The need for the vernalization duration of soft winter wheat collection samples

The need for vernalization is a duration-dependent effect of low, positive temperatures in order to ensure the plants' transition to generative development. If the requirement for the duration of germination is not met, the plant will not enter the stage of forming generative organs. The vernalization requirements of winter soft wheat samples of different geographical origins are determined. An assessment of the vernalization period duration influence on the severity of the elements of the yield structure is given. The research material consisted of 15 cultivars of soft winter wheat of various geographic origin. The samples were germinated in paper rolls, then vernalized in a climatic chamber at a temperature of 3–5 ºС for 60, 50, and 40 days. At the end of vernalization, 10 plants of each sample were planted in a greenhouse. The dates of the onset of phenological phases were noted: tube emergence, earing, flowering. To determine the main elements of the yield structure, a structural analysis of plants was carried out. With an increase in the vernalization period, a decrease in the interfacial periods from tube emergence to flowering was noted. The influence of the timing of vernalization was noted on the manifestation of the spike length trait. It was found that the total number of stems and the number of productive stems in almost all varieties decreases with an increase in the period of vernalization. Significant differences between collection varieties in the need for vernalization, due to both their geographical origin and the genotype of plants are revealed. In all the studied forms, with an increase in the period of vernalization, the rate of plant development increased to varying degrees, the total number of stems, the productive stem and the length of the spike decreased.

Application of photometry for diagnostics of nitrogen nutrition in spring barley

The article discusses a method for diagnosing nitrogen nutrition of spring barley (Hordeum vulgare L.) in different phases of the growing season using a photometric device (N-tester) Yara. The studies were carried out in the conditions of the Moscow region (Russia) on the Mikhailovsky spring barley variety on sod-podzolic medium loamy soils with a high and medium content of phosphorus and potassium and a low content of humus (1.9). The agrometeorological conditions of the growing season of spring barley were characterized by sharp fluctuations in air temperature and the amount of precipitation over decades of the month and in comparison with average long-term observations. Abundant and prolonged precipitation during the grain ripening phase led to lodging in most of the experiments, which affected the yield. To diagnose crops, a model experiment was laid with the introduction of increasing doses of nitrogen fertilizers into pre-sowing cultivation with a step of 30, at which the dose of nitrogen ranged from 30 to 150 kg/ha. Diagnostics was carried out in three phases of vegetation: tube emergence ((Z42), earing (Z55), milk ripeness of grain (Z73) with the Yara N-tester and with the help of stem diagnostics according to the modified method of V. Zerling. The results of photometric diagnostics in the stemming phase (Z42) have a strong correlation with the yield of spring barley grain and with the results of stem diagnostics (R = 0.85). Wherein, the N-tester readings in the earing phase (Z55) and milk ripeness of grain (Z73) with yield R = 0.23 and R = 0.17, respectively, have a weak correlation. This is possibly due to lodging of crops and a change in yield, not as a result of poor plant nutrition, but with difficult mechanized harvesting.

Overexpression of the Aspergillus fumigatus Small GTPase, RsrA, Promotes Polarity Establishment during Germination

Cell polarization comprises highly controlled processes and occurs in most eukaryotic organisms. In yeast, the processes of budding, mating and filamentation require coordinated mechanisms leading to polarized growth. Filamentous fungi, such as Aspergillus fumigatus, are an extreme example of cell polarization, essential for both vegetative and pathogenic growth. A major regulator of polarized growth in yeast is the small GTPase Rsr1, which is essential for bud-site selection. Here, we show that deletion of the putative A. fumigatus ortholog, rsrA, causes only a modest reduction of growth rate and delay in germ tube emergence. In contrast, overexpression of rsrA results in a morphogenesis defect, characterized by a significant delay in polarity establishment followed by the establishment of multiple growth axes. This aberrant phenotype is reversed when rsrA expression levels are decreased, suggesting that correct regulation of RsrA activity is crucial for accurate patterning of polarity establishment. Despite this finding, deletion or overexpression of rsrA resulted in no changes of A. fumigatus virulence attributes in a mouse model of invasive aspergillosis. Additional mutational analyses revealed that RsrA cooperates genetically with the small GTPase, RasA, to support A. fumigatus viability.

Volatile self-inhibitor of spore germination in pathogenic Mucorale Rhizopus arrhizus

ABSTRACT Rhizopus arrhizus is a common pathogenic Mucoralean mold that exists as a saprophyte, and is disseminated through sporangiospores, which germinate to form mycelia under suitable environmental or infection settings. Such morphological transitions are often mediated by self-produced effector molecules in a density-dependent fashion. This study aimed to elucidate if a quorum-dependent, cell-density-driven phenomenon exists in R. arrhizus, and identify the molecule(s) involved. The germination of R. arrhizus was observed to be reliant on the seeding density, with nearly 71% and 47% germination in Sabouraud dextrose and glucose asparagine media respectively at 1 × 105–1 × 106 spores/mL, and only 10% and 1% germination respectively with 1 × 108 spores/mL. The late-growth-stage supernatant also hindered the spore germination and liquid-culture biomass in a dose-dependent way. These effects were being mediated by a volatile inhibitor present in the headspace and supernatant of R. arrhizus cultures, identified as 2-methyl-2-butene by gas chromatography and electron ionization-quadrupole mass spectrometry. The compound was present in a density-dependent manner and considerably impaired fungal germ-tube emergence and elongation during germination. Spore swelling remained unaffected. Multiple thin protrusions comprising of F-actin and microtubules were seen emanating from the treated cells, suggestive of filopodia-like and cytoneme-like extensions. The same compound was also detected in Rhizomucor pusillus.

Cysteine-rich peptides promote interspecific genetic isolation in Arabidopsis

Reproductive isolation is a prerequisite for speciation. Failure of communication between female tissues of the pistil and paternal pollen tubes imposes hybridization barriers in flowering plants. Arabidopsis thaliana LURE1 (AtLURE1) peptides and their male receptor PRK6 aid attraction of the growing pollen tube to the ovule. Here, we report that the knockout of the entire AtLURE1 gene family did not affect fertility, indicating that AtLURE1-PRK6–mediated signaling is not required for successful fertilization within one Arabidopsis species. AtLURE1s instead function as pollen tube emergence accelerators that favor conspecific pollen over pollen from other species and thus promote reproductive isolation. We also identified maternal peptides XIUQIU1 to -4, which attract pollen tubes regardless of species. Cooperation between ovule attraction and pollen tube growth acceleration favors conspecific fertilization and promotes reproductive isolation.

Peroxisomal Localization of CuZn Superoxide Dismutase in the Male Reproductive Tissues of the Olive Tree

Superoxide dismutases (SODs) are a class of antioxidant enzymes which catalyze the dismutation of superoxide into oxygen and hydrogen peroxide, therefore controlling cellular levels of Reactive Oxygen Species (ROS). In the mature pollen grains of the olive tree, the presence of several forms of CuZn-SOD and the cytosolic localization of the enzyme have been described. The present study was aimed to elucidate the adaptation of the oxidative metabolism to the changing conditions occurring during the course of olive pollen formation, hydration and pollen tube emergence and growth. We used a polyclonal antibody (raised against a KLH-linked synthetic peptide including a consensus sequence for CuZn-SODs in olive pollen) in immunocytochemical experiments carried out by Fluorescence (FM) and Transmission Electron Microcopy (TEM).

Protein Kinase A Regulatory Subunit Isoforms Regulate Growth and Differentiation in Mucor circinelloides: Essential Role of PKAR4

ABSTRACTThe protein kinase A (PKA) signaling pathway plays a role in regulating growth and differentiation in the dimorphic fungusMucor circinelloides. PKA holoenzyme is comprised of two catalytic (C) and two regulatory (R) subunits. InM. circinelloides, four genes encode the PKAR1, PKAR2, PKAR3, and PKAR4 isoforms of R subunits. We have constructed null mutants and demonstrate that each isoform has a different role in growth and differentiation. The most striking finding is thatpkaR4is an essential gene, because only heterokaryons were obtained in knockout experiments. Heterokaryons with low levels of wild-type nuclei showed an impediment in the emission of the germ tube, suggesting a pivotal role of this gene in germ tube emergence. The remaining null strains showed different alterations in germ tube emergence, sporulation, and volume of the mother cell. ThepkaR2null mutant showed an accelerated germ tube emission and was the only mutant that germinated under anaerobic conditions when glycine was used as a nitrogen source, suggesting thatpkaR2participates in germ tube emergence by repressing it. From the measurement of the mRNA and protein levels of each isoform in the wild-type and knockout strains, it can be concluded that the expression of each subunit has its own mechanism of differential regulation. The PKAR1 and PKAR2 isoforms are posttranslationally modified by ubiquitylation, suggesting another regulation point in the specificity of the signal transduction. The results indicate that each R isoform has a different role inM. circinelloidesphysiology, controlling the dimorphism and contributing to the specificity of cyclic AMP (cAMP)-PKA pathway.