Medium-chain-length polyprenol (C45–C55) formation in chloroplasts of Arabidopsis is brassinosteroid-dependent

Brassinosteroids are important plant hormones influencing, among other processes, chloroplast development, the electron transport chain during light reactions of photosynthesis, and the Calvin-Benson cycle. Medium-chainlength polyprenols built of 9–11 isoprenoid units (C45–C55 carbons) are a class of isoprenoid compounds present in abundance in thylakoid membranes. They are synthetized in chloroplast by CPT7 gene from Calvin cycle derived precursors on MEP methylerythritol 4-phosphate) isoprenoid biosynthesis pathway. C45–C55 polyprenols affect thylakoid membrane ultra-structure and hence influence photosynthetic apparatus performance in plants such as Arabidopsis and tomato. So far nothing is known about the hormonal or environmental regulation of CPT7 gene expression. The aim of our study was to find out if medium-chain-length polyprenol biosynthesis in plants may be regulated by hormonal cues.We found that the CPT7 gene in Arabidopsis has a BZR1 binding element (brassinosteroid dependent) in its promoter. Brassinosteroid signaling mutants in Arabidopsis accumulate a lower amount of medium-chain-length C45–C55 polyprenols than control plants. At the same time carotenoid and chlorophyll content is increased, and the amount of PsbD1A protein coming from photosystem II does not undergo a significant change. On contrary, treatment of WT plants with epi-brassinolide increases C45–C55 polyprenols content. We also report decreased transcription of MEP enzymes (besides C45–C55 polyprenols, precursors of numerous isoprenoids, e.g. phytol, carotenoids are derived from this pathway) and genes encoding biosynthesis of medium-chain-length polyprenol enzymes in brassinosteroid perception mutant bri1-116. Taken together, we document that brassinosteroids affect biosynthetic pathway of C45–C55 polyprenols

Rab-dependent vesicular traffic affects female gametophyte development in Arabidopsis

Eukaryotic cells rely on the accuracy and efficiency of vesicular traffic. In plants, disturbances in vesicular trafficking are well studied in quickly dividing root meristem cells or polar growing root hairs and pollen tubes. The development of the female gametophyte, a unique haploid reproductive structure located in the ovule, has received far less attention in studies of vesicular transport. Key molecules providing the specificity of vesicle formation and its subsequent recognition and fusion with the acceptor membrane are Rab proteins. Rabs are anchored to membranes by covalently linked geranylgeranyl group(s) that are added by the Rab geranylgeranyl transferase (RGT) enzyme. Here we show that Arabidopsis plants carrying mutations in the gene encoding the β-subunit of RGT (rgtb1) exhibit severely disrupted female gametogenesis and this effect is of sporophytic origin. Mutations in rgtb1 lead to internalization of the PIN1 and PIN3 proteins from the basal membranes to vesicles in provascular cells of the funiculus. Decreased transport of auxin out of the ovule is accompanied by auxin accumulation in tissue surrounding the growing gametophyte. In addition, female gametophyte development arrests at the uni- or binuclear stage in a significant portion of the rgtb1 ovules. These observations suggest that communication between the sporophyte and the developing female gametophyte relies on Rab-dependent vesicular traffic of the PIN1 and PIN3 transporters and auxin efflux out of the ovule

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Rab geranylgeranyl transferase β subunit is essential for male fertility and tip growth in Arabidopsis

Rab proteins, key players in vesicular transport in all eukaryotic cells, are post-translationally modified by lipid moieties. Two geranylgeranyl groups are attached to the Rab protein by the heterodimeric enzyme Rab geranylgeranyl transferase (RGT) αβ. Partial impairment in this enzyme activity in Arabidopsis, by disruption of the AtRGTB1 gene, is known to influence plant stature and disturb gravitropic and light responses. Here it is shown that mutations in each of the RGTB genes cause a tip growth defect, visible as root hair and pollen tube deformations. Moreover, FM 1–43 styryl dye endocytosis and recycling are affected in the mutant root hairs. Finally, it is demonstrated that the double mutant, with both AtRGTB genes disrupted, is non-viable due to absolute male sterility. Doubly mutated pollen is shrunken, has an abnormal exine structure, and shows strong disorganization of internal membranes, particularly of the endoplasmic reticulum system

POLYPRENOL REDUCTASE2 Deficiency Is Lethal in Arabidopsis Due to Male Sterility

Dolichol is a required cofactor for protein glycosylation, the most common posttranslational modification modulating the stability and biological activity of proteins in all eukaryotic cells. We have identified and characterized two genes, PPRD1 and -2, which are orthologous to human SRD5A3 (steroid 5α reductase type 3) and encode polyprenol reductases responsible for conversion of polyprenol to dolichol in Arabidopsis thaliana. PPRD1 and -2 play dedicated roles in plant metabolism. PPRD2 is essential for plant viability; its deficiency results in aberrant development of the male gametophyte and sporophyte. Impaired protein glycosylation seems to be the major factor underlying these defects although disturbances in other cellular dolichol-dependent processes could also contribute. Shortage of dolichol in PPRD2-deficient cells is partially rescued by PPRD1 overexpression or by supplementation with dolichol. The latter has been discussed as a method to compensate for deficiency in protein glycosylation. Supplementation of the human diet with dolichol-enriched plant tissues could allow new therapeutic interventions in glycosylation disorders. This identification of PPRD1 and -2 elucidates the factors mediating the key step of the dolichol cycle in plant cells which makes manipulation of dolichol content in plant tissues feasible

Asymptomatic neuroendocrine tumor of the ileocecal area in a 59 year-old patient – a case study

Jedną z częstszych lokalizacji guzów neuroendokrynnych (Neuroendocrine Tumors, NET) przewodu pokarmowego jest jelito cienkie. W większości przypadków są to nowotwory wysoko zróżnicowane o powolnym tempie wzrastania i stanowią wyzwanie diagnostyczne dla gastroenterologów, radiologów i patomorfologów. Z klinicznego punktu widzenia NET jelita cienkiego mogą być nieczynne hormonalnie lub produkować substancje odpowiedzialne za powstawanie charakterystycznych objawów. Czułym, lecz niespecyficznym markerem tych zmian jest stężenie chromograniny A. Podstawę diagnostyki stanowią techniki obrazowe, pozwalające na lokalizację guza oraz endoskopowe, umożliwiające pobranie materiału do badania histopatologicznego i immunohistochemicznego. Chirurgiczne usunięcie zmiany jest leczeniem z wyboru, natomiast w farmakoterapii NET znajdują zastosowanie analogii somatostatyny, terapia radioizotopowa i chemioterapia. Przedstawiamy przypadek asymptomatycznego guza neuroendokrynnego zlokalizowanego w okolicy krętniczo-kątniczej u 59-letniego chorego.One of the more common locations of neuroendocrine tumors (Neuroendocrine Tumors, NET) of the gastrointestinal tract is the small intestine. In the majority of cases, these are slow to develop, highly differentiated tumors, which pose a diagnostic challenge to gastroenterologists, radiologists and pathologists. From the clinical viewpoint, NETs of the small intestine may be hormonally inactive or produce substances responsible for the occurrence of characteristic clinical symptoms. The serum concentration of chromogranin A is a sensitive, yet nonspecific, marker of such changes. The basic method of diagnosing is through the use of imaging techniques, which allow for the location of the tumor; and endoscopic techniques, which permit the extraction of a tissue sample for histopathology and immunohistochemistry ancillary tests. Surgical excision of a lesion is the treatment of choice. However, if pharmacotherapy is employed, the somatostatin analogs, radioisotope therapy and chemotherapy is used. We present a case study, of an asymptomatic neuroendocrine tumor of the ileocecal area, in a 59 year-old male patient

Segmentacja konsumentów wołowiny w Polsce

In their article, the authors presented the results of survey carried out among consumers of beef. They presented the factors affecting consumption of beef, taking into account the quality aspects and culinary preferences, the present places of purchases of beef and perceived purchasing barriers.В статье представлены результаты исследования, проведенного среди потребителей говядины. Представляются факторы, влияющие на потребление говядины, с учетом качественных аспектов и кулинарных предпочтений, актуальные места покупки говядины и воспринимаемые барьеры для покупок