Persistent ER Stress Induces the Spliced Leader RNA Silencing Pathway (SLS), Leading to Programmed Cell Death in Trypanosoma brucei

Trypanosomes are parasites that cycle between the insect host (procyclic form) and mammalian host (bloodstream form). These parasites lack conventional transcription regulation, including factors that induce the unfolded protein response (UPR). However, they possess a stress response mechanism, the spliced leader RNA silencing (SLS) pathway. SLS elicits shut-off of spliced leader RNA (SL RNA) transcription by perturbing the binding of the transcription factor tSNAP42 to its cognate promoter, thus eliminating trans-splicing of all mRNAs. Induction of endoplasmic reticulum (ER) stress in procyclic trypanosomes elicits changes in the transcriptome similar to those induced by conventional UPR found in other eukaryotes. The mechanism of up-regulation under ER stress is dependent on differential stabilization of mRNAs. The transcriptome changes are accompanied by ER dilation and elevation in the ER chaperone, BiP. Prolonged ER stress induces SLS pathway. RNAi silencing of SEC63, a factor that participates in protein translocation across the ER membrane, or SEC61, the translocation channel, also induces SLS. Silencing of these genes or prolonged ER stress led to programmed cell death (PCD), evident by exposure of phosphatidyl serine, DNA laddering, increase in reactive oxygen species (ROS) production, increase in cytoplasmic Ca2+, and decrease in mitochondrial membrane potential, as well as typical morphological changes observed by transmission electron microscopy (TEM). ER stress response is also induced in the bloodstream form and if the stress persists it leads to SLS. We propose that prolonged ER stress induces SLS, which serves as a unique death pathway, replacing the conventional caspase-mediated PCD observed in higher eukaryotes

Effect of nitrogen fertilization intensity on grain and flour quality of winter wheat cultivars

Materiał do badań stanowiły próby ziarna pszenicy ozimej pochodzące z 3- -letnich doświadczeń polowych przeprowadzonych w Rolniczym Zakładzie Doświadczalnym w Grabowie (51°21’ N; 21°40’ E), należącym do IUNG w Puławach, w latach 2003-2006. Określono wpływ 4 poziomów nawożenia azotem (90, 120, 150, 180 kg N·ha-1) 10 odmian pszenicy ozimej na cechy jakościowe ziarna i mąki. Nawożenie azotem miało niewielki wpływ na cechy fizyczne ziarna i liczbę opadania. Zwiększenie dawki azotu z 90 do 150 kg·ha-1 spowodowało istotny wzrost zawartości białka. Zawartość glutenu i wskaźnik sedymentacji mąki wzrastały po zastosowaniu 180 kg N·ha-1. Poprawę cech farinograficznych (rezystencji i rozmiękczenia ciasta oraz wartości walorymetrycznej) stwierdzono dopiero po zastosowaniu 150 kg N·ha-1. Dalsze zwiększenie dawki – do 180 kg N·ha-1 – pozostało bez wpływu na cechy farinograficzne. Wystąpiła istotna interakcja pomiędzy nawożeniem azotem a odmianami w przypadku sedymentacji mąki, rezystencji ciasta i wartości walorymetrycznej. Odmiany o najlepszej jakości znacznie silniej reagowały na nawożenie niż odmiany o gorszych parametrach jakościowych. U odmian typu paszowego (Symfonia i Kaja) brak było różnic w wartościach wyżej wymienionych cech niezależnie od zastosowanej dawki azotu.The material for investigation were grain samples of winter wheat obtained from a 3-years field experiment conducted in the Experimental Station Grabów (51o21’ N; 21o40’ E) of IUNG Puławy in 2003-2006. The effect of 4 nitrogen fertilization levels (90, 120, 150, 180 kg N·ha-1) and 10 cultivars of winter wheat on quality features of grain was estimated. Nitrogen fertilization had an unimportant effect on physical properties of grain and falling number. Increasing the nitrogen dose from 90 to 150 kg·ha-1 caused a significant increase in protein content. Gluten content and value of Zeleny test increased after 180 kg·ha-1 of nitrogen application. Improvement of farinograph properties (dough resistance, dough weakening and valorimeter value) was noticed when the nitrogen dose was 150 kg·ha-1. Further increase in the dose to 180 kg·ha-1 had no influence on farinograph traits. Significant interactions between nitrogen fertilization and cultivars were noticed for Zeleny test, dough resistance an valorimeter value. The reaction for fertilization of the best quality cultivars was much stronger than that of the worse quality cultivars. For the cultivars from the fodder group (Symfonia and Kaja), there were no differences in the above mentioned traits irrespective of the nitrogen doses