Search Results (21)

Apera spica-venti is a weed that is threatening agricultural crops worldwide. Current reports do not fully agree on the biology of the weed, regarding the viability of diaspores, nor is there sufficient information on how different factors affect the germination of its seeds, such as the abundance of soil where the mother plant (plants from which diaspores (caryopsis) were collected) has grown or the effect of biostimulants on their germination. Therefore, the main aim of this study was to compare the germination of newly harvested seeds of A. spica-venti (3 months after harvest) with seeds that had been stored for 1, 2, 3, 4, or 5 years. Furthermore, the influence of seed age, weed location, and biostimulants (silicon and algal liquids) on the germination of A. spica-venti diaspores was checked. Three-year-old seeds showed the highest percentage of germination, and their germination process was positively correlated with soil abundance (from sites of mother plant material collection) and macronutrients (N, P, K). The strongest correlations were recorded for 3- and 4-year-old seeds. A. spica-venti seeds treated with biostimulant preparations were characterized by varying percentages of germination. No clear trend was noted regarding the germination capacity of the harvested seeds as the diaspores aged, and it depended on the type of stimulant and the place of origin of the seed. Moreover, seeds from the harvest year treated with the stimulant were characterized by a higher germination percentage. A. spica-venti is a highly fecund weed, a trait that makes it very common in crops, appearing en masse and providing formidable competition to crops, thus causing significant yield losses. Awareness of the vitality of diaspores will allow for the possible regulation and control of this weed in order to prevent yield loss in crops. The theme of diaspore viability warrants further investigation. Further research should include observations of factors affecting germination, including new stimulants emerging on the agricultural market. Full article

The information on the involvement of hormones in the release of dormancy in grass caryopses is still insufficient. The main aim of the present study was to deepen our understanding of the mechanism dormancy release in Avena fatua L. caryopses by after-ripening in relation to abscisic acid (ABA) and gibberellins (GAs). The after-ripening of florets during dry storage resulted in dormancy removal in caryopses, allowing their germination at 20 to 30 °C. Sensitivity to ABA and paclobutrazol (PAC), a GAs biosynthesis inhibitor, decreased as the after-ripening period was extended. After-ripening increased the ABA content in the embryos of dry caryopses and decreased the total content of bioactive GAs, except for GA₁, the content of which increased. Accordingly, the ABA/GAs ratio was increased, and the ABA/GA₁ ratio was lowered due to after-ripening. After-ripening led to a decrease in the ABA content and increased the bioactive GAs contents, including GA₁ and GA₆, regarded as the most important for germination, in the embryos within 18 h of caryopses germination. The results obtained indicate that the embryos of dormant caryopses contained sufficient levels of bioactive GA₁ and GA₆ at early stages of germination, but their germination was prevented due to having too high an ABA concentration. It seems that the agents most important in dormancy removal through after-ripening include a reduction in the ABA content and sensitivity, as well as an increase in the bioactive GAs, particularly GA₁ and GA₆, in the embryos of germinating caryopses, which brings about a reduction in the ABA/GAs, ABA/GA₁, and ABA/GA₆ ratios, thus enabling germination. Full article

Plant A/T-rich sequence- and zinc-binding protein (PLATZ) is a type of plant-specific zinc-dependent DNA-binding protein that binds to A/T-rich DNA sequences. This family is essential for plant growth, development, and stress response. In this study, 15 OsPLATZs were identified in the rice genome with complete PLATZ-conserved domains by CD-search, similar to those found in angiosperms. Multi-species phylogenetic analysis showed that PLATZs were conserved in photosynthetic organisms, and an evolutionary branch unique to angiosperms was identified among members of the PLATZ family. Fifteen OsPLATZs were represented by five groups, each with distinct characteristics. An analysis of protein structures and sequence motifs showed that OsPLATZs were similar within groups, but varied between them. The expression profile and qRT-PCR results showed that OsPLATZs had distinct expression patterns in different tissues, with some responding to stress induction. Most of the OsPLATZs localized to the nuclei, and were predicted to bind to DNA sequences by AlphaFold3, suggesting that they likely function as conventional transcription factors. We also identified OsPLATZ1, a caryopsis-specific gene that regulates grain filling and caryopsis development in rice. This research lays the foundation for exploring the structural diversity, evolutionary traits, expression profile, and possible roles of PLATZ transcription factors in rice. Full article

High temperature impairs starch biosynthesis in developing rice grains and thereby increases chalkiness, affecting the grain quality. Genome encoded microRNAs (miRNAs) fine-tune target transcript abundances in a spatio-temporal specific manner, and this mode of gene regulation is critical for a myriad of developmental processes as well as stress responses. However, the role of miRNAs in maintaining rice grain quality/chalkiness during high daytime temperature (HDT) stress is relatively unknown. To uncover the role of miRNAs in this process, we used five contrasting rice genotypes (low chalky lines Cyp, Ben, and KB and high chalky lines LaGrue and NB) and compared the miRNA profiles in the R6 stage caryopsis samples from plants subjected to prolonged HDT (from the onset of fertilization through R6 stage of caryopsis development). Our small RNA analysis has identified approximately 744 miRNAs that can be grouped into 291 families. Of these, 186 miRNAs belonging to 103 families are differentially regulated under HDT. Only two miRNAs, Osa-miR444f and Osa-miR1866-5p, were upregulated in all genotypes, implying that the regulations greatly varied between the genotypes. Furthermore, not even a single miRNA was commonly up/down regulated specifically in the three tolerant genotypes. However, three miRNAs (Osa-miR1866-3p, Osa-miR5150-3p and canH-miR9774a,b-3p) were commonly upregulated and onemiRNA (Osa-miR393b-5p) was commonly downregulated specifically in the sensitive genotypes (LaGrue and NB). These observations suggest that few similarities exist within the low chalky or high chalky genotypes, possibly due to high genetic variation. Among the five genotypes used, Cypress and LaGrue are genetically closely related, but exhibit contrasting chalkiness under HDT, and thus, a comparison between them is most relevant. This comparison revealed a general tendency for Cypress to display miRNA regulations that could decrease chalkiness under HDT compared with LaGrue. This study suggests that miRNAs could play an important role in maintaining grain quality in HDT-stressed rice. Full article

The study of the genetic control of maize seed development and seed-related pathways has been one of the most important themes approached by the Italian scientific community. Maize has always attracted the interest of the Italian community of agricultural genetics since its beginning, as some of its founders based their research projects on and developed their “schools” by adopting maize as a reference species. Some of them spent periods in the United States, where maize was already becoming a model system, to receive their training. In this manuscript we illustrate the research work carried out in Italy by different groups that studied maize kernels and underline their contributions in elucidating fundamental aspects of caryopsis development through the characterization of maize mutants. Since the 1980s, most of the research projects aimed at the comprehension of the genetic control of seed development and the regulation of storage products’ biosyntheses and accumulation, and have been based on forward genetics approaches. We also document that for some decades, Italian groups, mainly based in Northern Italy, have contributed to improve the knowledge of maize genomics, and were both fundamental for further international studies focused on the correct differentiation and patterning of maize kernel compartments and strongly contributed to recent advances in maize research. Full article

Cereal caryopses are rich in 5-n-alk(en)ylresorcinols, antimicrobial compounds. In this paper, the correlation between the presence of resorcinolic lipids on the surface of cereal grains and the susceptibility of their seedlings to infection by Rhizoctonia solani or Fusarium culmorum was evaluated. The declines in length of both the roots and coleoptiles were observed in barley seedlings of Scarlett and Rabel cultivars grown from the wax-impoverished seeds infected with F92 and F93 strains of Rhizoctonia solani, respectively. Regarding wheat, R. solani F93 significantly reduced only the coleoptile growth. Resorcinolic lipids, being the mixture of homologues with C17–C25 carbon chains, were the only compounds washed off wheat caryopses by chloroform. Moreover, the better anti-Rhizoctonia solani F93 activity of 5-n-alk(en)ylresorcinols of wheat grains than that of rye caryopsis lipids was proven by the poisoned medium technique. Two saturated homologues (C21:0 and C23:0) were the most effective inhibitors of the mycelial growth of this fungus. Thus, the susceptibilities of barley and wheat seedlings to some fungal pathogens have been found to be related to the content and composition of 5-n-alk(en)ylresorcinols in the waxy layer of cereal grains, confirming the protective role of these compounds, during the early stages of cereal development. Full article

Wheat germ (WG)’s shelf life after the milling process is incredibly short because of the presence of enzymes that aggravate the oxidation process; thus, stabilization is required in order to exploit the nutrients and bioactive compounds within WG. The critical point for the oxidation process is the mechanical treatment used to separate WG from the kernel, which exposes the lipid fraction to the air. Showing the connection between the quality of durum wheat, considering its storage management, and wheat germ oil (WGO), extracted with a cold press, solvent and supercritical CO₂, is the aim of the study. The acidity and peroxide values were analyzed to evaluate lipid oxidation, while fatty acids, tocols, sterols and policosanols were evaluated for WGO characterization. The first fundamental step to control lipid oxidation is raw material management. Subsequently, the tempering phase of durum wheat, which is applied before the degermination process, is the most critical point for oxidation to develop because of the increase in moisture in the caryopsis and the activation of lipase and lipoxygenase. This represents a paradox: in order to stabilize the germ with degermination, first it seems inevitable to carry out a process that destabilizes it. To retains its highest quality, this will lead to a better use of the whole grain by reducing WG and by-product waste. Full article

The seed is the fundamental unit of the dispersal of dry, dehiscent fruits, in which the fruit splits open at maturity to allow for seed dispersal. However, dry fruits may be indehiscent and therefore represent the dispersal unit (DU). Cereals possess a one-seeded fruit, whereby the seed coat and the fruit coat are fused together to generate the caryopsis. This caryopsis may be covered by floral bracts to generate two types of DUs, namely florets, whereby the caryopsis is enclosed by the lemma and the palea (e.g., Avenasterilis) or spikelet, whereby the floret(s) is further covered by the glumes (Triticum turgidum var. dicoccoides). Here, we highlight the dead coverings enclosing the caryopsis in cereals, namely the husks as an integral component of the dispersal unit that play multifaceted roles in grain biology. Thus, besides protection and dispersal means, the husks function as a rich maternal supply of proteins and metabolites for enhancing growth and development, combat potential pathogens as well as confer tolerance to abiotic stresses. These attributes might have broad implications for crop performance, plant population dynamics and diversity in ecological systems, and for conservation of genetic resources in seed banks. Full article

Durum wheat is a staple crop for the Mediterranean diet because of its adaptability to environmental pressure and for its large use in cereal-based food products, such as pasta and bread, as a source of calories and proteins. Durum wheat whole grains are also highly valued for their peculiar amount of dietary fiber and minerals, as well as bioactive compounds of particular interest for their putative health-beneficial properties, including polyphenols, carotenoids, tocopherols, tocotrienols, and phytosterols. In Mediterranean environments, durum wheat is mostly grown under rainfed conditions, where the crop often experiences environmental stresses, especially water deficit and soil salinity that may induce a hyperosmotic stress. In particular, changes in C and N accumulation due to these abiotic conditions, during grain filling, can influence starch and storage protein amount and composition in durum wheat caryopsis, thus influencing yield and quality traits. Recent advancements regarding the influence of water deficit and salinity stress on durum wheat are critically discussed. In particular, a focus on stress-induced changes in (a) grain protein content and composition in relation to technological and health quality; (b) starch and dietary fiber accumulation and composition; (c) phytochemical composition; (d) health-related grain micronutrient accumulation, such as Fe and Zn. Full article

The integumentary tissues of plant seeds protect the embryo (new sporophyte) forming in them from unfavorable external conditions; therefore, comprehensive knowledge about the structural and functional specificity of seed covers in various plants may be of both theoretical and practical interest. As a result of our study, additional data were obtained on the morphological and ultrastructural features of the formation of a multilayer skin of wheat (Triticum aestivum L.) kernel (caryopsis). The ultrastructure research analysis showed that differentiation of the pericarp and inner integument of the ovule leads to the formation of functionally different layers of the skin of mature wheat grain. Thus, the differentiation of exocarp and endocarp cells is accompanied by a significant thickening of the cell walls, which reliably protect the ovule from adverse external conditions. The cells of the two-layer inner integument of the ovule differentiate into cuticular and phenolic layers, which are critical for protecting daughter tissues from various pathogens. The epidermis of the nucellus turns into a layer of mucilage, which apparently helps to maintain the water balance of the seed. Morphological and ultrastructural data showed that the formation of the kernel’s skin occurs in coordination with the development of the embryo and endosperm up to the full maturity of the kernel. This is evidenced by the structure of the cytoplasm and nucleus, characteristic of metabolically active protoplasts of cells, which is observed in most integumentary layers at the late stages of maturation. This activity can also be confirmed by a significant increase in the thickness of the cell walls in the cells of two layers of the exocarp and in cross cells in comparison with the earlier stages. Based on these results, we came to the conclusion that the cells of a majority in the covering tissues of the wheat kernel during its ontogenesis are transformed into specialized layers of the skin by terminal differentiation. Full article

In meadow fescue (Festuca pratensis Huds.), a perennial fodder grass plant characterized by high quality and yield potential, seed shattering makes seed production difficult. The objective of the research was to compare two subpopulations, differing in a tendency to seed shattering, with respect to their variability in the beginning of the heading and flowering stages, their morphological traits (plant height and panicle length), and changes occurring at the site of the bonding between the caryopsis and the pedicel. The subpopulations were obtained by divergent selection carried out on four meadow fescue cultivars. Significant variability in years and subpopulations in respect of the tested traits was found. The subpopulation with a low tendency to seed shattering was characterized by a 2–3 day delay in the beginning of the heading and flowering stages. However, in both the subpopulations, a good flowering stage synchronization was found, with its variability being several times smaller when compared with the heading stage. Between the starting dates of these stages, a significant correlation was found (r = 0.828; p < 0.01). The clones with a high tendency of seed shattering were approximately 7 cm shorter, while the length of panicles was similar in both the subpopulations. The analysis, which was performed with the use of a scanning microscope, showed that, in genotypes with a low tendency to shattering, the formation of the abscission layer was four days late, which may confirm the effectiveness of the carried out selection. Full article

Anthocyanin is a flavonoid compound with potential antioxidant properties beneficial to human health and sustains plant growth and development under different environmental stresses. In black rice, anthocyanin can be found in the stems, leaves, stigmas, and caryopsis. Although the anthocyanin biosynthesis in rice has been extensively studied, limited knowledge underlying the storage mechanism and transporters is available. This study undertook the complementation of computational and transcriptome analysis to decipher a potential multidrug and toxic compound extrusion (MATE) gene candidate for anthocyanin transportation in black rice caryopsis. The phylogenetic analysis showed that OsMATE34 has the same evolutionary history and high similarities with VvAM1, VvAM3, MtMATE2, SlMATE/MTP77, RsMATE8, AtFFT, and AtTT12 involved in anthocyanin transportation. RNA sequencing analysis in black caryopsis (Bc; Bc11, Bc18, Bc25) and white caryopsis (Wc; Wc11, Wc18, Wc25), respectively, at 11 days after flowering (DAF), 18 DAF, and 25 DAF revealed a total of 36,079 expressed genes, including 33,157 known genes and 2922 new genes. The differentially expressed genes (DEGs) showed 15,573 genes commonly expressed, with 1804 and 1412 genes uniquely expressed in Bc and Wc, respectively. Pairwise comparisons showed 821 uniquely expressed genes out of 15,272 DEGs for Wc11 vs. Bc11, 201 uniquely expressed genes out of 16,240 DEGs for Wc18 vs. Bc18, and 2263 uniquely expressed genes out of 16,240 DEGs for Wc25 vs. Bc25. Along with anthocyanin biosynthesis genes (OsPAL, OsCHS, OsCHI, OsF3H, OsDFR, OsANS, and OsUFGT/Os3GT), OsMATE34 expression was significantly upregulated in all Bc but not in Wc. OsMATE34 expression was similar to OsGSTU34, a transporter of anthocyanin in rice leaves. Taken together, our results highlighted OsMATE34 (Os08g0562800) as a candidate anthocyanin transporter in rice caryopsis. This study provides a new finding and a clue to enhance the accumulation of anthocyanin in rice caryopsis. Full article

Anthocyanins belong to the group of flavonoid compounds broadly distributed in plant species responsible for attractive colors. In black rice (Oryza sativa L.), they are present in the stems, leaves, stigmas, and caryopsis. However, there is still no scientific evidence supporting the existence of compartmentalization and trafficking of anthocyanin inside the cells. In the current study, we took advantage of autofluorescence with anthocyanin’s unique excitation/emission properties to elucidate the subcellular localization of anthocyanin and report on the in planta characterization of anthocyanin prevacuolar vesicles (APV) and anthocyanic vacuolar inclusion (AVI) structure. Protoplasts were isolated from the stigma of black and brown rice and imaging using a confocal microscope. Our result showed the fluorescence displaying magenta color in purple stigma and no fluorescence in white stigma when excitation was provided by a helium–neon 552 nm and emission long pass 610–670 nm laser. The fluorescence was distributed throughout the cell, mainly in the central vacuole. Fluorescent images revealed two pools of anthocyanin inside the cells. The diffuse pools were largely found inside the vacuole lumen, while the body structures could be observed mostly inside the cytoplasm (APV) and slightly inside the vacuole (AVI) with different shapes, sizes, and color intensity. Based on their sizes, AVI could be grouped into small (Ф < 0.5 um), middle (Ф between 0.5 and 1 um), and large size (Ф > 1 um). Together, these results provided evidence about the sequestration and trafficking of anthocyanin from the cytoplasm to the central vacuole and the existence of different transport mechanisms of anthocyanin. Our results suggest that stigma cells are an excellent system for in vivo studying of anthocyanin in rice and provide a good foundation for understanding anthocyanin metabolism in plants, sequestration, and trafficking in black rice. Full article

Anthocyanins are antioxidants used as natural colorants and are beneficial to human health. Anthocyanins contribute to reactive oxygen species detoxification and sustain plant growth and development under different environmental stresses. They are phenolic compounds that are broadly distributed in nature and are responsible for a wide range of attractive coloration in many plant organs. Anthocyanins are found in various parts of plants such as flowers, leaves, stems, shoots, and grains. Considering their nutritional and health attributes, anthocyanin-enriched rice or pigmented rice cultivars are a possible alternative to reduce malnutrition around the globe. Anthocyanin biosynthesis and storage in rice are complex processes in which several structural and regulatory genes are involved. In recent years, significant progress has been achieved in the molecular and genetic mechanism of anthocyanins, and their synthesis is of great interest to researchers and the scientific community. However, limited studies have reported anthocyanin synthesis, transportation, and environmental conditions that can hinder anthocyanin production in rice. Rice is a staple food around the globe, and further research on anthocyanin in rice warrants more attention. In this review, metabolic and pre-biotic activities, the underlying transportation, and storage mechanisms of anthocyanins in rice are discussed in detail. This review provides potential information for the food industry and clues for rice breeding and genetic engineering of rice. Full article

Dry fruits consist of two types, dehiscent and indehiscent, whereby the fruit is splitting open or remains closed at maturity, respectively. The seed, the dispersal unit (DU) of dehiscent fruits, is composed of three major parts, the embryo and the food reserve, encapsulated by the maternally-derived organ, the seed coat. Indehiscent fruit constitutes the DU in which the embryo is covered by two protective layers (PLs), the seed coat and the fruit coat. In grasses, the caryopsis, a one-seeded fruit, can be further enclosed by the floral bracts to generate two types of DUs, florets and spikelets. All protective layers enclosing the embryo undergo programmed cell death (PCD) at maturation and are thought to provide mainly a physical shield for embryo protection and a means for dispersal. In this review article, I wish to highlight the elaborate function of these dead organs enclosing the embryo as unique storage structures for beneficial substances and discuss their potential role in seed biology and ecology. Full article