Krystyna Oracz

Warsaw University of Life Sciences, Plant Physiology, Faculty Member

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I am a leader of the SeedExplorerGroup (www.seedexplorer.eu) at WULS-SGGW in Warsaw (Poland). I am aware about the important recent advances in seed biology. With my group we elucidate the molecular mechanisms of regulation of seed germination and dormancy, with a focus on the role of Reactive Oxygen Species (ROS) and phytohormones.
Since 2015 I am also a Secretary of the Plant Oxygen Group http://www.plantoxygengroup.org/.

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Papers by Krystyna Oracz

The interaction between miR165/166 and miR160 regulates Arabidopsis thaliana seed size, weight, and number in a ROS-dependent manner.

by Natalia Pawłasek and Krystyna Oracz

PLANTA, 2024

The cycle of plant life and its yield productivity depends fundamentally on the establishment of ... more The cycle of plant life and its yield productivity depends fundamentally on the establishment of the trade-offs of seed size, weight, and number. For annual plants, seed number should simply be a positive function of vegetative biomass and a negative function of seed size and/or weight. However, extensive natural variation within species is observed for these
traits, for which an optimal solution is environmentally dependent. Understanding the miRNA-mediated post-transcriptional regulation of gene expression determining seed phenotype and number is crucial from both an evolutionary and applied perspective. Although extensive research has concentrated on the individual roles of miRNAs in plant life, fewer studies have centred on their functional interactions, hence this study aimed to examine whether the module of miR165/miR166 and/or
miR160 interactions is involved in forming Arabidopsis thaliana seeds, and/or has an impact on their features. Considering that reactive oxygen species (ROS) are among key players in seed-related processes, it was also intriguing to verify if the mechanism of action of these miRNAs is associated with the ROS pathway. The plant material used in this study consisted of flower buds, green siliques, and freshly harvested seeds, of wild type (WT), and STTM165/166 and STTM160 × 165/166 mutants of A. thaliana plants which are powerful tools for functional analysis of miRNAs in plants. The novel results obtained during physiological phenotyping together with two-tailed qRT-PCR analysis of mature miR165, miR166, miR160, and spectrofluorimetric measurement of apoplastic hydrogen peroxide (H2O2) for the first time revealed that interaction between
miR165/miR166 and miR160 may regulate seed size, weight and number in ROS-dependent manner.

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Oxidative stress in germinating mustard seeds [Sinapis alba L.] induced by sunflower allelopathic compounds

Polish Journal of Natural Sciences. Supplement, 2003

Białka ARGONAUT w biologii komórki i rozwoju roślin

Postępy Biochemii

Białka ARGONAUT (AGO) są integralnymi elementami regulatorowych szlaków znajdujących się pod kont... more Białka ARGONAUT (AGO) są integralnymi elementami regulatorowych szlaków znajdujących się pod kontrolą małych RNA (ang. small RNA, sRNA), o fundamentalnym znaczeniu dla właściwego funkcjonowania komórek eukariotycznych. AGO, jako wysoce wyspecjalizowane platformy wiążące specyficzne sRNA, koordynują wyciszanie genów poprzez interakcję z innymi czynnikami białkowymi (tworząc tzw. kompleks RISC, ang. RNA-induced silencing complex), przyczyniając się do endonukleolitycznego cięcia docelowego mRNA i/lub wpływając na proces translacji. Coraz więcej dowodów potwierdza również udział białek AGO w kilku innych procesach komórkowych, takich jak np.: regulacja transkrypcji, sekwestracja, zależna od RNA metylacja DNA, naprawa uszkodzeń DNA, synteza siRNA niezależna od białek DCL (ang. DICER-like), czy też kotranskrypcyjna regulacja ekspresji genów MIRNA i splicingu intronów. Poszczególne gatunki roślin charakteryzują się obecnością różnej liczby białek AGO, w wielu przypadkach o nieznanej jeszc...

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The novel activity of Argonautes in intron splicing: A transcriptome-wide survey in plants

Journal of Plant Physiology, 2022

The importance of the evolutionarily conserved Argonaute (AGO) proteins has been well recognized ... more The importance of the evolutionarily conserved Argonaute (AGO) proteins has been well recognized for their involvement in the RNA interference pathways. Recent discoveries in animals demonstrated that AGOs also participate in alternative splicing (AS). Motivated by the question whether the AGO proteins are also functional in RNA splicing in plants, we searched for the introns excised through an AGO-dependent manner in Arabidopsis (Arabidopsis thaliana). RNA sequencing (RNA-seq) data analysis uncovered hundreds of the introns up- or down-regulated in the ago1 and ago4 mutants, respectively. For different genes, AGOs might play either a positive or a negative role in intron excision, which was further validated by reverse transcription-polymerase chain reaction (RT-PCR). Some introns were specifically regulated by one of the AGO proteins, while some were regulated by both AGOs. Besides, a large portion of the AGO-dependent introns were organ-specifically regulated. RNA immunoprecipitation combined with high-throughput sequencing (RIP-seq) revealed that both AGOs preferentially bound to the intronic regions, supporting their high intron binding affinities. Immunoprecipitation followed by mass spectrometry (IP-MS) was performed to identify the proteins potentially interacting with the two AGOs. Six novel interactors (two interacting with AGO1 and four with both AGOs) involved in mRNA binding were uncovered, which might facilitate AGO-intron recognition. Analysis of the RNA-seq data from the rice (Oryza sativa) ago18 mutants revealed that hundreds of the introns were expressed in an AGO18-dependent manner. In summary, our results point to the novel role of the plant AGOs in intron splicing, paving a way for further studies on the mechanisms underlying AGO-mediated RNA splicing.

With Ethylene Signalling Pathway

This paper is available online free of all access charges (see

Co-tutelle doctoral thesis realized during

Regulatory role of hydrogen cyanide in dormancy removal of sunflower (Helianthus annuus L.) embryos

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Impact of priming process on ROS concentration and the activity of enzymatic antioxidant system in sugar beet ( Beta vulgaris ) seeds

Biotechnologia. Journal of Biotechnology, Computational Biology and Bionanotechnology, 2013

Rola białek modyfikujących strukturę ściany komórkowej w regulacji kiełkowania nasion

Postepy Biologii Komorki, 2016

Streszczenie: Ściana komórkowa jest bardzo dynamiczną strukturą, nieustannie modyfikowaną w trakc... more Streszczenie: Ściana komórkowa jest bardzo dynamiczną strukturą, nieustannie modyfikowaną w trakcie całego cyklu życiowego roślin. Zmiany przebiegające w ścianie komórkowej odgrywają istotne znaczenie również w procesach zachodzących w kiełkujących nasionach. Modulowanie struk-tury ściany komórek bielma okrywającego zarodek jak i wydłużającego się elongacyjnie korzenia zarodkowego ma decydujący wpływ na to czy proces kiełkowania zostanie pomyślnie zakończony. W przebudowie roślinnej ściany komórkowej biorą udział między innymi specyficzne białka mody-fikujące polisacharydy (ang. Cell Wall Remodeling Proteins, CWRP), wchodzące w skład tej struk-tury komórkowej, takie jak: fibryle celulozowe, hemicelulozy oraz pektyny. W niniejszym artykule zgromadzono aktualne informacje na temat roli wybranych CWRP uczestniczących w modelowaniu struktury pierwotnej ściany komórkowej kiełkujących nasion, takich jak: 1) celulazy (CEL) – roz-kładające celulozę, 2) hemicelulazy mannolityczne (np. mannanazy, MAN) oraz ksylanolityczne (np. endotransglikozylazy/hydrolazy ksyloglukanowe, XTH) – odpowiedzialne za hydrolizę hemiceluloz, 3) liazy pektynianowe (liazy PGA), a także metyloesterazy pektynowe (PME) i poligalakturonazy (PG), które wspólnie odpowiadają za rozkład pektyn. Omówiono również udział ekspansyn (EXP) – białek o niepotwierdzonej dotychczas aktywności enzymatycznej, ale mimo to istotnym znaczeniu w procesie rozluźniania i relaksacji ściany komórkowej podczas wzrostu komórek i tkanek roślin. Po-dano także przykłady wpływu hormonów roślinnych, takich jak: gibereliny (GA), kwas abscysynowy (ABA) i etylen (ET) na ekspresję i/lub aktywność niektórych z CWRP w kiełkujących nasionach. In-formacje przedstawione w tym artykule przeglądowym podkreślają rolę modyfikacji struktury ściany komórkowej przez CWRP, jako jednego z kluczowych mechanizmów wpływających na zależne od sygnałów hormonalnych procesy zachodzące w nasionach. Słowa kluczowe: białka modyfikujące ścianę komórkową, kiełkowanie nasion, polisacharydy, roś-linna ściana komórkowa

phyB and HY5 are Involved in the Blue Light-Mediated Alleviation of Dormancy of Arabidopsis Seeds Possibly via the Modulation of Expression of Genes Related to Light, GA, and ABA

International Journal of Molecular Sciences, 2019

Light is one of the most important environmental factors regulating seed germination. It is known... more Light is one of the most important environmental factors regulating seed germination. It is known that light inhibits seed germination of some monocotyledonous species and that it is mostly related to the blue wavelength of the spectrum received by cryptochromes (cry). Research has also found that the red light (R) stimulates germination of dicotyledonous seeds and that this reaction involves mainly phytochromes (phy). Surprisingly, up to date, the role and the mechanism of action of blue light (BL) in seed biology of dicot plants is still very poorly understood and some questions are unexplained, e.g., whether BL plays a role in regulation of dicot seeds dormancy and/or germination? If, so what particular elements of light signaling pathway are involved in modulation of this(ese) process(es)? Also, is the BL action in regulation of dicot seeds dormancy and/or germination maybe due to changes of expression of genes related to metabolism and/or signaling of two phytohormones controll...

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Cellular Recycling of Proteins in Seed Dormancy Alleviation and Germination

Frontiers in Plant Science, 2016

Each step of the seed-to-seed cycle of plant development including seed germination is characteri... more Each step of the seed-to-seed cycle of plant development including seed germination is characterized by a specific set of proteins. The continual renewal and/or replacement of these biomolecules are crucial for optimal plant adaptation. As proteins are the main effectors inside the cells, their levels need to be tightly regulated. This is partially achieved by specific proteolytic pathways via multicatalytic protease complexes defined as 20S and 26S proteasomes. In plants, the 20S proteasome is responsible for degradation of carbonylated proteins, while the 26S being a part of ubiquitin-proteasome pathway is known to be involved in proteolysis of phytohormone signaling regulators. On the other hand, the role of translational control of plant development is also well-documented, especially in the context of pollen tube growth and light signaling. Despite the current progress that has been made in seed biology, the sequence of cellular events that determine if the seed can germinate or not are still far from complete understanding. The role and mechanisms of regulation of proteome composition during processes occurring in the plant's photosynthetic tissues have been well-characterized since many years, but in non-photosynthetic seeds it has emerged as a tempting research task only since the last decade. This review discusses the recent discoveries providing insights into the role of protein turnover in seed dormancy alleviation, and germination, with a focus on the control of translation and proteasomal proteolysis. The presented novel data of translatome profiling in seeds highlighted that post-transcriptional regulation of germination results from a timely regulated initiation of translation. In addition, the importance of 26S proteasome in the degradation of regulatory elements of cellular signaling and that of the 20S complex in proteolysis of specific carbonylated proteins in hormonal-and light-dependent processes occurring in seeds is discussed. Based on the current knowledge the model of cellular recycling of proteins in germinating seeds is also proposed.

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Phytohormones Signaling Pathways and ROS Involvement in Seed Germination

Frontiers in Plant Science, 2016

Phytohormones and reactive oxygen species (ROS) are major determinants of the regulation of devel... more Phytohormones and reactive oxygen species (ROS) are major determinants of the regulation of development and stress responses in plants. During life cycle of these organisms, signaling networks of plant growth regulators and ROS interact in order to render an appropriate developmental and environmental response. In plant's photosynthetic (e.g., leaves) and non-photosynthetic (e.g., seeds) tissues, enhanced and suboptimal ROS production is usually associated with stress, which in extreme cases can be lethal to cells, a whole organ or even an organism. However, controlled production of ROS is appreciated for cellular signaling. Despite the current progress that has been made in plant biology and increasing number of findings that have revealed roles of ROS and hormonal signaling in germination, some questions still arise, e.g., what are the downstream protein targets modified by ROS enabling stimulus-specific cellular responses of the seed? Or which molecular regulators allow ROS/phytohormones interactions and what is their function in seed life? In this particular review the role of some transcription factors, kinases and phosphatases is discussed, especially those which usually known to be involved in ROS and hormonal signal transduction under stress in plants, may also play a role in the regulation of processes occurring in seeds. The summarized recent findings regarding particular ROS-and phytohormonesrelated regulatory proteins, as well as their integration, allowed to propose a novel, possible model of action of LESION SIMULATING DISEASE 1, ENHANCED DISEASE SUSCEPTIBILITY 1, and PHYTOALEXIN DEFICIENT 4 functioning during seeds life.

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Phytotoxic effects of sunflower (Helianthus annuus L.) leaf extracts on germinating mustard (Sinapis alba L.) seeds

Allelopathy Journal

Sunflower (Heliantus annuus L.) foliar extract inhibited the germination of mustard (Sinapis alba... more Sunflower (Heliantus annuus L.) foliar extract inhibited the germination of mustard (Sinapis alba L.) seeds. It was accompanied by increased membrane deterioration and enhanced H2O2 production. ABA concentration increased in seeds imbibed in the presence of sunflower phytotoxins, whereas ethylene production was inhibited. Activity of key enzymes of ethylene biosynthetic pathway: ACC synthase and ACC oxidase in seeds treated by sunflower extract was decreased. Sunflower phytotoxins seems to disturb the hormonal balance between ABA and ethylene, which is regarded as the factor controlling the germination of seeds and growth of young seedlings.

Involvement of oxidative stress and ABA in CN-mediated elimination of embryonic dormancy in apple

The biology of seeds: recent research advances. Proceedings of the Seventh International Workshop on Seeds, Salamanca, Spain, 2002

ROS production and protein oxidation as a novel mechanism for seed dormancy alleviation

The Plant Journal, 2007

At harvest, sunflower (Helianthus annuus L.) seeds are dormant and unable to germinate at tempera... more At harvest, sunflower (Helianthus annuus L.) seeds are dormant and unable to germinate at temperatures below 15°C. Seed storage in the dry state, known as after-ripening, is associated with an alleviation of embryonic dormancy allowing subsequent germination at suboptimal temperatures. To identify the process by which dormancy is broken during after-ripening, we focused on the role of reactive oxygen species (ROS) in this phenomenon. After-ripening entailed a progressive accumulation of ROS, namely superoxide anions and hydrogen peroxide, in cells of embryonic axes. This accumulation, which was investigated at the cellular level by electron microscopy, occurred concomitantly with lipid peroxidation and oxidation (carbonylation) of specific embryo proteins. Incubation of dormant seeds for 3 h in the presence of hydrogen cyanide (a compound that breaks dormancy) or methylviologen (a ROS-generating compound) also released dormancy and caused the oxidation of a specific set of embryo proteins. From these observations, we propose a novel mechanism for seed dormancy alleviation. This mechanism involves ROS production and targeted changes in protein carbonylation patterns.

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The Mechanisms Involved in Seed Dormancy Alleviation by Hydrogen Cyanide Unravel the Role of Reactive Oxygen Species as Key Factors of Cellular Signaling during Germination

Plant Physiology, 2009

The physiological dormancy of sunflower (Helianthus annuus) embryos can be overcome during dry st... more The physiological dormancy of sunflower (Helianthus annuus) embryos can be overcome during dry storage (after-ripening) or by applying exogenous ethylene or hydrogen cyanide (HCN) during imbibition. The aim of this work was to provide a comprehensive model, based on oxidative signaling by reactive oxygen species (ROS), for explaining the cellular mode of action of HCN in dormancy alleviation. Beneficial HCN effect on germination of dormant embryos is associated with a marked increase in hydrogen peroxide and superoxide anion generation in the embryonic axes. It is mimicked by the ROS-generating compounds methylviologen and menadione but suppressed by ROS scavengers. This increase results from an inhibition of catalase and superoxide dismutase activities and also involves activation of NADPH oxidase. However, it is not related to lipid reserve degradation or gluconeogenesis and not associated with marked changes in the cellular redox status controlled by the glutathione/glutathione d...

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Myrigalone A Inhibits Lepidium sativum Seed Germination by Interference with Gibberellin Metabolism and Apoplastic Superoxide Production Required for Embryo Extension Growth and Endosperm Rupture

Plant and Cell Physiology, 2011

Myrica gale L. (sweet gale) fruit leachate contains myrigalone A (MyA), a rare C-methylated dihyd... more Myrica gale L. (sweet gale) fruit leachate contains myrigalone A (MyA), a rare C-methylated dihydrochalcone and putative allelochemical, which is known to be a phytotoxin impeding seedling growth. We found that MyA inhibited Lepidium sativum L. seed germination in a dose-dependent manner. MyA did not affect testa rupture, but inhibited endosperm rupture and the transition to subsequent seedling growth. MyA inhibited micropylar endosperm cap (CAP) weakening and the increase in the growth potential of the radical/hypocotyl region (RAD) of the embryo, both being key processes required for endosperm rupture. We compared the contents of abscisic acid (ABA) and gibberellins in the tissues and found that the major bioactive forms of gibberellin in L. sativum seed tissues were GA 4 and GA 6 , while GA 8 and GA 13 were abundant inactive metabolites. MyA did not appreciably affect the ABA contents, but severely interfered with gibberellin metabolism and signaling by inhibiting important steps catalyzed by GA3 oxidase, as well as by interfering with the GID1-type gibberellin signaling pathway. The hormonally and developmentally regulated formation of apoplastic superoxide radicals is important for embryo growth. Specific zones within the RAD were associated with accumulation of apoplastic superoxide radicals and endoreduplication indicative of embryo cell extension. MyA negatively affected both of these processes and acted as a scavenger of apoplastic reactive oxygen species. We propose that MyA is an allelochemical with a novel mode of action on seed germination.

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Release of sunflower seed dormancy by cyanide: cross-talk with ethylene signalling pathway

Journal of Experimental Botany, 2008

Freshly harvested sunflower (Helianthus annuus L.) seeds are considered to be dormant because the... more Freshly harvested sunflower (Helianthus annuus L.) seeds are considered to be dormant because they fail to germinate at relatively low temperatures (10°C). This dormancy results mainly from an embryo dormancy and disappears during dry storage. Although endogenous ethylene is known to be involved in sunflower seed alleviation of dormancy, little attention had been paid to the possible role of cyanide, which is produced by the conversion of 1-aminocyclopropane 1-carboxylic acid to ethylene, in this process. The aims of this work were to investigate whether exogenous cyanide could improve the germination of dormant sunflower seeds and to elucidate its putative mechanisms of action. Naked dormant seeds became able to germinate at 10°C when they were incubated in the presence of 1 mM gaseous cyanide. Other respiratory inhibitors showed that this effect did not result from an activation of the pentose phosphate pathway or the cyanide-insensitive pathway. Cyanide stimulated germination of dormant seeds in the presence of inhibitors of ethylene biosynthesis, but its improving effect required functional ethylene receptors. It did not significantly affect ethylene production and the expression of genes involved in ethylene biosynthesis or in the first steps of ethylene signalling pathway. However, the expression of the transcription factor Ethylene Response Factor 1 (ERF1) was markedly stimulated in the presence of gaseous cyanide. It is proposed that the mode of action of cyanide in sunflower seed dormancy alleviation does not involve ethylene production and that ERF1 is a common component of the ethylene and cyanide signalling pathways.

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Large-Scale Phenomics Identifies Primary and Fine-Tuning Roles for CRKs in Responses Related to Oxidative Stress

PLOS Genetics, 2015

Cysteine-rich receptor-like kinases (CRKs) are transmembrane proteins characterized by the presen... more Cysteine-rich receptor-like kinases (CRKs) are transmembrane proteins characterized by the presence of two domains of unknown function 26 (DUF26) in their ectodomain. The CRKs form one of the largest groups of receptor-like protein kinases in plants, but their biological functions have so far remained largely uncharacterized. We conducted a large-scale phenotyping approach of a nearly complete crk T-DNA insertion line collection showing that CRKs control important aspects of plant development and stress adaptation in response to biotic and abiotic stimuli in a non-redundant fashion. In particular, the analysis of reactive PLOS Genetics |

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Białka ARGONAUT w biologii komórki i rozwoju roślin

by Anna Sokołowska, Maciej Rugała, and Krystyna Oracz

Postępy Biochemii, 2022

Białka ARGONAUT (AGO) są integralnymi elementami regulatorowych szlaków znajdujących się pod kont... more Białka ARGONAUT (AGO) są integralnymi elementami regulatorowych szlaków znajdujących się pod kontrolą małych RNA (ang. small RNA, sRNA), o fundamentalnym znaczeniu dla właściwego funkcjonowania komórek eukariotycznych. AGO, jako wysoce wyspecjalizowane platformy wiążące specyficzne sRNA, koordynują wyciszanie genów poprzez interakcję z innymi czynnikami białkowymi (tworząc tzw. kompleks RISC, ang. RNA--induced silencing complex), przyczyniając się do endonukleolitycznego cięcia docelowego mRNA i/lub wpływając na proces translacji. Coraz więcej dowodów potwierdza również
udział białek AGO w kilku innych procesach komórkowych, takich jak np.: regulacja transkrypcji, sekwestracja, zależna od RNA metylacja DNA, naprawa uszkodzeń DNA, synteza siRNA niezależna od białek DCL (ang. DICER-like), czy też kotranskrypcyjna regulacja ekspresji genów MIRNA i splicingu intronów. Poszczególne gatunki roślin charakteryzują się
obecnością różnej liczby białek AGO, w wielu przypadkach o nieznanej jeszcze regulatorowej i/lub biologicznej funkcji. Niniejszy artykuł przeglądowy obejmuje aktualną wiedzę na temat funkcji roślinnych AGO w biologii komórki i rozwoju roślin.

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Induction of Oxidative Stress by Sunflower Phytotoxins in Germinating Mustard Seeds

The aim of this study was to investigate the phytotoxic effect of sunflower on physiological and ... more The aim of this study was to investigate the phytotoxic effect of sunflower on physiological and biochemical processes during germination of mustard seeds (Sinapis alba L. cv. Nakielska). To exclude the involvement of osmotic stress in seed reaction to phytotoxic compounds, we compared the effect of 10 % (w/v) water extract from sunflower (Helianthus annuus L. cv. Ogrodowy) leaves and 28.4 % (w/v) polyethylene glycol (PEG) 8000 solution characterized by an equal Y =−1 MPa. We evaluated (1) the amount of hydrogen peroxide (H2O2); (2) activities of antioxidant enzymes: superoxide dismutase, catalase, and glutathione reductase; (3) membrane permeability; and (4) level of malondialdehyde (MDA). Both, sunflower compounds and PEG solutions inhibited mustard seed germination, but only phytotoxins caused an increase in the cell membrane permeability, MDA level, H2O2 concentration, and alterations in activities of antioxidant enzymes. Our results demonstrate that despite the activation of th...

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