibrinogen gamma-chain mutation, p.Ile171His, leads to hereditary hypofibrinogenemia]

Objective: To explore the clinical phenotype and genotype of a family with hereditary hypofibrinogenemia. Methods: Activated partial thrombin time (APTT), prothrombin time (PT),thrombin time (TT) and thrombelastogram (TEG) were tested in all family members. Fibrinogen activity and antigen were detected by Clauss method and immunoturbidimetric method respectively. All exons and flanking sequences of fibrinogen FGA,FGB,FGG genes were analyzed by PCR, and the products were subjected to Sanger sequencing. Results: The proband represented prolonged PT and TT, low Fg activity and antigen, elevated K value and decreased Angle value in TEG. Other family members reported similar changes including proband's father,daughter and son, and his elder brother and his niece. Exon 5 c.510_512 of FGG gene in the proband revealed a minor deletion mutation. Conclusion: The novel heterozygous missense mutation of exon 5 c.510_512del (Gln170_Ile171 del ins His) of FGG gene is the molecular mechanism that leads to hereditary hypofibrinogenemia in this family.

Roles of plant hormones in thermomorphogenesis

Global warming has great impacts on plant growth and development, as well as ecological distribution. Plants constantly perceive environmental temperatures and adjust their growth and development programs accordingly to cope with the environment under non-lethal warm temperature conditions. Plant hormones are endogenous bioactive chemicals that play central roles in plant growth, developmental, and responses to biotic and abiotic stresses. In this review, we summarize the important roles of plant hormones, including auxin, brassinosteroids (BRs), Gibberellins (GAs), ethylene (ET), and jasmonates (JAs), in regulating plant growth under warm temperature conditions. This provides a picture on how plants sense and transduce the warm temperature signals to regulate downstream gene expression for controlling plant growth under warm temperature conditions via hormone biosynthesis and signaling pathways.

Timing to grow: roles of clock in thermomorphogenesis

Plants coordinate their growth and developmental programs with changes in temperature. This process is termed thermomorphogenesis. The underlying molecular mechanisms have begun to emerge in these nonstressful responses to adjustments in prevailing temperature. The circadian clock is an internal timekeeper that ensures growth, development, and fitness across a wide range of environmental conditions and it responds to thermal changes. Here, we highlight how the circadian clock gates thermoresponsive hypocotyl growth in plants, with an emphasis on different action mode of evening complex (EC) in thermomorphogenesis. We also discuss the biochemical and molecular mechanisms of EC in transducing temperature signals to the key integrator PIF4. This provides future perspectives on unanswered questions on EC-associated thermomorphogenesis.

[Analysis on the status of occupational health of medical radiation workers in China in 2019]

Objective: To grasp the occupational health monitoring of radiation workers in medical institutions across the country, and to discover weak links in the prevention and treatment of occupational radiation diseases. Methods: In 2020 January, according to the monitoring data of the "National Radiation Health Information Platform" (Occupational Radiation Disease and Occupational Health Monitoring Subsystem and Occupational Radiation Disease Reporting Subsystem) , the national occupational health monitoring data from January 1 to December 31, 2019, including the number of radiation workers in medical institutions, occupational health examinations, personal dose monitoring and occupational radiation disease diagnosis, were descriptive analyzed. Results: There were a total of 394436 radiation workers in medical institutions across the country. The number of radiation workers in various provinces was quite different, with a median of 10206, which was positively correlated with the number of permanent residents in each province (r=0.947) . There were 376 personal dose monitoring institutions nationwide, and the personal dose monitoring rate of radiation workers in medical institutions was 96.61% (381045/394436) . There were 419 occupational health inspection institutions for radiation workers across the country, and 269 (64.20%) used software to print physical examination forms. A total of 334455 radiation workers in medical institutions had been subjected to occupational health examinations. The rate of occupational health examinations for radiation workers in medical institutions was 84.79% (334455/394436) . The abnormal rate of chromosomal aberrations in peripheral blood lymphocytes of radiation workers in medical institutions was 0.33% (776/233571) , the detection rate of posterior posterior subcapsular turbidity was 0.63% (2093/334455) , and the abnormality rate of thyroid color ultrasound was 28.49% (14946/52464) . In 2019, a total of 16 cases of occupational radiation diseases were reported. Conclusion: The personal dose monitoring rate and occupational health examination rate of medical radiation workers nationwide are relatively high, but the quality of lymphocyte chromosome aberration analysis, eye lens examination and thyroid color photograph examination needs to be further improved.

[Clinical characteristics and prognosis of MLL-AF6 positive patients with acute myeloid leukemia]

OBJECTIVE

To investigate the clinical features and prognosis of acute myeloid leukemia (AML) patients with the mixed lineage leukemia (MLL) gene rearrangements AF6 (MLL-AF6) positive.

METHODS

In the study, 11 patients who were newly diagnosed with MLL-AF6 positive AML were analyzed retrospectively, related literature was reviewed to clarify the clinical features and prognosis of MLL-AF6 positive patients.

RESULTS

Among the 11 patients, there were 6 males and 5 females, with a median age of 36 years. Six patients were diagnosed with AML M5 and five with M4 according to FAB classification (French-American-British classification systems). Gingival swelling and pain occurred in 6 cases and fever occurred in 5 cases. At first diagnosis, the median white blood cells were 55.5×109/L. Immunotype showed the expression of myeloid/monocyte and early stem cell series antigens. The expression level of MLL-AF6 fusion gene (real-time quantitative PCR) was 14.2%-214.5%, and 6/11 cases (54.5%) were associated with high EVI1 gene expression. Mutations of KRAS, TET2, ASXL1, TP53, DNMT3A, and FLT3-ITD were detected by next generation sequencing (NGS) in 4 patients. Chromosome G banding examination showed that 2 cases were t(6;11)(q27, q23) with complex karyotype abnormality, 4 cases with +8 abnormality and 2 cases with normal karyotype. Hematological complete remission (CR) was achieved in 8/11 patients (72.7%) after conventional induction chemotherapy, and primary drug resistance was observed in 3 patients. Two of the eight patients with CR were negative for minimal residual disease (MRD), with a median CR duration of 4.5 months. Two patients with positive MRD and three patients with refractory recurrence underwent allogeneic hematopoietic stem cell transplantation (allo-HSCT), but all died due to leukemia progression. At the end of follow-up on December 1, 2019, 2 patients were alive and 9 died, with median survival time of 9 months.

CONCLUSION

The AML patients with MLL-AF6 positive were mostly young, the majority of FAB types were M4 and M5, and most of the patients often had fever as the first symptom, with increased white blood cells, accompanied by organ infiltration, and high EVI1 gene expression. The hematological remission rate of routine chemotherapy is not low, but it is difficult to achieve molecular remission, most of which have early recurrence. Early allo-HSCT in a molecular negative state may prolong the CR duration.

Gene delivery strategies for therapeutic proteins production in plants: Emerging opportunities and challenges

There are sharply rising demands for pharmaceutical proteins, however shortcomings associated with traditional protein production methods are obvious. Genetic engineering of plant cells has gained importance as a new strategy for protein production. But most current genetic manipulation techniques for plant components, such as gene gun bombardment and Agrobacterium mediated transformation are associated with irreversible tissue damage, species-range limitation, high risk of integrating foreign DNAs into the host genome, and complicated handling procedures. Thus, there is urgent expectation for innovative gene delivery strategies with higher efficiency, fewer side effect, and more practice convenience. Materials based nanovectors have established themselves as novel vehicles for gene delivery to plant cells due to their large specific surface areas, adjustable particle sizes, cationic surface potentials, and modifiability. In this review, multiple techniques employed for plant cell-based genetic engineering and the applications of nanovectors are reviewed. Moreover, different strategies associated with the fusion of nanotechnology and physical techniques are outlined, which immensely augment delivery efficiency and protein yields. Finally, approaches that may overcome the associated challenges of these strategies to optimize plant bioreactors for protein production are discussed.

Effect of chromium methionine supplementation on lactation performance, hepatic respiratory rate and anti-oxidative capacity in early-lactating dairy cows

Chromium may regulate dairy cow metabolism; a chelated formation of chromium methionine (Cr-Met) is available to the feed industry. The objective of this study was to investigate the effect of Cr-Met supplementation on lactation performance, hepatic respiratory rate and anti-oxidative capacity in early-lactating Holstein dairy cows. 64 multiparous cows were assigned to 16 blocks based on parity and milk yield and then the four cows in a block were randomly allocated to four treatment groups with 0, 4, 8 or 16 g/d of Cr-Met per cow supplemented to a basal diet. Cows were moved from an open dry lot to a naturally ventilated tie stall barn 2 weeks before treatment to adapt to this facility, fed and milked at 0630, 1400, and 1930 h every day. The experiment lasted for 12 weeks. Milk yield and composition were recorded weekly. Dry matter intake was measured every 2 weeks for a total of six times throughout the trial. The plasma variables were measured in weeks 4, 8 and 12 of the experiment. Supplementation of Cr-Met did not affect DM intake of cows. As the supplementation of Cr-Met increased, yields of milk, fat, energy corrected milk (P < 0.01) and lactose (P = 0.01) increased in a linear manner. In terms of plasma variables, insulin concentration decreased in a linear manner with Cr-Met supplementation. As for variables relating to hepatic respiration rate, concentrations of pyruvate and NAD in the plasma were increased in quadratic manners, and lactic dehydrogenase activity was linearly increased as Cr-Met feeding levels increased. Moreover, plasma glutathione peroxidase and superoxide dismutase activity were increased in a linear manner. In conclusion, our study suggested that Cr-Met supplementation improved lactation performance of early-lactating dairy cows through enhancing antioxidant capacity and hepatic cellular respiration.

[Association of cadmium internal exposure with chronic kidney disease in Chinese adults]

Objective: To analyze the association of the cadmium internal exposure with chronic kidney disease (CKD) in Chinese adults aged 18 and older. Methods: A total of 9 821 adults aged 18-79 from the China National Human Biomonitoring (CNHBM) from 2017 to 2018 were included. Blood and urine cadmium exposure levels were measured by inductively coupled plasma mass spectrometry (ICP-MS), and urine cadmium levels were adjusted with urine creatinine; CKD were defined by estimated glomerular filtration (eGFR) using the chronic kidney disease epidemiology collaboration (CKD-EPI). Weights were considered due to complex sampling process for in statistical analysis. Logistic regression is used to analyze the association of blood cadmium, urine cadmium, and urine cadmium adjusted with creatinine exposure levels with CKD, and restricted cube spline (RCS) was used to assess the exposure-response curve of blood cadmium, urine cadmium and urine cadmium adjusted with creatinine with CKD. Results: The weighted age was 44.75 and males accounted for 61.1%. The prevalence rate of CKD was 12.7%. The geometric mean values of blood cadmium, urine cadmium, and urine cadmium adjusted with creatinine were 0.96 μg/L, 0.61 μg/L, and 0.58 μg/g. After adjusting for confounding factors, the weighted logistic regression showed that the lowest quintile (Q1) was compared with the odds ratio (OR) of the highest quintile (Q5) of blood cadmium, urine cadmium, and urine cadmium adjusted with creatinine and the 95% confidence interval (CI) was 1.80 (1.02-3.20), 1.77 (0.94-3.31) and 1.94 (1.11-3.37) respectively. In the restricted cubic spline regression model, non-linear association of blood cadmium, urine cadmium, and urine cadmium adjusted with creatinine with CKD were observed after adjusting for related confounding factors (P<0.001, 0.018, 0.031 respectively). The risk of CKD increased with the increment of cadmium exposure without risk threshold, and the exposure response curve was steeper at low cadmium exposure. Conclusions: Among Chinese adults aged 18 and older, cadmium exposure is positively associated with the risk of chronic kidney disease.

The E3 ligase XBAT35 mediates thermoresponsive hypocotyl growth by targeting ELF3 for degradation in Arabidopsis

Plants are capable of coordination of their growth and development with ambient temperatures. EARLY FLOWERING3 (ELF3), an essential component of the plant circadian clock, is also involved in ambient temperature sensing, as well as in inhibiting the expression and protein activity of the thermoresponsive regulator phytochrome interacting factor 4 (PIF4). The ELF3 activity is subjected to attenuation in response to warm temperature; however, how the protein level of ELF3 is regulated at warm temperature remains less understood. Here, we report that the E3 ligase XB3 ORTHOLOG 5 IN ARABIDOPSIS THALIANA, XBAT35, mediates ELF3 degradation. XBAT35 interacts with ELF3 and ubiquitinates ELF3. Loss-of-function mutation of XBAT35 increases the protein level of ELF3 and confers a short-hypocotyl phenotype under warm temperature conditions. Thus, our findings establish that XBAT35 mediates ELF3 degradation to lift the inhibition of ELF3 on PIF4 for promoting thermoresponsive hypocotyl growth in plants.

[Effectiveness of abdominal minimal incision sacrocolpopexy for advanced pelvic organ prolapse]

Objective: To evaluate the indications, surgical skills and clinic outcomes of abdominal minimal incision sacrocolpopexy (AMISC) for treatment of advanced pelvic organ prolapse (POP). Methods: The retrospective study analyzed 30 women with advanced POP who underwent AMISC between June 2016 and October 2019, including 9 cases of recurrent prolapse and 10 cases of vault prolapse. AMISC was especially applicable to: (1) patients with several medical complications who was unable to tolerate general anesthesia or laparoscopic surgery, but able to tolerate combined spinal-epidural anesthesia and open surgery; (2) other abdominal procedures were indicated to perform with AMISC simultaneously, such as myomectomy, subtotal hysterectomy etc, the specimens were easy to get out of the abdominal cavity and morcellation was avoided; (3) surgeons preferring open surgery to laparoscopic surgery or skilled in open surgery; (4) patients with prior pelvic operations, presenting severe abdominal and pelvic adhesions. Objective outcomes were assessed by pelvic organ prolapse quantification (POP-Q) system. Subjective outcome were assessed by pelvic floor distress inventory-short form 20 (PFDI-20), pelvic floor impact questionnaire-short form (PFIQ-7) and patient global impression of improvement (PGI-I). Results: All patients with 1-3 medical complications were successfully performed with AMISC without stopping procedure, enlarging the incision or changing to other procedure, the operation duration was (110±19) minutes. The mean time of follow-up was (33.5±12.4) months (range: 8-49 months). The postoperative points of Aa, Ba, C, Ap, Bp reduced significantly and point C improved from (2.33±2.50) cm to (-7.54±1.18) cm after AMISC (P<0.01). The objective cure rates were both 100% (30/30) in apex and posterior compartment, while 97% (29/30) in anterior compartment. Postoperative scores of PFDI-20 and PFIQ-7 were all significant decreased (all P<0.01). About PGI-I, 29 patients chose "significant improvement", subjective satisfaction was 97% (29/30). Anterior sacral plexus hemorrhage occurred in 2 cases (7%, 2/30). There was no intestinal obstruction or injury of bladder, bowel and ureter intra- and postoperation. Two cases (7%, 2/30) had mesh exposure. Conclusion: AMISC is a safety, convenient, minimal traumatic and durable procedure for apical prolapse with short learning curve in the most of cases.

Two B-box domain proteins, BBX28 and BBX29, regulate flowering time at low ambient temperature in Arabidopsis

This paper demonstrates that BBX28 and BBX29 proteins in Arabidopsis promote flowering in association with the CO-FT regulatory module at low ambient temperature under LD conditions. Flowering plants integrate internal developmental signals with external environmental stimuli for precise flowering time control. The expression of BBX29 is up-regulated by low temperature treatment, but the biological function of BBX29 in low temperature response is unknown. In the current study, we examined the biological role of BBX29 and its close-related protein BBX28 in flowering time control under long-day conditions. Although neither BBX28 single mutant nor BBX29 single mutant has a flowering-associated phenotype, the bbx28 bbx29 double mutant plants have an obvious delayed flowering phenotype grown at low ambient temperature (16°C) compared to the wild-type (WT) plants. The expression of FT and TSF was lower in bbx28 bbx29 double mutant plants than in wild-type plants at 16°C. Both BBX28 and BBX29 interact with CONSTANS (CO), an important flowering integrator that directly binds to the FLOWERING LOCUS T (FT) promoter. In the effector-reporter assays, transcriptional activation activity of CO on the FT promoter was reduced in bbx28 bbx29 double mutant plants compared to that in WT plants. Taken together, our results reveal that BBX28 and BBX29 are promoters of flowering in Arabidopsis, especially at low ambient temperature.

Histone H3K4 methyltransferases SDG25 and ATX1 maintain heat-stress gene expression during recovery in Arabidopsis

Plants have short-term stress memory that enables them to maintain the expression state of a substantial subset of heat-inducible genes during stress recovery after heat stress. Little is known about the molecular mechanisms controlling stress-responsive gene expression at the recovery stage in plants, however. In this article, we demonstrate that histone H3K4 methyltransferases SDG25 and ATX1 are required for heat-stress tolerance in Arabidopsis. SDG25 and ATX1 are not only important for stress-responsive gene expression during heat stress, but also for maintaining stress-responsive gene expression during stress recovery. A combination of whole-genome bisulfite sequencing, RNA-sequencing and ChIP-qPCR demonstrated that mutations of SDG25 and ATX1 decrease histone H3K4me3 levels, increase DNA cytosine methylation and inhibit the expression of a subset of heat stress-responsive genes during stress recovery in Arabidopsis. ChIP-qPCR results confirm that ATX1 binds to chromatins associated with these target genes. Our results reveal that histone H3K4me3 affects DNA methylation at regions in the loci associated with heat stress-responsive gene expression during stress recovery, providing insights into heat-stress transcriptional memory in plants.

Chromatin remodeling factors regulate environmental stress responses in plants

Environmental stress from climate change and agricultural activity threatens global plant biodiversity as well as crop yield and quality. As sessile organisms, plants must maintain the integrity of their genomes and adjust gene expression to adapt to various environmental changes. In eukaryotes, nucleosomes are the basic unit of chromatin around which genomic DNA is packaged by condensation. To enable dynamic access to packaged DNA, eukaryotes have evolved Snf2 (sucrose nonfermenting 2) family proteins as chromatin remodeling factors (CHRs) that modulate the position of nucleosomes on chromatin. During plant stress responses, CHRs are recruited to specific genomic loci, where they regulate the distribution or composition of nucleosomes, which in turn alters the accessibility of these loci to general transcription or DNA damage repair machinery. Moreover, CHRs interplay with other epigenetic mechanisms, including DNA methylation, histone modifications, and deposition of histone variants. CHRs are also involved in RNA processing at the post-transcriptional level. In this review, we discuss major advances in our understanding of the mechanisms by which CHRs function during plants' response to environmental stress.

Ectopic overexpression of a membrane-tethered transcription factor gene NAC60 from oilseed rape positively modulates programmed cell death and age-triggered leaf senescence

Senescence is an integrative final stage of plant development that is governed by internal and external cues. The NAM, ATAF1/2, CUC2 (NAC) transcription factor (TF) family is specific to plants and membrane-tethered NAC TFs (MTTFs) constitute a unique and sophisticated mechanism in stress responses and development. However, the function of MTTFs in oilseed rape (Brassica napus L.) remains unknown. Here, we report that BnaNAC60 is an MTTF associated with the endoplasmic reticulum (ER) membrane. Expression of BnaNAC60 was induced during the progression of leaf senescence. Translocation of BnaNAC60 into nuclei was induced by ER stress and oxidative stress treatments. It binds to the NTLBS motif, rather than the canonical NAC recognition site. Overexpression of BnaNAC60 devoid of the transmembrane domain, but not the full-length BnaNAC60, induces significant reactive oxygen species (ROS) accumulation and hypersensitive response-like cell death in both tobacco (Nicotiana benthamiana) and oilseed rape protoplasts. Moreover, ectopic overexpression of BnaNAC60 devoid of the transmembrane domain, but not the full-length BnaNAC60, in Arabidopsis also induces precocious leaf senescence. Furthermore, screening and expression profiling identified an array of functional genes that are significantly induced by BnaNAC60 expression. Further it was found that BnaNAC60 can activate the promoter activities of BnaNYC1, BnaRbohD, BnaBFN1, BnaZAT12, and multiple BnaVPEs in a dual-luciferase reporter assay. Electrophoretic mobility shift assay and chromatin immunoprecipitation coupled to quantitative PCR assays revealed that BnaNAC60 directly binds to the promoter regions of these downstream target genes. To summarize, our data show that BnaNAC60 is an MTTF that modulates cell death, ROS accumulation, and leaf senescence.

SP1-induced long non-coding RNA SNHG6 facilitates the carcinogenesis of chondrosarcoma through inhibiting KLF6 by recruiting EZH2

Small nucleolar RNA host gene 6 (SNHG6) is a newly discovered long non-coding RNA (lncRNA), while the regulatory mechanism of SNHG6 in chondrosarcoma is largely unknown. Here we found that SNHG6 expression was upregulated and showed positive correlation with the progression of chondrosarcoma. Functional assays demonstrated that SNHG6 was required for the proliferation, migration, and invasion of chondrosarcoma cells. Mechanistic study revealed that SNHG6 could recruit EZH2 and maintain high level of H3K27me3 to repress the transcription of tumor-suppressor genes, including KLF6. KLF6 was found to bind to the promoter region of SP1 and restrained its transcription, while SP1 could be recruited to the promoter region of SNHG6 and promoted its transcription to form a positive loop. In summary, this study reveals that SP1-induced SNHG6 forms a positive loop to facilitate the carcinogenesis of chondrosarcoma through the suppression of KLF6 by recruiting EZH2, which manifests the oncogenic function of SNHG6 in chondrosarcoma.

Protein Quality Control in Plant Organelles: Current Progress and Future Perspectives

The endoplasmic reticulum, chloroplasts, and mitochondria are major plant organelles for protein synthesis, photosynthesis, metabolism, and energy production. Protein homeostasis in these organelles, maintained by a balance between protein synthesis and degradation, is essential for cell functions during plant growth, development, and stress resistance. Nucleus-encoded chloroplast- and mitochondrion-targeted proteins and ER-resident proteins are imported from the cytosol and undergo modification and maturation within their respective organelles. Protein folding is an error-prone process that is influenced by both developmental signals and environmental cues; a number of mechanisms have evolved to ensure efficient import and proper folding and maturation of proteins in plant organelles. Misfolded or damaged proteins with nonnative conformations are subject to degradation via complementary or competing pathways: intraorganelle proteases, the organelle-associated ubiquitin-proteasome system, and the selective autophagy of partial or entire organelles. When proteins in nonnative conformations accumulate, the organelle-specific unfolded protein response operates to restore protein homeostasis by reducing protein folding demand, increasing protein folding capacity, and enhancing components involved in proteasome-associated protein degradation and autophagy. This review summarizes recent progress on the understanding of protein quality control in the ER, chloroplasts, and mitochondria in plants, with a focus on common mechanisms shared by these organelles during protein homeostasis.

Phosphoproteomic Analysis of Thermomorphogenic Responses in Arabidopsis

Plants rapidly adapt to elevated ambient temperature by adjusting their growth and developmental programs. To date, a number of experiments have been carried out to understand how plants sense and respond to warm temperatures. However, how warm temperature signals are relayed from thermosensors to transcriptional regulators is largely unknown. To identify new early regulators of plant thermo-responsiveness, we performed phosphoproteomic analysis using TMT (Tandem Mass Tags) labeling and phosphopeptide enrichment with Arabidopsis etiolated seedlings treated with or without 3h of warm temperatures (29°C). In total, we identified 13,160 phosphopeptides in 5,125 proteins with 10,700 quantifiable phosphorylation sites. Among them, 200 sites (180 proteins) were upregulated, while 120 sites (87 proteins) were downregulated by elevated temperature. GO (Gene Ontology) analysis indicated that phosphorelay-related molecular function was enriched among the differentially phosphorylated proteins. We selected ATL6 (ARABIDOPSIS TOXICOS EN LEVADURA 6) from them and expressed its native and phosphorylation-site mutated (S343A S357A) forms in Arabidopsis and found that the mutated form of ATL6 was less stable than that of the native form both in vivo and in cell-free degradation assays. Taken together, our data revealed extensive protein phosphorylation during thermo-responsiveness, providing new candidate proteins/genes for studying plant thermomorphogenesis in the future.