Thylakoid Protein Phosphorylation in Regulation of Photosynthesis

Once the seed has germinated, the plant is forced to face all the environmental changes in its habitat. In order to survive, plants have evolved a number of different acclimation systems. The primary reaction behind plant growth and development is photosynthesis. Photosynthesis captures solar energy and converts it into chemical form. Photosynthesis in turn functions under the control of environmental cues, but is also affected by the growth, development, and metabolic state of a plant. The availability of solar energy fluctuates continuously, requiring non-stop adjustment of photosynthetic efficiency in order to maintain the balance between photosynthesis and the requirements and restrictions of plant metabolism. Tight regulation is required, not only to provide sufficient energy supply but also to prevent the damage caused by excess energy. The very first reaction of photosynthesis is splitting of water into the form of oxygen, hydrogen, and electrons. This most fundamental reaction of life is run by photosystem II (PSII), and the energy required for the reaction is collected by the light harvesting complex II (LHCII). Several proteins of the PSII-LHCII complex are reversibly phosphorylated according to the energy balance between photosynthesis and metabolism. Thylakoid protein phosphorylation has been under extensive investigation for over 30 years, yet the physiological role of phosphorylation remains elusive. Recently, the kinases behind the phosphorylation of PSII-LHCII proteins (STN7 and STN8) were identified and the knockout mutants of these kinases became available, providing powerful tools to elucidate the physiological role of PSII-LHCII phosphorylation. In my work I have used the stn7 and stn8 mutants in order to clarify the role of PSII-LHCII phosphorylation in regulation and protection of the photosynthetic machinery according to environmental cues. I show that STN7- dependent PSII-LHCII protein phosphorylation is required to balance the excitation energy distribution between PSII and PSI especially under low light intensities when the excitation energy transfer from LHC to PSII and PSI is efficient. This mechanism differs from traditional light quality-induced “state 1” – “state 2” transition and ensures fluent electron transfer from PSII to PSI under low light, yet having highest physiological relevance under fluctuating light intensity. STN8-dependent phosphorylation of PSII proteins, in turn, is required for fluent turn-over of photodamaged PSII complexes and has the highest importance upon prolonged exposure of the photosynthetic apparatus to excess light.Siirretty Doriast

Phosphorylation-induced lateral rearrangements of thylakoid protein complexes upon light acclimation

Understanding the mechanistic basis of balanced excitation energy distributionbetween photosystem II and photosystem I (PSII and PSI) requires detailed investigationof the thylakoid light-harvesting system composed of energetically connectedLHCII trimers. The exact mechanisms controlling the excitation energy distributionremain elusive, but reversible phosphorylation is known to be one important component.Here, we addressed the role of grana margins in regulation of excitationenergy distribution, as these thylakoid domains host all the complexes of photosyntheticlight reactions with dynamic response to environmental cues. First, the effectof detergents for the thylakoid membrane connectivity is explained. We show thata specific interaction between the separate LHCII trimers as well as between theLHCII trimers and the PSII and PSI–LHCI complexes is a prerequisite for energeticallyconnected and functional thylakoid membrane. Second, we demonstrate thatthe optimization of light reactions under changing light conditions takes place inenergetically connected LHCII lake and is attained by lateral rearrangements of thePSII–LHCII and PSI–LHCI–LHCII complexes depending especially on the phosphorylationstatus of the LHCII protein isoform LHCB2.</p

Major or minor placenta previa : Does it make a difference?

Introduction: Placenta previa is a severe pregnancy complication with considerable maternal and neonatal morbidity. Placenta previa can be defined as major or minor by location. Major placenta previa is associated with higher complication rates. Management of women with minor placenta previa has not been well defined. The primary goal of the study was to evaluate the accuracy of our existing screening protocol for placenta previa. Secondly, we wanted to compare pregnancy and delivery outcomes by the type of placenta previa. Methods: The study was conducted at the Helsinki University Hospital between June 2010 and September 2014. The study population consisted of all women with the antenatal ultrasound diagnosis of placenta previa during delivery. Data were retrospectively collected and analysed. Results: Altogether 176 women had placenta previa at delivery (major 129, minor 47). Placenta previa remained undiagnosed at second trimester screening ultrasound in 32 women (18.2%). Twenty (62.5%) of these cases had minor placenta previa and 12 (37.5%) had major placenta previa. Five (15.6%) of the undiagnosed cases developed life-threatening hemorrhage (>= 2500 ml) during the delivery and two had abnormally invasive placenta followed by hysterectomy. Women with major placenta previa had significantly more blood loss and delivered earlier than women with minor placenta previa. The groups were otherwise similar, including the rate of abnormally invasive placenta. Discussion: The existing protocol for placenta previa missed almost one fifth of cases. Both major and minor placenta previa are risk factors for abnormally invasive placenta and should be treated as severe conditions.Peer reviewe

Simultaneous Ozone and High Light Treatments Reveal an Important Role for the Chloroplast in Co-ordination of Defense Signaling

Plants live in a world of changing environments, where they are continuously challenged by alternating biotic and abiotic stresses. To transfer information from the environment to appropriate protective responses, plants use many different signaling molecules and pathways. Reactive oxygen species (ROS) are critical signaling molecules in the regulation of plant stress responses, both inside and between cells. In natural environments, plants can experience multiple stresses simultaneously. Laboratory studies on stress interaction and crosstalk at regulation of gene expression, imply that plant responses to multiple stresses are distinctly different from single treatments. We analyzed the expression of selected marker genes and reassessed publicly available datasets to find signaling pathways regulated by ozone, which produces apoplastic ROS, and high light treatment, which produces chloroplastic ROS. Genes related to cell death regulation were differentially regulated by ozone versus high light. In a combined ozone + high light treatment, the light treatment enhanced ozone-induced cell death in leaves. The distinct responses from ozone versus high light treatments show that plants can activate stress signaling pathways in a highly precise manner.Peer reviewe

Is there an association between postpartum hemorrhage, interventional radiology procedures, and psychological sequelae?

Background: Postpartum hemorrhage (PPH) may cause post-traumatic psychological sequelae. Interventional radiology procedures (IRP) have been established in the management of PPH when conventional management fails. IRP is also used prophylactically in women who are at high risk for PPH in pregnancies with abnormally invasive placentation. We sought to determine if there is an association between PPH, IRP, and psychological sequelae. Objectives: Seventy-three women who underwent IRP due to PPH or were at high risk for PPH. Method: A structured questionnaire was sent to all women. Results: Overall 49 women returned the questionnaire. Two-thirds of the women developed psychological sequelae and one-third reported a lack of professional support. Nine women had symptoms of post-traumatic stress disorder. Psychological sequelae were not associated with a volume of bleeding, whether or not hysterectomy was performed, or whether the IRP was performed as an emergency procedure or prophylactically. However, women who had elective IRP and no hysterectomy performed had significantly less fear of death compared to the rest of the study population. Conclusions: We observed a high rate of psychological sequelae associated with IRP. Lack of proper professional support may have contributed to the development of post-traumatic psychological sequelae suggesting a need for debriefing in such women.Peer reviewe

Challenges and Solutions for Non-Timber Forest Product Businesses in FINLAND : An Application of the SODA Analysis

This study aims to present a holistic image of the strategic development needs and potential solutions within the Finnish non-timber forest product (NTFP) business sector and demonstrate a new hybrid methodology for collaborative strategy formulation. The perceived challenges and solutions were collected with the 635 group-working method in a nationwide series of NTFP actor workshops. The analysis applied the Strategic Option Development and Analysis (SODA) approach and the formal network analysis. Business actors emphasised two complex and interrelated aims of development at the core of the business activity: (1) to improve the profitability of the NTFP business and (2) to facilitate the growth of the sector. The present bottleneck is perceived in the raw material acquisition and productising, and many wider development themes, such as business logic and sustainability, received little attention

Plants acclimate to Photosystem I photoinhibition by readjusting the photosynthetic machinery

Photosynthetic light reactions require strict regulation under dynamic environmental conditions. Still, depending on environmental constraints, photoinhibition of Photosystem (PSII) or PSI occurs frequently. Repair of photodamaged PSI, in sharp contrast to that of PSII, is extremely slow and leads to a functional imbalance between the photosystems. Slow PSI recovery prompted us to take advantage of the PSI-specific photoinhibition treatment and investigate whether the imbalance between functional PSII and PSI leads to acclimation of photosynthesis to PSI-limited conditions, either by short-term or long-term acclimation mechanisms as tested immediately after the photoinhibition treatment or after 24 h recovery in growth conditions, respectively. Short-term acclimation mechanisms were induced directly upon inhibition, including thylakoid protein phosphorylation that redirects excitation energy to PSI as well as changes in the feedback regulation of photosynthesis, which relaxed photosynthetic control and excitation energy quenching. Longer-term acclimation comprised reprogramming of the stromal redox system and an increase in ATP synthase and Cytochrome b6f abundance. Acclimation to PSI-limited conditions restored the CO2 assimilation capacity of plants without major PSI repair. Response to PSI inhibition demonstrates that plants efficiently acclimate to changes occurring in the photosynthetic apparatus, which is likely a crucial component in plant acclimation to adverse environmental conditions.</p

Simultaneous Ozone and High Light Treatments Reveal an Important Role for the Chloroplast in Co-ordination of Defense Signaling

Plants live in a world of changing environments, where they are continuously challenged by alternating biotic and abiotic stresses. To transfer information from the environment to appropriate protective responses, plants use many different signaling molecules and pathways. Reactive oxygen species (ROS) are critical signaling molecules in the regulation of plant stress responses, both inside and between cells. In natural environments, plants can experience multiple stresses simultaneously. Laboratory studies on stress interaction and crosstalk at regulation of gene expression, imply that plant responses to multiple stresses are distinctly different from single treatments. We analyzed the expression of selected marker genes and reassessed publicly available datasets to find signaling pathways regulated by ozone, which produces apoplastic ROS, and high light treatment, which produces chloroplastic ROS. Genes related to cell death regulation were differentially regulated by ozone versus high light. In a combined ozone + high light treatment, the light treatment enhanced ozone-induced cell death in leaves. The distinct responses from ozone versus high light treatments show that plants can activate stress signaling pathways in a highly precise manner

Increased myeloid cell hypoxia-inducible factor-1 delays obliterative airway disease in the mouse

BACKGROUND: Obliterative bronchiolitis after lung transplantation is characterized by chronic airway inflammation leading to the obliteration of small airways. Hypoxia-inducible factor-1 (HIF-1) is a master regulator of cellular responses to hypoxia and inflammation. The Von Hippel-Lindau protein (pVHL) drives the degradation of oxygen-sensitive subunit HIF-1 alpha that controls the activity of HIF-1. We investigated the effect of myeloid cell targeted gene deletion of HIF-1 alpha or its negative regulator pVHL on the development of obliterative airway disease (OAD) in the recipients of tracheal allografts, a mouse model for obliterative bronchiolitis after lung transplantation. METHODS: Tracheal allografts were heterotopically transplanted from BALB/c donor mice to fully major histocompatibility complex mismatched recipient mice with HIF-1 alpha or VHL gene deletion in myeloid cells. The recipients were left non-immunosuppressed or received tacrolimus daily. Histologic, immunohistochemical, and real-time reverse transcription polymerase chain reaction analyses were performed at 3, 10, and 30 days. RESULTS: In the absence of immunosuppression, myeloid cell-specific VHL deficiency of the recipient mice improved epithelial recovery, decreased inflammatory cell infiltration and expression of pro-inflammatory cytokines, increased regulatory forkhead box P3 messenger RNA expression, and reduced OAD development in tracheal allografts. In the presence of tacrolimus immunosuppression, loss of HIF-1 alpha activity in myeloid cells of the recipient by HIF-1 alpha gene deletion accelerated OAD development in mouse tracheal allografts. CONCLUSIONS: Activity of the HIF-pathway affects the development of allograft rejection, and our results suggest that myeloid cell-specific VHL-deficiency that potentially increases HIF-activity decreases allograft inflammation and the subsequent development of OAD in mouse tracheal allografts. (C) 2016 International Society for Heart and Lung Transplantation. All rights reserved.Peer reviewe

Estrogen biosynthesis in breast adipose tissue during menstrual cycle in women with and without breast cancer

Circulating estrogens fluctuate during the menstrual cycle but it is not known whether this fluctuation is related to local hormone levels in adipose tissue. We analyzed estrogen concentrations and gene expression of estrogen-regulating enzymes in breast subcutaneous adipose tissue in premenopausal women with (n = 11) and without (n = 17) estrogen receptor-positive breast cancer. Estrone (E-1) was the predominant estrogen in premenopausal breast adipose tissue, and E-1 and mRNA expression of CYP19A1 in adipose tissue correlated positively with BMI. Adipose tissue estradiol (E-2) concentrations fluctuated during the menstrual cycle, similarly to the serum concentrations. In women with breast cancer median adipose tissue E-1 (1519 vs. 3244, p <.05) and E-2 (404 vs. 889 pmol/kg, p <.05) levels were lower in the follicular than in the luteal phase whereas in control women no significant differences were observed. In the follicular phase, mRNA expressions of HSD17B1 (median 0.06; interquartile range 0.05-0.07 vs. 0.17; 0.03-0.2, p = .010) and CYP19A1 (0.08; 0.07-0.14 vs. 0.22; 0.09-0.54, p = .025) were lower in women with breast cancer than in controls. In conclusion, the changes in adipose tissue E-1 and E-2 concentrations and the estrogen-regulating CYP19A1 and HSD17B1 during the menstrual cycle may be related to dysfunctional local estrogen metabolism in women with breast cancer.Peer reviewe