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Heavy metal contamination in soil is a global concern due to its harmful effect to all living organisms. Phytoremediation is an emerging cost- effective technology, which utilizes different types of hyperaccumulator plants for the removal of heavy metal pollutants. Crop plants have been suggested as a good candidate for recultivation of agricultural soil in phytoremediation process, however the molecular mechanisms responsible for the crop tolerance to heavy metals is still unknown. Metal-tolerance proteins (MTPs) are divalent cation transporters that play critical roles in metal tolerance and ion homeostasis in plants. The current study identified 12 HvMTPs in the barley (Hordeum vulgare, Hv) genome; the majority of MTPs were hydrophobic proteins found in the vacuolar membrane. Gene expression profiling suggests that HvMTPs play an active role in maintaining barley nutrient homeostasis throughout its life cycle. The expression of barley HvMTP genes in the presence of heavy metals revealed that these MTPs were induced by at least one metal ion, implying their involvement in metal tolerance.

The wax coating is an element of the lipid protective layer, the cuticle, which covers the above-ground organs of plants and is the main barrier that prevents non-stomatal water loss. The cuticle helps protect plant surfaces from pathogens and ultraviolet radiation and influences interactions between plants and insects. The accumulation of cuticular wax is one of the mechanisms of adaptation to drought stress. As a result, there are more and more reports on the relationship between cuticular wax and plant resistance to drought. This article deals with the relationship between cuticular waxes and drought resistance in cereals. The paper presents the achievements to date on (i) the relationship between wax biosynthesis and plant response to drought stress using glaucous and nonglaucous near-isogenic lines and on (ii) investigating the role of genes for cuticular wax biosynthesis and transport and the transcription factors that regulate them using mutants with disrupted wax coat formation.

ARGONAUTE (AGO) proteins are integral parts of regulatory pathways under the control of small RNA (sRNA) that are fundamental for the proper functioning of eukaryotic cells. AGOs, as highly specialized platforms binding specific sRNA, coordinate gene silencing through interaction with other protein factors (forming the RNA-induced silencing complex, RISC), contributing to endonucleolytic cleavage of the target mRNA and/or influencing the translation process. The increasing number of evidence confirms the participation of AGO proteins in several other cellular processes, such as i.e.: transcription regulation, sequestration, RNA-dependent methylation of DNA, repair of DNA damages, synthesis of siRNA independent of DCL (DICER-like) proteins, or co-transcriptional regulation of MIRNA genes expression and intron splicing. Particular plant species are characterized by the presence of a different number of AGO proteins, in many cases of yet unknown regulatory and/or biological function. This review article covers the current knowledge about the functions of AGOs in cell biology and plant development.

Plant cells possess the remarkable ability to adapt to environmental changes. It is manifested by formation of embryos directly from the cells of plant body, bypassing the fertilization stage. These embryo structures develop into complete plants. The process itself, to distinguish the path of formation and emphasize consistency with zygotic embryogenesis, is referred to as somatic embryogenesis (SE). Although more than 60 years have passed since the first publication on the phenomenon has been written, the mechanism of reprogramming of a somatic cell into an embryogenic one is still not fully understood. This is a critical step in SE that can be induced by exo- and endogenous factors and stress treatments. The exposition of plant material to these factors affects the reorganization of the chromatin structure and gene expression, which can consequently trigger the program of embryogenesis. The paper reviews current knowledge on how the identity of totipotent cells is determined and the which stimuli are required to reprogram somatic cell development. Knowledge of key molecular regulators and the network of relationships that control the SE induction is summarized. Issues that are important for enhancing the understanding of the mechanisms underlying totipotency are also defined. Finally, the practical potential of SE is demonstrated, and examples of its use are provided.

Plants possess the ability of indeterminate growth and organogenesis. Uninterrupted development of aerial parts of plants strongly depends on the activity of the shoot apical meristem (SAM), where a pool of undifferentiated stem cells is kept throughout the plant life. The main function of SAM is cell proliferation and self-maintenance. Numerous genes functioning within the SAM have already been discovered, including SHOOTMERISTEMLESS, CLAVATA and WUSCHEL. The biological significance of WUSCHEL gene for specification of the stem cells fate was proven by various, performed over the years experiments. This was doable, also because the research was performed on Arabidopsis thaliana as a model organism. How was the WUSCHEL gene mechanism of action discovered, and subsequently experimentally proven? In this review, we will address these questions, pinpointing also how the use of a model organism enabled WUSCHEL gene functional characterisation.

Hypoxia in plants is a usually the result of heavy rainfall and the subsequent flooding. All current climate models indicate a notable increase in extreme weather over the coming years. Depending on the species and geographical location, plants have developed two distinct strategies for hypoxia stress adaptation: escape and quiescence. The escape strategy involves rapid growth of part of the shoot above the water level whe­reas the second strategy requires a significant reduction in the metabolic rate of the plant in order to survive until the negative environmental conditions pass. These processes are primarily regulated by ethylen in addition to the transcription factor, ERF (ethylen response factor), which enables the transcription of hypoxia response genes. These processes are primarily regulated by ethylen in addition to the transcription factors, ERFs (ethylen response factors), which enables the transcription of hypoxia response genes. Most ERF genes are constitutively trans­cribed independently of oxygen concentration. However, post-translational modification of the N-terminus of ERFs leads to their degradation in plants growing under physiological conditions. During hypoxia there is an increase in the expression level of genes associated with carbon, nitrogen, glycolysis or anaerobic respiration. However, as shown by studies using ribosome profiling, in order to save energy, plants under hypoxic stress strongly inhibit the process of initiating translation. The regulation of gene expression under stress conditions is also influen­ced by the accumulation of poly(A) RNA in the cell nucleus and cytoplasmic stress granules.

Arabidopsis thaliana since a few decades is used as a model for biological and plant genetic research. Natural variation of this species is related to its geographical range which covers different climate zones and habitats. The ability to occupy such a wide area by Arabidopsis is possible due to its stress tolerance and adaptability. Arabidopsis accessions exhibit phenotypic and genotypic variation, which is a result of adaptation to local environmental conditions. During development, plants are subjected to various stress factors. Plants show a spectrum of reactions, processes and phenomena that determine their survival in these adverse conditions. The response of plants to stress involves signal detection and transmission. These reactions are different and depend on the stressor, its intensity, plant species and life strategy. It is assumed that the populations of the same species from different geographical regions acclimated to the stress conditions develop a set of alleles, which allow them to grow and reproduce. Therefore, the study of natural variation in response to abiotic stress among Arabidopsis thaliana accessions allows to find key genes or alleles, and thus the mechanisms by which plants cope with adverse physical and chemical conditions. This paper presents an overview of recent findings, tools and research directions used in the study of natural variation in Arabidopsis thaliana accessions. Additionally, we explain why accessions can be used in the phylogenetic analyses and to study demography and migration of Arabidopsis thaliana.

Transcription factors are proteins that are able to regulate the expression of target genes by specifically binding with DNA sequences and regulating the activity initiation complex of transcription. These proteins are key elements in the adaptation of plants to environmental conditions. Families of transcription factors that are associated with a response to stress are DREB/CBF, AREB/ABF, MYB/MYC and NAC. The NAC gene family is one of the largest families of transcription factors. Members of the NAC family have been identified in many plant species. NAC TFs are involved in the growth, development and response of plants to biotic and abiotic stress. Many transcription factors belonging to the NAC family, including SNAC1, are involved in the response of plants to water deficiency. Drought is the most harmful environmental stress in worldwide agriculture. Obtaining plants with an increased tolerance to water deficiency by using the methods of molecular biology has become a major goal of plant breeding.

Jasmonates are plant hormones involved in many growth and development processes. They also participate in plant defense responses. Current progress in the study on biosynthesis and signaling of jasmonates has contributed to the understanding of the mechanisms regulating concentration of these hormones in the cell. Sustaining a proper level of jasmonates allow the plant to respond appropriately to changing conditions. It is possible due to the large number of enzymes and genes involved in biosynthesis of these hormones as well as multilevel control of their expression.

Micro RNAs are 21-24 nt long RNA molecules involved in the regulation of gene expression on mRNA level. Mature miRNA molecules associated with the RNA-induced silencing complex (RISC) guide specifically mRNA cleavage or inhibit the translation. In plants selective mRNA degradation in miRNA-dependent pathway is a widespread mechanism that occurs more frequently than translation inhibition. miRNA precursors, known as pri-miRNA, are processed in several steps to produce mature miRNA molecules. There are several plant proteins involved in miRNA processing: DCL1, HYL1, SE, HEN1 and HASTY. The role of these proteins is discussed.

In response to long term (at least 1-3 h) irradiance changes the responses are elicited at the level of structure and function of photosynthetic apparatus of plants which are thought to be aimed to keep the balance between the level of excitation energy funneled to the reaction centers of the photosystems by energetic antennae and the utilization of this energy in the form of photosynthetic electron transfer and dark reactions. At high vs medium irradiances the rate of excitation energy transfer via LHCII is reduced while the rate of electron flow and photosynthetic dark reactions is increased. The reaction at LHCII level stems from the reduction of its pool per PSII reaction center and the regulatory events comprise changes in the expression of LHCII apoproteins and/or chi b biosynthesis. The basis for higher electron flow capabilities lies in significant increases in the content of some electron carriers and the catalytic activity of ATP synthase. The upregulation of photosynthetic dark reaction in turn is due to the activation of signaling pathways leading to the increase in the pool and catalytic activities of rubisco and other Calvin cycle enzymes.

Ethylene is involved in the regulation of many growth and developmental processes in plants. Signaling pathways of the hormone are activated by five receptors, which are localized in membranes of endoplasmic reticulum and are similar to bacterial two-component histidine kinases. In the air, ethylene receptors activate CTR1 protein, which is a negative regulator (repressor) of nuclear protein--EIN2. In turn, EIN2 is an activator of transcriptional factors cascade responsible for the regulation of the expression of ethylene response genes. The level of EIN3, as well as other elements of ethylene signal transduction pathway, is subjected to complicated regulations on transcriptional and posttranslational levels, in which other internal and environmental factors are involved.

Transitory starch is accumulated during the day and is the main source of energy for the cell metabolism during the night. The observed periodical starch degradation has become a model often used by scientist in their experiments. Starch granule degradation could be divided into 2 periods: initiation of degradation and digestion of amylopectin and amylose into maltooligosaccharide and their derivative. Key meaning is attributed in this process to beta-amylaze, product of its activity beta-maltose is transported to the cytosole and there it subjects farthest conversions. It has been demonstrated that a number of enzymes take part in the starch degradation process. However, the way of regulating their activity is still not fully explained. There is most important elements effecting rate of starch decomposition: day cycle, starch phosphorylation and regulation of enzyme activity. It proceeds through redox potential, pH changes and phosphorylation of protein involved in starch degradation due specific phosphatases. The purpose of the current work is to systematize the knowledge of the Arabidopsis thaliana L. leaf starch degradation. The results of the recent research cast a new light on the starch degradation process as well as on its control.

ATP binding cassette (ABC) transporters, which are found in all species, are known mainly for their ability to confer drug resistance. They have been thoroughly studied in mammals, where they became the center of interest for clinical reasons related to the resistance of tumor cells to chemotherapy treatment. Less is known about plant members of the ABC family, however, growing number of reports on their role in different physiological processes attract attention. The vacuolar ABC transporters in plants characterized to date are involved in the intracellular sequestration of cytotoxins (e.g. herbicides), as well as the products of endogenous metabolism like chlorophyll catabolites. Others localized within plasma membrane are active in the transport of secondary metabolites or phytohormones. Finally certain transporters are present in cell organelles and play a role in such processes as P oxidation. Here, we briefly introduce these proteins, and describe structural characteristic and physiological aspect of their activity in a plant cell.