History and Prospects for the Application of X-Ray Diffraction Analysis in Seed Breeding and Seed Study

Introduction. X-ray analysis has been applied for visualizing the internal structure of various objects for over 100 years. However, this method began to be used for assessing the quality of plant seeds only in the early 1980s. The main impediment was a lack of specialized instruments, particularly X-ray sources, that could provide informative images. Advancements in the field of microfocus radiography allowed significant results to be achieved, including the preparation of the National Standard GOST R 596032021 "Agricultural Seeds. Methods of digital radiography".Aim. An analytical review of Russian research studies in the field of X-ray diffraction analysis of plant seeds.Materials and methods. Key stages in the development of microfocus X-ray diffraction analysis of seeds and individual parts of plants for agricultural and other purposes are considered. The design of instruments, including digital ones, created for the implementation of the method are described.Results. In order to obtain informative X-ray diffraction images of plant seeds, which objects are generally characterized by small sizes and small density, the focal spot of the X-ray tube should not exceed several tens of microns under the voltage of not higher than several tens of kilovolts. As a system for visualizing a latent X-ray image, it is preferable to use image receivers based on a screen with a photostimulated phosphor or flat-panel solid-state X-ray detectors. These instruments have been successfully used to identify and describe the radiographic signs of a normal seed and nine main types of defects for 600 plant species.Conclusion. In comparison with the conventional contact radiography, microfocus radiography produces X-ray images of seeds with a projection magnification of the image up to several tens of times. Such images permit highly detailed visualization of the structure of seeds that differ slightly in density.

Pectin remodeling belongs to a homeostatic system and triggers transcriptomic and hormonal modulations

Pectins occur in primary cell walls and consist of multiblock co‐polymers among which homogalacturonan (HG) is the simplest and most abundant form. Methylesterification patterns of HG are tuned by pectin methylesterases (PMEs), the activities of which are controlled by specific inhibitors (PMEIs). By impacting cell wall mechanical properties, PME‐mediated regulation of HG methylesterification plays a major role in several developmental processes, including seed germination and dark-grown hypocotyl elongation. Arabidopsis PME36 is preferentially expressed during the late stage of seed development and, using the knock‐out mutant pme36-1, we show here that PME36 is required to implement the characteristic pattern of de-methylesterified pectin in the mature seed. Surprisingly, while this pattern is strongly impaired in pme36-1 mature seed, no phenotypical effect is observed in the mutant during seed germination and dark-grown hypocotyl elongation, suggesting the existence of a compensatory mechanism overcoming the defect in pectin de-methylesterification. By analyzing hormone contents and gene expression, a strong, dynamic, and long-lasting physiological disorder is revealed in the mutant. These results suggest the existence of complex connections between pectin remodeling, transcriptomic regulations and hormonal homeostasis, modulating several physiological parameters to ensure the maintenance of a normal seed-to-seedling developmental program in pme36-1. Considered for a long time as an end-point passive effector mainly involved in modification of cell wall mechanics, the role of pectin methylesterification needs to be reconsidered as a modulator acting upstream of diverse regulatory pathways involved in plant development.

THE EFFECT OF THE FLORAL APPLICATION OF GIBBERELLIC ACID ON UNPOLLINATED INFLORESCENCES OF THE DATE PALM CULTIVAR ASSIANE (Phoenix dactylifera L.): A CASE STUDY OF FIGUIG OASIS, MOROCCO

The objective of the present study was to evaluate the effect of Gibberellic Acid in mitigate the phenomenon of parthenocarpy and improve the fruit set in the date palm cultivar Assiane at Figuig Oasis in Morocco. For this, four different concentrations of Gibberellic Acid (GA3) viz., 5, 50, 100, and 200 ppm were applied on unpollinated inflorescences in two phases. The first dose of GA3 is applied at the time of spadices burst while the second one is applied after the seven days of the first one. The results obtained from the study showed that the application of gibberellic acid on unpollinated female inflorescences had a significant effect on the removal of parthenocarpy which resulting in the higher normal-looking fruits with normal seed and by promoting the maturity of parthenocarpic fruits. In the case of rate of thinning, the application of GA3 @ 5-100 ppm enhanced the flower drop, while the application at higher concentration i.e. 200 ppm promotes the retention and development of flowers. Further, the analysis of the ripe fruits sugars content by high performance liquid chromatography (HPLC) suggests that the application of GA3 did not have any significant effect on the sugar content and these treatments are not significantly different from the fruits of pollinated flowers.

SDG711 Is Involved in Rice Seed Development through Regulation of Starch Metabolism Gene Expression in Coordination with Other Histone Modifications

SDG711 is a histone H3K27me2/3 transmethylase in rice, a homolog of CLF in Arabidopsis, and plays key roles in regulating flowering time and panicle development. In this work, we investigated the role of SDG711 in rice seed development. Overexpression and downregulation of SDG711 lead to a decrease and increase in the expression level of genes related to starch accumulation, resulting in smaller seeds or even seed abortion. ChIP assay showed that SDG711-mediated H3K27me3 changed significantly in genes related to endosperm development, and SDG711 can directly bind to the gene body region of several starch synthesis genes and amylase genes. In addition, H3K4me3 and H3K9ac modifications also cooperate with H3K27me3 to regulate the development of the endosperm. Our results suggest that the crosstalk between SDG711-mediated H3K27me3 and H3K4me3, and H3K9ac are involved in starch accumulation to control normal seed development.

Protection of Eggplant Seed Germination from the Inhibitory Effect of o-Cresol by Bioaugmentation of Soil with Pseudomonas monteilii Strain

Bulk production and widespread end use of cresol isomers in various industrial processes result in their ubiquitous presence in the environment. Cresols are highly toxic to both fauna and flora and are included in the list of priority pollutants. This study presents the effect of o-cresol on germination of 10 different vegetable crop seeds as tested by the standard Filter Paper Method. The seeds of eggplant and long-podded cowpea were found to be highly sensitive. The most sensitive eggplant seeds were subjected to further studies in soil. Germination percentage and the seedling vigor were drastically reduced in the presence of o-cresol even at a concentration as low as 50 mg kg−1 soil. A number of abnormalities in the seedlings such as stunted root and shoot growth, non-emergence of primary leaves, and negative geotropic growth were observed. Standard 2, 3, 5-tetrazoliumtrichloride test showed marked reduction in the viability of eggplant seeds proportionate to the concentration of o-cresol (0 through 200 mg L−1) they were exposed to, which reached zero at 175 mg o-cresol L−1, indicating the inhibition of the respiratory enzymes of the seeds. Contrary to earlier reports on the effect of phenolics on the hydrolytic enzymes of germinating seeds, in the present case an enhanced activity of amylase was observed in the presence of o-cresol (50 and 150 mg kg−1 soil), whereas the protease activity was partially inhibited at higher concentration. The inhibition of seed germination by o-cresol was revoked by bioaugmentation of the soil with the cresol-degrading Pseudomonas monteilii S-CSR-0014 (2.3 x 108 CFU g−1 wet soil) enabling normal seed germination and seedling growth. The inoculated bacterium degraded 50 and 150 mg o-cresol kg−1 soil efficiently, with concomitant growth. It can be concluded that by bacterial bioaugmentation of o-cresol-contaminated soils the inhibition of germination of crop seeds could be eliminated effectively enabling healthy seedling growth.

Effect of gamma ray irradiated pollen technique on seed development pattern in Citrus

In modern fruit breeding, to reduce the breeding cycle, induction of haploid plants through irradiated pollen technique is of paramount importance. However, the major drawback is the sensitivity of pollen to higher irradiation doses as it induces abnormality in double fertilization process. Hence, optimization of irradiation doses for maximum recovery of healthy seed is very important. Present work analyzed the seed developmental pattern of Citrus grandis, pollinated with gamma irradiated pollen (100-500 Gy) of C. limon, C. limetta, and C. sinensis. Not a single fruit was retained on the tree till maturity in C. grandis × C. limon crosses; however, in other two cross combinations, fruits were harvested at maturity only up to 300 Gy irradiation doses. Among the harvested fruit, normal seed decreased gradually with increasing irradiation doses and less than 5 normal seeds per fruit were obtained at 300 Gy with maximum in C. grandis × C. limetta cross. However, abnormal and empty number no. of seeds has increased significantly with increasing irradiation doses. Developmental pattern of embryo and endosperm within normal seeds was also influenced significantly by irradiation treatment. At higher doses, seeds number with both embryo and endosperm was decreased gradually and at 300 Gy, it was reduced to 59.47% as compared to control.

High-quality sugar production by osgcs1 rice

Carbohydrates (sugars) are an essential energy-source for all life forms. They take a significant share of our daily consumption and are used for biofuel production as well. However, sugarcane and sugar beet are the only two crop plants which are used to produce sugar in significant amounts. Here, we have discovered and fine-tuned a phenomenon in rice which leads them to produce sugary-grain. We knocked-out GCS1 genes in rice by using CRISPR technology, which led to fertilization failure and pollen tube-dependent ovule enlargement morphology (POEM) phenomenon. Apparently, the POEMed-like rice ovule (‘endosperm-focused’) can grow near-normal seed-size unlike earlier observations in Arabidopsis in which gcs1 ovules (‘embryo-focused’) were aborted quite early. The POEMed-like rice ovules contained 10–20% sugar, with extremely high sucrose content (98%). Trancriptomic analysis revealed that the osgcs1 ovules had downregulation of starch biosynthetic genes, which would otherwise have converted sucrose to starch. Overall, this study shows that pollen tube content release is sufficient to trigger sucrose unloading at rice ovules. However, successful fertilization is indispensable to trigger sucrose-starch conversion. These findings are expected to pave the way for developing novel sugar producing crops suited for diverse climatic regions.

Quantifying seed germination responses of Echinops and Centaurea, to salinity and drought stresses

Seed germination may significantly interrupt by water stress due to drought and salinity condition. Salinity can cause osmotic pressure and induce drought stress. Water deficit stress affect normal seed germination and reduce seedling vigor. The objective of this investigation was to determine the effect of drought and salt stresses on germination characteristics of Echinops ritro and Centaurea virgata. Seeds were germinated with the concentrations of sodium chloride (0, 50, 100, 150 and 200 mmol) or in polyethylene glycol PEG6000 (0, -0.2, -0.4, -0.6, -0.8, -1 and -1.2 MPa). The highest values of germination parameters were obtained with no osmotic potential or salinity stress. At treatment by PEG, the germination was severely decreased at -0.6 MPa. While, no germination occurred at- 0.8 MPa by PEG. Results revealed that under 118 Mmol salinity, the seed germination of Centaurea virgata declined to 43% which was as close as half of its total seed germination. However, 50% reduction in seed germination of Echinops ritro was observed at 193 mmol salinity. Results indicated Echinops ritro and Centaurea virgata germination was sensitive to both the stresses. However, seedling growth was more sensitive to PEG than NaCl.

Maize Defective Kernel605 Encodes a Canonical DYW-Type PPR Protein that Edits a Conserved Site of nad1 and Is Essential for Seed Nutritional Quality

Pentatricopeptide repeat (PPR) proteins involved in mitochondrial RNA cytidine (C)-to-uridine (U) editing mostly result in stagnant embryo and endosperm development upon loss of function. However, less is known about PPRs that are involved in farinaceous endosperm formation and maize quality. Here, we cloned a maize DYW-type PPR Defective Kernel605 (Dek605). Mutation of Dek605 delayed seed and seedling development. Mitochondrial transcript analysis of dek605 revealed that loss of DEK605 impaired C-to-U editing at the nad1-608 site and fails to alter Ser203 to Phe203 in NAD1 (dehydrogenase complex I), disrupting complex I assembly and reducing NADH dehydrogenase activity. Meanwhile, complexes III and IV in the cytochrome pathway, as well as AOX2 in the alternative respiratory pathway, are dramatically increased. Interestingly, the dek605 mutation resulted in opaque endosperm and increased levels of the free amino acids alanine, aspartic acid and phenylalanine. The down- and upregulated genes mainly involved in stress response-related and seed dormancy-related pathways, respectively, were observed after transcriptome analysis of dek605 at 12 d after pollination. Collectively, these results indicate that Dek605 specifically affects the single nad1-608 site and is required for normal seed development and resulted in nutritional quality relevant amino acid accumulation.