Pollen-Pistil Interaction

The aim of this Special Issue is to highlight the molecular dialogue between the pollen tube and the pistil. This is achieved with original articles and reviews which show how this dialogue is controlled at the genomic and molecular levels. During the angiosperm’s double fertilization, the pollen tube must enter female tissues, bypass numerous physical barriers to reach the micropyle, and release gametes to complete the fertilization process with the final fusion between male and female gametes. There are molecular signals produced by the pistil that are intercepted by the receptors located primarily at the tip of the tube, which generate effects that modulate its growth activity; in turn, the pollen tube releases molecules that determine effects on the pistil cells. Thus, a complex dialogue develops between the female and male counterparts, whose language is made up of an expansive molecular alphabet that includes proteins, glycoproteins, arabinogalactan-proteins, lipid-binding proteins, nanovesicles, ions, amino acids, sugars, hormones, reactive oxygen species (ROS), and modulators of gene expression

Pollen-Pistil Interaction

The aim of this Special Issue is to highlight the molecular dialogue between the pollen tube and the pistil. This is achieved with original articles and reviews which show how this dialogue is controlled at the genomic and molecular levels. During the angiosperm’s double fertilization, the pollen tube must enter female tissues, bypass numerous physical barriers to reach the micropyle, and release gametes to complete the fertilization process with the final fusion between male and female gametes. There are molecular signals produced by the pistil that are intercepted by the receptors located primarily at the tip of the tube, which generate effects that modulate its growth activity; in turn, the pollen tube releases molecules that determine effects on the pistil cells. Thus, a complex dialogue develops between the female and male counterparts, whose language is made up of an expansive molecular alphabet that includes proteins, glycoproteins, arabinogalactan-proteins, lipid-binding proteins, nanovesicles, ions, amino acids, sugars, hormones, reactive oxygen species (ROS), and modulators of gene expression

Allergenic risk assessment of urban parks: Towards a standard index.

Allergenicity indices are a powerful tool to assess the health hazard posed by urban parks to pollen allergic subjects. Nonetheless, only few indices have been developed and applied to urban vegetation in the last decade, and they were never compared nor standardised over the same dataset. To address this issue, in this paper the two best-known allergenicity indices, the Urban Green Zones Allergenicity Index (IUGZA) and the Specific Allergenicity Index (SAI), have been calculated for the same park (the Botanical Garden of Bologna), collecting vegetation data through both systematic sampling and arboreal census. The results obtained with the two data collection methods were comparable for both indices, indicating systematic sampling as a reliable approximation of the total census. Besides, the allergenic risk resulted moderate to high according to SAI, and very low according to IUGZA. Since SAI does not consider the total volume of the vegetation, it was deemed less reliable than IUGZA in evaluating the allergenicity of an enclosed green space

Editorial: Regulation of pollen tube growth, volume II

The pollen tube is an extension produced by the pollen grain when conditions are favorable; thus, the pollen tube is important in seed plant reproduction because it transports male gametes. However, it is also an excellent system for studying various plant cell processes that are common to sink organs or tissues (Kroeger and Geitmann, 2012). The pollen tube has been used to study a variety of processes, including vesicular transport, cytoskeletal organization, cell wall deposition, ion gradients, intracellular signaling. Since the pollen tube grows by contacting and signaling to pistil cells, it is also a model for studying cell-cell communication (Broz and Bedinger, 2021). Moreover, the pollen tube is involved in self-incompatibility (SI) processes that regulate reproduction and thus promote hybridization and genetic variability (Mandrone et al., 2019). SI is regulated by several factors, and in some cases, such as citrus, it is an important tool for producing seedless mandarins (Gentile et al., 2012). Pollen tube and pollen can also be targets of environmental stresses (Ledesma and Sugiyama, 2019), which can impair plant reproductive success, resulting in lower productivity of agronomically important plants and increasing allergenicity (pollinosis) (Armentia et al., 2019; Singh and Mathur, 2021)

BFKL at Next-to-Next-to-Leading Order

We determine an approximate expression for the O(alpha_s^3) contribution chi_2 to the kernel of the BFKL equation, which includes all collinear and anticollinear singular contributions. This is derived using recent results on the relation between the GLAP and BFKL kernels (including running-coupling effects to all orders) and on small-x factorization schemes. We present the result in various schemes, relevant both for applications to the BFKL equation and to small-x evolution of parton distributions.Comment: 34 pages, 6 figures, TeX with harvmac. Various small typos corrects, in particular first term in eq D.3. Final version to be published in Nucl. Phys.

Cytoskeleton, Transglutaminase and Gametophytic Self-Incompatibility in the Malinae (Rosaceae)

Self-incompatibility (SI) is a complex process, one out of several mechanisms that prevent plants from self-fertilizing to maintain and increase the genetic variability. This process leads to the rejection of the male gametophyte and requires the co-participation of numerous molecules. Plants have evolved two distinct SI systems, the sporophytic (SSI) and the gametophytic (GSI) systems. The two SI systems are markedly characterized by different genes and proteins and each single system can also be divided into distinct subgroups; whatever the mechanism, the purpose is the same, i.e., to prevent self-fertilization. In Malinae, a subtribe in the Rosaceae family, i.e., Pyrus communis and Malus domestica, the GSI requires the production of female determinants, known as S-RNases, which penetrate the pollen tube to interact with the male determinants. Beyond this, the penetration of S-RNase into the pollen tube triggers a series of responses involving membrane proteins, such as phospholipases, intracellular variations of cytoplasmic Ca2+, production of reactive oxygen species (ROS) and altered enzymatic activities, such as that of transglutaminase (TGase). TGases are widespread enzymes that catalyze the post-translational conjugation of polyamines (PAs) to different protein targets and/or the cross-linking of substrate proteins leading to the formation of cross-linked products with high molecular mass. When actin and tubulin are the substrates, this destabilizes the cytoskeleton and inhibits the pollen-tube's growth process. In this review, we will summarize the current knowledge of the relationship between S-RNase penetration, TGase activity and cytoskeleton function during GSI in the Malinae

Perturbatively Stable Resummed Small x Evolution Kernels

We present a small x resummation for the GLAP anomalous dimension and its corresponding dual BFKL kernel, which includes all the available perturbative information and nonperturbative constraints. Specifically, it includes all the information coming from next-to-leading order GLAP anomalous dimensions and BFKL kernels, from the constraints of momentum conservation, from renormalization-group improvement of the running coupling and from gluon interchange symmetry. The ensuing evolution kernel has a uniformly stable perturbative expansion. It is very close to the unresummed NLO GLAP kernel in most of the HERA kinematic region, the small x BFKL behaviour being softened by momentum conservation and the running of the coupling. Next-to-leading corrections are small thanks to the constraint of gluon interchange symmetry. This result subsumes all previous resummations in that it combines optimally all the information contained in them.Comment: 44 pages, 12 figures, plain TeX with harvmac. Final version, to be published in Nucl. Phys. B. Discussion of integrated vs. unintegrated pdfs added, see eqns. 5.5-5.7, 6.26-6.29. Figures 6-12 update

New bread formulation with improved rheological properties and longer shelf-life by the combined use of transglutaminase and sourdough

The combined use of the protein reticulating enzyme transglutaminase (TGase) and a selected microbial consortium of Lactobacillus sanfranciscensis and Candida milleri for improving the rheological properties, aroma, and shelf-life of a bakery product was evaluated. A microbial TGase, showing the highest activity over a wide temperature range on different protein substrates, was selected among different types. Results showed that this TGase was able to produce isodipeptide bonds, especially in the gluten fraction, leading to the formation of protein aggregates, which improved the structure of a sourdough bakery product. The microbial TGase in combination with sourdough exhibited a positive synergistic effect allowing the production of flavor-enriched bread, with rheological properties similar to those of standard bread

Finite-top-mass effects in NNLO Higgs production

We construct an accurate approximation to the exact NNLO cross section for Higgs production in gluon-gluon fusion by matching the dominant finite top mass corrections recently computed by us to the known result in the infinite mass limit. The ensuing corrections to the partonic cross section are very large when the center of mass energy of the partonic collision is much larger than the Higgs mass, but lead to a moderate correction at the percent level to the total Higgs production cross section at the LHC. Our computation thus reduces the uncertainty related to these corrections at the LHC from the percent to the per mille level.Comment: 4 pages, 4 figures; to be published in the proceedings of QCD2008. Reference adde

Resummation of Singlet Parton Evolution at Small x

We propose an improvement of the splitting functions at small x which overcomes the apparent problems encountered by the BFKL approach. We obtain a stable expansion for the x-evolution function chi(M) near M=0 by including in it a sequence of terms derived from the one- and two-loop anomalous dimension gamma. The requirement of momentum conservation is always satisfied. The residual ambiguity on the splitting functions is effectively parameterized in terms of the value of lambda, which fixes the small x asymptotic behaviour x^-lambda of the singlet parton distributions. We derive from this improved evolution function an expansion of the splitting function which leads to good apparent convergence, and to a description of scaling violations valid both at large and small x.Comment: 16 pages, 6 figures, LaTeX with epsfig; final version, to be published in Nucl. Phys. B. A few typos corrected for the recor