MicroRNAs are intensively regulated during induction of somatic embryogenesis in Arabidopsis

Several genes encoding transcription factors (TFs) were indicated to have a key role in the induction of somatic embryogenesis (SE), which is triggered in the somatic cells of plants. In order to further explore the genetic regulatory network that is involved in the embryogenic transition induced in plant somatic cells, micro-RNA (miRNAs) molecules, the products of MIRNA (MIR) genes and the common regulators of TF transcripts, were analyzed in an embryogenic culture of Arabidopsis thaliana. In total, the expression of 190 genes of the 114 MIRNA families was monitored during SE induction and the levels of the primary (pri-miRNAs) transcripts vs. the mature miRNAs were investigated. The results revealed that the majority (98%) of the MIR genes were active and that most of them (64%) were differentially expressed during SE. A distinct attribute of the MIR expression in SE was the strong repression of MIR transcripts at the early stage of SE followed by their significant up-regulation in the advanced stage of SE. Comparison of the mature miRNAs vs. pri-miRNAs suggested that the extensive post-transcriptional regulation of miRNA is associated with SE induction. Candidate miRNA molecules of the assumed function in the embryogenic response were identified among the mature miRNAs that had a differential expression in SE, including miR156, miR157, miR159, miR160, miR164, miR166, miR169, miR319, miR390, miR393, miR396, and miR398. Consistent with the central role of phytohormones and stress factors in SE induction, the functions of the candidate miRNAs were annotated to phytohormone and stress responses. To confirm the functions of the candidate miRNAs in SE, the expression patterns of the mature miRNAs and their presumed targets were compared and regulatory relation during SE was indicated for most of the analyzed miRNA-target pairs. The results of the study contribute to the refinement of the miRNA-controlled regulatory pathways that operate during embryogenic induction in plants and provide a valuable platform for the identification of the genes that are targeted by the candidate miRNAs in SE induction

mRNA adenosine methylase (MTA) deposits m6A on pri-miRNAs to modulate miRNA biogenesis in Arabidopsis thaliana

Copyright © 2020 the Author(s). Published by PNAS. In Arabidopsis thaliana, the METTL3 homolog, mRNA adenosine methylase (MTA) introduces N6-methyladenosine (m6A) into various coding and noncoding RNAs of the plant transcriptome. Here, we show that an MTA-deficient mutant (mta) has decreased levels of microRNAs (miRNAs) but accumulates primary miRNA transcripts (pri-miRNAs). Moreover, pri-miRNAs are methylated by MTA, and RNA structure probing analysis reveals a decrease in secondary structure within stem-loop regions of these transcripts in mta mutant plants. We demonstrate interaction between MTA and both RNA Polymerase II and TOUGH (TGH), a plant protein needed for early steps of miRNA biogenesis. Both MTA and TGH are necessary for efficient colocalization of the Microprocessor components Dicer-like 1 (DCL1) and Hyponastic Leaves 1 (HYL1) with RNA Polymerase II. We propose that secondary structure of miRNA precursors induced by their MTA-dependent m6A methylation status, together with direct interactions between MTA and TGH, influence the recruitment of Microprocessor to plant pri-miRNAs. Therefore, the lack of MTA in mta mutant plants disturbs pri-miRNA processing and leads to the decrease in miRNA accumulation. Furthermore, our findings reveal that reduced miR393b levels likely contributes to the impaired auxin response phenotypes of mta mutant plants

Functional connections between chromatin structure, RNA Polymerase II processivity and alternative splicing in Arabidopsis thaliana

Wydział Biologii: Instytut Biologii Molekularnej i BiotechnologiiPrzez wiele lat proces transkrypcji oraz dojrzewania RNA rozpatrywane były niezależnie. Ostatnie badania pokazują jednak, że synteza prekursorowych RNA oraz ich obróbka to procesy silnie ze sobą powiązane, które należy rozpatrywać i badać na tle wzajemnych interakcji. Pośród procesów, których mechanizm działania i końcowy efekt jest zależny od struktury chromatyny i tempa transkrypcji przez polimerazę RNA II wymienia się jeden z ważniejszych mechanizmów regulacji ekspresji genów - splicing alternatywny. Mechanizm ten zwiększa potencjał kodujący genomu. Ta sama cząsteczka pre-mRNA jest potencjalnym źródłem kilku różnych dojrzałych mRNA, które mogą powstać na skutek wyboru alternatywnych miejsc splicingowych. U człowieka około 95% genów zawierających introny podlega alternatywnemu splicingowi. W przypadku Arabidopsis thaliana wartość ta oscyluje w granicach 60%. Ponad 75% alternatywnych zdarzeń splicingowych ma miejsce w obrębie sekwencji kodującej genu, co daje potencjalną możliwość generowania białek o zmienionej strukturze i funkcji. W wyniku realizacji projektu, podjęta została próba wykazania kluczowych czynników biorących udział w ko-transkrypcyjnej regulacji splicingu alternatywnego. Do analizy wybrano elementy chromatyny (histon łącznikowy H1.3), białka kompleksu remodelującego chromatynę SWI/SNF, czynnik transkrypcyjny wpływający na tempo polimerazy RNA II (TFIIS) oraz jeden z czynników splicingowych (NTR1). Dla wszystkich wymienionych elementów wykazano wpływ na wycinanie intronów i wybór alternatywnych miejsc splicingowych, co dowodzi słuszności twierdzenia o występowaniu ko-transkrypcyjnego splicingu u roślin.For many years, transcription and RNA maturation have been studied independently. However, data from the past few years shows that the synthesis and processing of the RNA precursor are strongly associated processes that should be considered and examined together. One of the most important mechanisms of gene expression regulation - alternative splicing - is indicated as one of those processes whose mechanism of action and final effect depend on the chromatin structure and RNA Polymerase II elongation rate. Alternative splicing increases the coding potential of the genome. The same pre-mRNA molecule is a potential source of several different mature mRNAs. In humans, approximately 95% of the genes that contain introns are subjected to alternative splicing. In the case of Arabidopsis thaliana, this value is around 60%. More than 75% of the alternative splicing event occurs within the coding sequence of the gene, which provides a potential opportunity to generate proteins with modified structures and functions. During this study, the main goal was to demonstrate the key factors involved of the co-transcriptional regulation of alternative splicing. For the analysis, the following selected proteins were used: components of chromatin (H1.3 linker histone), subunits of chromatin remodeling complex SWI/SNF, the transcription factor regulating RNA Polymerase II elongation (TFIIS), and one of the splicing factors (NTR1). For each of these elements, the effect on the splicing and selection of alternative splicing sites was observed. These results provide proof for co-transcriptional splicing in plants.This work was supported by the Polish National Science Center - NCN (PRELUDIUM 2011/03/N/NZ2/03070), (ETIUDA 2014/12/T/NZ2/00246) and by KNOW RNA Research Center in Poznan (01/KNOW2/2014). Computational part of this study was supported by Poznan Supercomputing and Networking Center - PSNC (grant: 250/2015). The PhD fellowship is part of the International PhD Program 'From genome to phenotype: A multidisciplinary approach to functional genomics' (MPD/2010/3) funded by the Foundation for Polish Science (FNP)

Tribological Properties of Single (AlSi7/SiCp, AlSi7/GCsf) and Hybrid (AlSi7/SiCp + GCsf) Composite Layers Formed in Sleeves via Centrifugal Casting

When designing the composition and structure of a composite material intended for tribological cooperation, many external and structural factors must be considered. The aim of this research was to compare the tribological properties (wear resistance and friction coefficient) of AlSi7Mg1Sr0.03/SiCp and AlSi7Mg1Sr0.03/GCsf single-reinforced composite layers with AlSi7Mg1Sr0.03/SiCp + GCsf hybrid composite layer formed in sleeves via vertical centrifugal casting. Profilometry enabled quantitative and qualitative analyses to be performed on the wear traces formed on investigated surfaces. The results show that a hybrid composite layer containing spherical glassy carbon particles had a significantly lower and more stable coefficient of friction (μ) and a higher wear resistance compared with single composite layers. The obtained effect was related to the mechanism of vitreous carbon consumption, which was crushed during operation, and then introduced between the cooperating friction surfaces. In this way, it acted as a solid lubricant, which stabilized the coefficient of friction and reduced the wear process

Kwietnica okazała Protaetia speciosissima (Scopoli, 1786) (Coleoptera: Scarabaeidae) w skrzynce lęgowej dla puszczyka Strix aluco L., 1758 w Dąbrowach Krotoszyńskich

<p>This paper presents a new record of the rose chafer Protaetia speciosissima (Scopoli, 1786) (Coleoptera: Scarabaeidae), a rare beetle species associated with tree hollows. Specimens of this beetle were found in the oak forest in the Krotoszyn Forest District, west-central Poland, in nest-box for the tawny owl (Strix aluco L., 1758) that had accumulated dead organic material. This finding suggests that it is possible for P. speciosissima to develop and reproduce outside its typical microhabitats.</p&gt

Assessment of the Tribological Properties of Aluminum Matrix Composites Intended for Cooperation with Piston Rings in Combustion Engines

Tribological interactions between the piston groove and ring in combustion engines have a significant influence on mechanical friction losses. Based on the analysis of the distribution of forces acting on the piston, the conditions for the friction tests were selected. The research was carried out on composites reinforced with silicon carbide (SiCp), glassy carbon (GCp), and a hybrid mixture of particles (SiCp + GCp). Tribological tests were carried out under extremely unfavorable dry sliding conditions using a pin-on-block tester. The friction of coefficient and wear values of the matrix alloy, composites, and iron were compared. Profilometry was used to perform quantitative and qualitative analyses of the wear tracks formed on the tested surfaces. The effect of the presence of reinforcing particles on the geometry of working surfaces was also evaluated. The obtained results show that AlSi12CuNiMg/SiCp and AlSi12CuNiMg/SiCp + GCp composites provided satisfactory effects towards stabilizing the friction coefficient and reducing the wear of tested tribological couples. This may provide a new solution dedicated to an important system, which is the piston groove/piston ring in diesel engines

Down-regulation of CBP80 gene expression as a strategy to engineer a drought-tolerant potato

Developing new strategies for crop plants to respond to drought is crucial for their innovative breeding. The down-regulation of nuclear cap-binding proteins in Arabidopsis renders plants drought tolerant. The CBP80 gene in the potato cultivar Desiree was silenced using artificial microRNAs. Transgenic plants displayed a higher tolerance to drought, ABA-hypersensitive stomatal closing, an increase in leaf stomata and trichome density, and compact cuticle structures with a lower number of microchannels. These findings were correlated with a higher tolerance to water stress. The level of miR159 was decreased, and the levels of its target mRNAs MYB33 and MYB101 increased in the transgenic plants subjected to drought. Similar trends were observed in an Arabidopsis cbp80 mutant. The evolutionary conservation of CBP80, a gene that plays a role in the response to drought, suggests that it is a candidate for genetic manipulations that aim to obtain improved water-deficit tolerance of crop plants