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According to the \"state transitions'' theory, the light-harvesting complex II (LHCII) phosphorylation in plant chloroplasts is essential to adjust the relative absorption cross section of photosystem II (PSII) and PSI upon changes in light quality. The role of LHCII phosphorylation upon changes in light intensity is less thoroughly investigated, particularly when changes in light intensity are too fast to allow the phosphorylation/dephosphorylation processes to occur. Here, we demonstrate that the Arabidopsis (Arabidopsis thaliana) stn7 (for state transition7) mutant, devoid of the STN7 kinase and LHCII phosphorylation, shows a growth penalty only under fluctuating white light due to a low amount of PSI. Under constant growth light conditions, stn7 acquires chloroplast redox homeostasis by increasing the relative amount of PSI centers. Thus, in plant chloroplasts, the steady-state LHCII phosphorylation plays a major role in preserving PSI upon rapid fluctuations in white light intensity. Such protection of PSI results from LHCII phosphorylation-dependent equal distribution of excitation energy to both PSII and PSI from the shared LHCII antenna and occurs in cooperation with nonphotochemical quenching and the proton gradient regulation5-dependent control of electron flow, which are likewise strictly regulated by white light intensity. LHCII phosphorylation is concluded to function both as a stabilizer (in time scales of seconds to minutes) and a dynamic regulator (in time scales from tens of minutes to hours and days) of redox homeostasis in chloroplasts, subject to modifications by both environmental and metabolic cues. Exceeding the capacity of LHCII phosphorylation/dephosphorylation to balance the distribution of excitation energy between PSII and PSI results in readjustment of photosystem stoichiometry.

In nature, plants are challenged by constantly changing light conditions. To reveal the molecular mechanisms behind acclimation to sometimes drastic and frequent changes in light intensity, we grew Arabidopsis thaliana under fluctuating light conditions, in which the low light periods were repeatedly interrupted with high light peaks. Such conditions had only marginal effect on photosystem II but induced damage to photosystem I (PSI), the damage being most severe during the early developmental stages. We showed that PROTON GRADIENT REGULATIONS (PGR5)—dependent regulation of electron transfer and proton motive force is crucial for protection of PSI against photodamage, which occurred particularly during the high light phases of fluctuating light cycles. Contrary to PGR5, the NAD(P)H dehydrogenase complex, which mediates cyclic electron flow around PSI, did not contribute to acclimation of the photosynthetic apparatus, particularly PSI, to rapidly changing light intensities. Likewise, the Arabidopsis pgr5 mutant exhibited a significantly higher mortality rate compared with the wild type under outdoor field conditions. This shows not only that regulation of PSI under natural growth conditions is crucial but also the importance of PGR5 in PSI protection.

Safe and efficient conversion of solar energy to metabolic energy by plants is based on tightly inter-regulated transfer of excitation energy, electrons and protons in the photosynthetic machinery according to the availability of light energy, as well as the needs and restrictions of metabolism itself. Plants have mechanisms to enhance the capture of energy when light is limited for growth and development. Also, when energy is in excess, the photosynthetic machinery slows down the electron transfer reactions in order to prevent the production of reactive oxygen species and the consequent damage of the photosynthetic machinery. In this opinion paper, we present a partially hypothetical scheme describing how the photosynthetic machinery controls the flow of energy and electrons in order to enable the maintenance of photosynthetic activity in nature under continual fluctuations in white light intensity. We discuss the roles of light-harvesting II protein phosphorylation, thermal dissipation of excess energy and the control of electron transfer by cytochrome b6f, and the role of dynamically regulated turnover of photosystem II in the maintenance of the photosynthetic machinery. We present a new hypothesis suggesting that most of the regulation in the thylakoid membrane occurs in order to prevent oxidative damage of photosystem I.

Several proteins of photosystem II (PSII) and its light-harvesting antenna (LHCII) are reversibly phosphorylated according to light quantity and quality. Nevertheless, the interdependence of protein phosphorylation, nonphotochemical quenching, and efficiency of electron transfer in the thylakoid membrane has remained elusive. These questions were addressed by investigating in parallel the wild type and the stn7, stn8, and stn7 stn8 kinase mutants of Arabidopsis (Arabidopsis thaliana), using the stn7 npq4, npq4, npq1, and pgr5 mutants as controls. Phosphorylation of PSII-LHCII proteins is strongly and dynamically regulated according to white light intensity. Yet, the changes in phosphorylation do not notably modify the relative excitation energy distribution between PSII and PSI, as typically occurs when phosphorylation is induced by \"state 2\" light that selectively excites PSII and induces the phosphorylation of both the PSII core and LHCII proteins. On the contrary, under low-light conditions, when excitation energy transfer from LHCII to reaction centers is efficient, the STN7-dependent LHCII protein phosphorylation guarantees a balanced distribution of excitation energy to both photosystems. The importance of this regulation diminishes at high light upon induction of thermal dissipation of excitation energy. Lack of the STN7 kinase, and thus the capacity for equal distribution of excitation energy to PSII and PSI, causes relative overexcitation of PSII under low light but not under high light, leading to disturbed maintenance of fluent electron flow under fluctuating light intensities. The physiological relevance of the STN7-dependent regulation is evidenced by severely stunted phenotypes of the stn7 and stn7 stn8 mutants under strongly fluctuating light conditions.

The Arabidopsis thaliana genes PROTEIN INHIBITOR OF ACTIVATED STAT LIKE1 (PIAL1) and PIAL2 encode proteins with domains, which occur in many ligases of the small ubiquitin-related modifier (SUMO) conjugation pathway. We show that PIAL1 and PIAL2 function as SUMO ligases capable of SUMO chain formation and require the SUMO-modified SUMO-conjugating enzyme SCE1 for optimal activity. Mutant analysis indicates a role for PIAL1 and 2 in salt stress and osmotic stress responses, whereas under standard conditions, the mutants show close to normal growth. Mutations in PIAL1 and 2 also lead to altered sulfur metabolism. We propose that, together with SUMO chain binding ubiquitin ligases, these enzymes establish a pathway for proteolytic removal of sumoylation substrates.

Chromobox (CBX) proteins play a crucial role in regulating epigenetic processes. They are extensively involved in various biological processes, including embryonic development, stem cell maintenance, cell proliferation and apoptosis control. The disruption and malfunction of CBXs in cancer typically results in the interference or abnormal activation of developmental pathways, which facilitate the onset, growth, and advancement of cancer. This review initially introduces the physiological properties and functions of the CBXs. Subsequently, it examines the involvement of CBXs in different cancer types. Cancer hallmarks driven by CBXs are mediated through multiple mechanisms, including changes in gene expression patterns, epigenetic dysregulation of chromatin control, disruption of intracellular signaling and alterations in cell metabolism. The study also highlights novel potential anticancer therapeutics targeting CBXs in cancer. In this review we provide novel perspectives and a solid foundation for future investigations on CBXs as promising therapeutic targets for cancer treatment.

Left-sided acute diverticulitis in WSES Stage 0-IIb preferentially undergoes conservative management. However, there is limited understanding of the risk factors for failure of this approach. The aim of this study was to investigate the factors associated with the decision to perform conservative treatment as well as the predictors of its failure. We included patients with a diagnosis of WSES diverticulitis CT-driven classification Stage 0-IIb treated in the Emergency Surgery Unit of the Agostino Gemelli University Hospital Foundation between 2014 and 2020. The endpoints were the comparison between the characteristics and clinical outcomes of acute diverticulitis patients undergoing conservative versus operative treatment. We also identified predictors of conservative treatment failure. A set of multivariable backward logistic analyses were conducted for this purpose. The study included 187 patients. The choice for operative versus conservative treatment was associated with clinical presentation, older age, higher WSES grade, and previous conservative treatment. There were 21% who failed conservative treatment. Of those, major morbidity and mortality rates were 17.9% and 7.1%, respectively. A previously failed conservative treatment as well as a greater WSES grade and a lower hemoglobin value were significantly associated with failure of conservative treatment. WSES classification and hemoglobin value at admission were the best predictors of failure of conservative treatment. Patients failing conservative treatment had non-negligible morbidity and mortality. These results promote the consideration of a combined approach including baseline patients’ characteristics, radiologic features, and laboratory biomarkers to predict conservative treatment failure and therefore optimize treatment of acute diverticulitis.

Background Efficient hemostatic techniques are essential in laparoscopic surgery for ideal intraoperative and postoperative results. A variety of advanced devices are available for the sealing of major vascular structures. The aim of this study is to assess effectiveness and safety of major vessel sealing with a radiofrequency device during laparoscopic colorectal resections for cancer based on the experience of a single hospital. Methods Early outcomes of a consecutive series of patients who received elective laparoscopic colorectal resections for cancer over a 10-year period (January 2008–September 2017) are analyzed. In all procedures, the Ligasure® electrothermal bipolar device was used for the closure of the major colonic vessels and the dissection of all the structures. No other products such clips, staplers, hemostatic products, or other devices were used. Results Seven-hundred fifty-nine procedures were performed in laparoscopy: 179 rectal resections, 247 sigmoidectomies and left hemicolectomies, 240 right hemicolectomies, 33 resections of the splenic flexure, 35 transverse colonic resections, and 25 other procedures. In 39 cases, the laparoscopic procedure was converted to open surgery, and in these cases, vessel sealing was also achieved with the radiofrequency device alone. Vessel dissection and sealing was realized in all cases without any intraoperative or postoperative bleeding. No reoperations for bleeding from major vessels were performed in any patients. One case of reoperation was recorded postoperatively, at 3 h after right hemicolectomy, due to a small bleeding from the fat of the transverse colon stump. Conclusions The use of Ligasure® radiofrequency device for sealing and dividing the major colonic vessels is safe, fast, and effective during laparoscopic colorectal resections.

With ongoing climate change, drought events are becoming more frequent and will affect biomass formation when occurring during pre-flowering stages. We explored growth over time under such a drought scenario, via non-invasive imaging and revealed the underlying key genetic factors in spring barley. By comparing with well-watered conditions investigated in an earlier study and including information on timing, QTL could be classified as constitutive, drought or recovery-adaptive. Drought-adaptive QTL were found in the vicinity of genes involved in dehydration tolerance such as dehydrins ( Dhn4, Dhn7, Dhn8 , and Dhn9 ) and aquaporins (e.g. HvPIP1;5, HvPIP2;7 , and HvTIP2;1 ). The influence of phenology on biomass formation increased under drought. Accordingly, the main QTL during recovery was the region of HvPPD-H1 . The most important constitutive QTL for late biomass was located in the vicinity of HvDIM , while the main locus for seedling biomass was the HvWAXY region. The disappearance of QTL marked the genetic architecture of tiller number. The most important constitutive QTL was located on 6HS in the region of 1-FEH . Stage and tolerance specific QTL might provide opportunities for genetic manipulation to stabilize biomass and tiller number under drought conditions and thereby also grain yield.