Endosperm Research Articles

Genome Wide Analysis of the Transcriptional Profiles in Different Regions of the Developing Rice Grains

BackgroundRice is an important food source for humans worldwide. Because of its nutritional and agricultural significance, a number of studies addressed various aspects of rice grain development and grain filling. Nevertheless, the molecular processes underlying grain filling and development, and in particular the contributions of different grain tissues to these processes, are not understood.Main TextUsing RNA-sequencing, we profiled gene expression activity in grain tissues comprised of cross cells (CC), the nucellar epidermis (NE), ovular vascular trace (OVT), endosperm (EN) and the aleurone layer (AL). These tissues were dissected using laser capture microdissection (LCM) at three distinct grain development stages. The mRNA expression datasets offer comprehensive and new insights into the gene expression patterns in different rice grain tissues and their contributions to grain development. Comparative analysis of the different tissues revealed their similar and/or unique functions, as well as the spatio-temporal regulation of common and tissue-specific genes. The expression patterns of genes encoding hormones and transporters indicate an important role of the OVT tissue in metabolite transport during grain development. Gene co-expression network prediction on OVT-specific genes identified several distinct and common development-specific transcription factors. Further analysis of enriched DNA sequence motifs proximal to OVT-specific genes revealed known and novel DNA sequence motifs relevant to rice grain development.ConclusionTogether, the dataset of gene expression in rice grain tissues is a novel and useful resource for further work to dissect the molecular and metabolic processes during rice grain development.

Transient Heat Stress During Early Seed Development Primes Germination and Seedling Establishment in Rice.

Rice yield is highly sensitive to increased temperature. Given the trend of increasing global temperatures, this sensitivity to higher temperatures poses a challenge for achieving global food security. Early seed development in rice is highly sensitive to unfavorable environmental conditions. Heat stress (HS) during this stage decreases seed size and fertility, thus reducing yield. Here, we explore the transgenerational phenotypic consequences of HS during early seed development on seed viability, germination, and establishment. To elucidate the impact of HS on the developmental events in post-zygotic rice seeds, we imposed moderate (35°C) and severe (39°C) HS treatments initiated 1 day after fertilization and maintained for 24, 48, or 72 h. The transient HS treatments altered the initiation of endosperm (ED) cellularization, seed size and/or the duration of spikelet ripening. Notably, seeds exposed to 24 and 48 h moderate HS exhibited higher germination rate compared to seeds derived from plants grown under control or severe HS. A short-term HS resulted in altered expression of Gibberellin (GA) and ABA biosynthesis genes during early seed development, and GA and ABA levels and starch content at maturity. The increased germination rate after 24 of moderate HS could be due to altered ABA sensitivity and/or increased starch level. Our findings on the impact of transient HS on hormone homeostasis provide an experimental framework to elucidate the underlying molecular and metabolic pathways.

Influence of milling on the nutritional composition of bran from different rice varieties.

The nutritional composition of bran from four rice varieties namely, Jyothi/IR64, Basmati and Agonibora representing high amylose, intermediate amylose and waxy, respectively were evaluated with friction and abrasive mills at different degrees of milling (DOM). Fat and protein content of the bran inversely correlated to amylose content of rice variety. The fat and fibre contents reduced with increased DOM due to increasing starch influx from the endosperm. Abrasive milling produced bran with higher protein content and total dietary fibre, resulting in superior quality bran, while friction milling led to higher fat. Agonibora bran was found to be superior in terms of nutritional quality. Industrial milling resulted in higher protein content in bran, and Jyothi variety had a better amino acid profile.

Resistencia genética a Sporisorium reilianum f. sp. zeae en líneas seleccionadas de maíz (Zea mays L.) con endospermo blanco y amarillo

<p>El carbón de la espiga (<em>Sporisorium reilianum </em>f. sp. <em>zeae</em>) del maíz (<em>Zea mays</em> L.) es una enfermedad de gran importancia que se presenta en zonas productoras de maíz, incluyendo los Valles del Mezquital y Toluca. El objetivo del presente estudio fue identificar líneas C<sub>2</sub>-S<sub>1</sub> y C<sub>2</sub>-S<sub>2</sub> de maíz adaptadas al Altiplano de México para ser utilizadas en un programa de mejoramiento de resistencia y buenas características agronómicas. Semillas de cada línea se inocularon con una suspensión de 1.7x10<sup>7</sup> mL<sup>-1</sup> teliosporas de <em>S. reilianum </em>f. sp. <em>zeae</em> en 1% de carboximetilcelulosa de sodio y se sembraron en invernadero. Las plantas fueron monitoreadas hasta la formación de espiga, donde se evaluó la incidencia. En 258 líneas C<sub>2</sub>-S<sub>1</sub> de endospermo blanco se presentó hasta 92.3% de incidencia y hasta 41.7% en 71 líneas de endospermo amarillo. Con base en la incidencia y características agronómicas, se seleccionaron y autofecundaron en campo 38 líneas C<sub>2</sub>-S<sub>1</sub> de endospermo blanco y 24 de endospermo amarillo. Un total de 123 y 114 líneas C<sub>2</sub>-S<sub>2</sub> de endospermo blanco y amarillo, respectivamente, fueron inoculadas con teliosporas del patógeno y presentaron una incidencia de la enfermedad de hasta 42.8% y 28.5%, respectivamente. La inoculación con teliosporas y siembra en invernadero permitió identificar líneas de maíz con diferente porcentaje de infección y seleccionar las líneas resistentes, probando la eficiencia de ésta técnica.</p>

Variation of starch granules in diploid species of the genus Avena L.

Composite starch granules, the main product of assimilation in oat endosperm, were analyzed in the accessions of both wild and cultivated diploid species of the genus Avena. Simple starch granules are mostly synthesized in the outer parts of the endosperm tissue. The size of sub-grains in a composite granule does not depend on a wild or cultivated status of the species. Inter-specific variation in the size differences of composite granules is large. Also, a broad variation has been detected for granules analyzed in a Lugol’s solution or polarizing light. This analysis revealed a difference between the synthesis of amylopectin versus amylose in a granule. Examples of occurrences of low levels of amylopectin synthesis are provided.

Development of ovule and relation between embryo and endosperm developments of {\sl Betula platyphylla}

Development of ovule and relation between embryo and endosperm developments of {\sl Betula platyphylla}

Vitality and germination of lemon balm ( Melissa officinalis L.) seeds

In 2012-2014, the germination ability of lemon balm seeds were tested. The investigated seeds were obtained from the lemon balm breeding project conducted at the Institute of natural Fibres & Medicinal Plants of Poznan, Poland. The germination rate was done by using ISTA seed germination rules and the high fluctuation of germination rate was observed. Low rate of germination usually disqualificates the seed material. Thus, the anatomy of the investigated lemon balm seeds was analyzed by scanning electron microscopy (SEM) and tetrazolium test was done. SEM analysis showed accurate morphological structure of all seed parts. The embryos, endosperm and testa were well and correctly developed. Seed coat was typical for all species of Lamiaceae. Abnormal seed part were not found. Tetrazolium test revealed the high rate of vitality of the investigated strain seeds. Thus, other useful tests should be recommended before seed disqualification will be done in case of low germination rate.

Identificación de almidones de maíces catamarqueños: aplicación a dos casos arqueológicos.

En este trabajo presentamos un modelo estadístico para discriminar tipos de maíz a partir de los gránulos de almidón arqueológicos que fueron recuperados en vasijas cerámicas e implementos de molienda de piedra. El modelo fue generado a partir del estudio de una amplia base de datos de gránulos de almidón de maíces nativos del Noroeste argentino. Se llevó a cabo un Análisis Discriminante utilizando el método de inclusión por pasos. Este análisis nos permitió asignar los ejemplares arqueológicos a los diferentes tipos de maíz, definidos por su textura de endosperma: córneo, harinoso, dextrinoso, dentado y córneo harinoso. La identificación de tipos de maíz en las muestras arqueológicas permitió discutir las potenciales prácticas de preparación y consumo de alimentos y bebidas catamarqueñas en tiempos prehispánicos.

Metabolomics study of cereal grains reveals the discriminative metabolic markers associated with anatomical compartments

This study used NMR-based metabolomics to compare the metabolic profile of different anatomical compartments of cereal grains i.e. bran and endosperm in order to gain further insights into their possible role in the beneficial health effects of whole grain products (WG). Polar water-soluble metabolites in 64 bran and endosperm, samples from rye and wheat were observed using 600 MHz NMR. Bran samples had higher contents of 12 metabolites than endosperm samples. A comparative approach revealed higher contents of azelaic acid and sebacic acid in bran than in endosperm. In a pilot study, the consumption of WG rye bread (485 g) caused NMR signals in 24h urine corresponding to azelaic acid. The relatively high abundance, anatomical specificity, pattern of metabolism, urinary excretion in human, antibacterial, and anticancer activities suggest further studying of azelaic acid when exposure to WG or beneficial effects of WG are investigated.

Variability of barley aleurone layer induced by X-rays

A series of Hordeum vulgare cultivars was irradiated by X-rays to induce mutations in endosperm. Many structural defects of endosperm were revealed in plants irradiated 8 DAF. Change of a cell cycle was especially frequent and this was visible in the form of clones of small or large cells in the aleurone layer. X-irradiation appeared as a successful tool in the study of development.

Preliminary studies on plants regenerated from endosperm-derived callus of kiwifruit (Actinidia deliciosa var. deliciosa)

To show differences between plants of Actinidia deliciosa var. deliciosa regenerated from endosperm-derived callus (with 3C amounts of DNA) and those obtained from seeds, observation of their stomata and leaf hairs density was carried out. Stomata and leaf hairs are the features which are often related to ploidy status of plants. Our observation revealed that for plants, which represents 3C DNA level, stomata density was higher than for plantlets showing 2C DNA content. Additionally, density of leaf hairs seems to be also higher in regenerants. This is the first morpho-histological studies of plants regenerated from kiwifruits endosperm tissue.

Observation Process of Free Nuclei Division and Cellularization in Ginkgo biloba L. Endosperm

Observation Process of Free Nuclei Division and Cellularization in Ginkgo biloba L. Endosperm

Sucrose metabolism in coffee submitted to different shade levels

The objective of this study was to evaluate the activity of the enzymes involved in the sucrose metabolism and the carbohydrate levels on the endosperm of the coffee fruit under different shade levels. Four replicater were used, totaling 20 plots, which consisted of eight useful plants. Treatments were arranged in a randomized block design in a 5 x 3 factorial outline, being five shade levels (full sun, 35, 50, 65 and 90% shade) and three fruit development stages (green, green-yellow and cherry). The variables analyzed were the activities of the enzymes sucrose-phosphate synthase (SPS), sucrose synthase (SuSy) and acid invertase and total soluble sugars, sucrose and glucose content. The shading higher than 50% increased the activity of acid invertase and SuSy in green-yellow and cherry stages. Regarding the SPS, shading did not alter its activity, the highest values were found in the green-yellow and cherry stages. The shading levels up to 65% have the highest soluble sugar levels and sucrose in the late stages of maturation while for the 90% shading, the highest values were found in the early stages of fruit development. The glucose content was higher in the green maturation stage, up to the level of 50% shading, from which there is a decrease in glucose values with increased shading. Thus, it appears that shading higher than 50%, probably modifies the fruit development by affecting the metabolism of sucrose in the endosperm, prolonging the maturation period.

Proteome balancing of the maize seed for higher nutritional value.

Most flowering plant seeds are composed of the embryo and endosperm, which are surrounded by maternal tissue, in particular the seed coat. Whereas the embryo is the dormant progeny, the endosperm is a terminal organ for storage of sugars and amino acids in proteins and carbohydrates, respectively. Produced in maternal leaves during photosynthesis, sugars, and amino acids are transported to developing seeds after flowering, and during germination they nourish early seedlings growth. Maize endosperm usually contains around 10% protein and 70% starch, and their composition ratio is rather stable, because it is strictly regulated through a pre-set genetic program that is woven by networks of many interacting or counteracting genes and pathways. Endosperm protein, however, is of low nutritional value due mainly to the high expression of the α-zein gene family, which encodes lysine-free proteins. Reduced levels of these proteins in the opaque 2 (o2) mutant and α-zein RNAi (RNA interference) transgenic seed is compensated by an increase of non-zein proteins, leading to the rebalancing of the nitrogen sink and producing more or less constant levels of total proteins in the seed. The same rebalancing of zeins and non-zeins has been observed for maize seeds bred for 30% protein. In contrast to the nitrogen sink, storage of sulfur is controlled through the accumulation of specialized sulfur-rich proteins in maize endosperm. Silencing the synthesis of α-zeins through RNAi fails to raise sulfur-rich proteins. Although overexpression of the methionine-rich δ-zein can increase the methionine level in seeds, it occurs at least in part at the expense of the cysteine-rich β- and γ-zeins, demonstrating a balance between cysteine and methionine in sulfur storage. Therefore, we propose that the throttle for the flow of sulfur is placed before the synthesis of sulfur amino acids when sulfur is taken up and reduced during photosynthesis.

The in vitro development of isolated rye proembryos

Isolated 7 day-old rye proembryos, 130-150 µm long, which were inoculated directly onto a medium, degenerated by 100%. Proembryos of the same size, introduced into culture using nurse endosperm, survived by 74%, from which 64% developed normally, giving green and rooted plants.

“CANDIDATUS LIBERIBACTER ASIATICUS”, ASSOCIATED WITH CITRUS HUANGLONGBING, INFECTS POLLEN, SEED COAT AND ENDOSPERM OF PUMMELO IN CHINA

“Candidatus Liberibacter asiaticus” (Las), one of the three known bacterial species associated with citrus Huanglongbing (HLB), is unevenly distributed in bark tissue, leaf midrib, roots, and different floral parts of infected citrus trees. In this study, 10 petal, 12 stamen, 12 pistil, 3 pollen, 20 seed hull, 20 seed coat and 20 endosperm samples were collected from HLB-infected Shatianyou pummelo trees [= Citrus maxima (Burm.) Merr. cv. Shatian Yu] in China and analyzed for the presence of Las. The bacterium was detected by conventional PCR using the Las-specific primer pair OI1/OI2c. Amplification products of the expected size (ca. 1100 bp) were obtained from 9 petal (90%), 11 stamen (91.7%), 12 pistil (100%), 2 pollen (66.7%), 18 seed coat (90%), 15 endosperm (75%) samples, but not from any of the seed hull samples. The sequence of a representative amplicon matched that of Las. To our knowledge, this is the first report of the presence of Las in pollen, seed coat and endosperm of pummelo in China.

Seed traits evaluation from long-term selection of kernel oil concentration in a high-oil maize population KYHO

Wang, H.-W., Hu, H.-X., Song, T.-M. and Chen, S.-J. 2012. Seed traits evaluation from long-term selection of kernel oil concentration in a high-oil maize population KYHO. Can. J. Plant Sci. 92: 857-866. A high-oil maize population, KYHO, was developed over 10 generations by selective breeding for increased kernel oil content (KOC). The objectives of this study were to evaluate kernel oil selection effects, and measure the trait changes and genetic variance in the embryo and endosperm. Oil, protein, and starch content in the embryo and endosperm were estimated by near-infrared reflectance spectroscopy (NIRS). Mass and volume of embryo and endosperm were measured. Selective breeding increased embryo oil content (EMOC) and endosperm oil content (ENOC), especially EMOC, which changed from 315.62 g kg-1 C0 to 592.54 g kg-1 C10, resulting in an increase in total embryo and endosperm oil content (EEOC) from 43.32 g kg-1 C0 to 139.95 g kg-1 C10. With selection for increase in EEOC, embryo protein content (EMPC) d...

Morphological characterization of triticale starch granules during endosperm development and seed germination

Li, C.-Y., Li, W.-H., Lee, B., Laroche, A., Cao, L.-P. and Lu, Z.-X. 2011. Morphological characterization of triticale starch granules during endosperm development and seed germination. Can. J. Plant Sci. 91: 57-67. The morphology of starch granules and its changes during endosperm development and seed germination in triticale has been investigated under scanning electron microscopy (SEM). Starch granules were rapidly accumulating in triticale endosperm after 6 d postanthesis (DPA). The double-disk structure of starch granules was detected in endosperms from 6 DPA until 27 DPA in triticale and its parental crops, wheat and rye. The equatorial grooves of triticale starch granules were more susceptible to enzymatic hydrolysis than the broad or flat surfaces. Triticale starch was slowly degraded within 4 or 5 d post germination (DPG) and most starch granules were almost completely hydrolyzed after 9 DPG. Morphological changes of starch granules observed under SEM during the in vitro enzymatic hydrolysis were...

IMPACT OF THE SEED-BORNE STAGE OF RAMULARIA COLLO-CYGNI IN BARLEY SEED

Ramularia collo-cygni (Rcc) infects spring and winter barley causing Ramularia leaf spot (RLS). During 2009 and 2010, contrasting years for the natural occurrence of RLS in the Czech Republic, infestation intensity was assessed with field experiments at two locations in relation to Ramularia contamination of seeds. A real time PCR assay was designed to quantify the pathogen in barley tissues. PCR primers and a TaqMan probe were designed to target Rcc-specific DNA sequence. The method was optimized using pure fungal DNA and plasmid standard dilutions. After washing, kernels were dissected into lemma, pericarp, testa, endosperm and embryo which were individually tested by real time PCR for quantifying Rcc, whereas the presence of other potential seed-borne pathogens was checked by standard PCR. The level of seed contamination was not the main factor influencing symptom expression. In 2009, seeds with low Rcc contamination were planted in two locations in both of which severe RLS infection had occured. In 2010, seeds with higher Rcc contamination were planted, but the extent of RLS symptoms on the leaves was much lower. Rcc occurred at higher rates in kernels from the 2009 crop, when RLS was severe. Ramularia DNA was highest in the lemma, and occurred in lower amounts in the pericarp and embryo. It was also found in the water used for washing the kernels. The results showed that Rcc does not penetrate through the testa into the endosperm.

Robbrechtia, a New Rubiaceae Genus from Madagascar

Two new Rubiaceae species, Robbrechtia grandifolia and R. milleri from Madagascar are described. Clearly belonging to the tribe Pavetteae, the species possess an unusual combination of characters (sheathing stipules with intra- petiolar lobes, young shoots and inflorescence parts covered with copious colleter exudate, long-tubed flowers with a well- developed calyx, a bilobed stigma and unilocular fruits with a single, deeply ruminate seed) that makes the establishment of a new genus, Robbrechtia, necessary. Detailed descriptions, illustrations and distribution data of the new taxa are given. The characters of the genus are evaluated and compared to those of the other representatives of the tribe Pavetteae. During field work for a survey of the Pavetteae from Madagascar a tree bearing fruit was collected (Davis 2210) in the Moramanga area, ca. 75 km east of An- tananarivo. With its large leaves and stipules, its size- able fruits with persistent large calyx and the pubes- cence of the vegetative parts, the plant's habit closely resembled that of the genus Homolliella (Rubiaceae, tribe Pavetteae), represented in that area by two spe- cies. However, upon dissection the fruit proved to be unilocular with one deeply ruminate seed, very differ- ent from the fruit of Homolliella but not unlike that of several other genera of the Pavetteae. A subsequent survey of herbaria uncovered a group of undetermined specimens sharing a striking character combination, unique in the Pavetteae: sheathing stipules with intra- petiolar lobes, young shoots and inflorescence parts covered with copious colleter exudate, long-tubed flowers with a well-developed calyx, a bilobed stigma, unilocular, one-seeded fruits, and seeds with deeply ruminate endosperm. Moreover, this character combi- nation occurred in two previously undescribed species. They are here accommodated in a new genus, Robbrech- tia, named in honour of Prof. Dr. Elmar Robbrecht (Na- tional Botanic Garden of Belgium), who has dedicated his professional life to the study of the Rubiaceae. In Madagascar the Rubiaceae are the second largest family of flowering plants, represented by ca. 100 gen- era and 800-1,000 species. Despite the size of the fam- ily and its strong representation in all vegetation types on the island, the Malagasy Rubiaceae are very poorly known. Recent treatments exist only for a small num- ber of genera and even at the generic level identifica- tion remains difficult in certain tribes, e.g. the Octotro- pideae, Vanguerieae and the Pavetteae. The tribe Pavetteae A.Rich. ex Dumortier was re- vived by Robbrecht (1984) to accommodate all repre- sentatives of the subfamily Ixoroideae formerly placed in Coffeeae s.l. and Gardenieae possessing terminal in- florescences, 3- or 4-colporate tectate pollen grains, drupaceous fruits, seeds with an adaxial excavation surrounded by an annulus and exotestal cells either parenchymatic or with thickenings along the outer tan- gential wall. A detailed study stressing the importance of fruit, seed and seed-coat characters was later exe- cuted by Bridson and Robbrecht (1985). These authors proposed an informal classification of the tribe into two groups, notably genera related to Ixora and genera related to Tarenna. Recently, Andreasen & Bremer (1997; 2000) resurrected the tribe Ixoreae to accom- modate Ixora and its closest allies. The newly delimited tribes Ixoreae and Pavetteae share the following char- acters: woody habit, absence of raphides, entire stip- ules (but fimbriate in Rutidea), terminal inflorescences, contorted aestivation, drupaceous fruits and secondary pollen presentation. They differ in characters such as number of ovules per locule, structure of the stigma, shape of the thickenings of the exotestal cells, etc. An overview of these differences is given in Table 1. In the following text, the tribe Pavetteae is used as delimited by Andreasen & Bremer (1997; 2000). Only ca. seventy species of Pavetteae occur in Mad- agascar but endemism at the specific level is 98%. Of the six genera currently recognized in Madagascar, three are endemic: Homollea (three species; Arenes 1960), Homolliella (five species; De Block, unpubl. data) and Schizenterospermum (four species; Arenes 1960). The paleotropical genus Tarenna is represented in Madagascar with ca. 10 species. Other representatives of the Pavetteae are the Afro-Malagasy genera Coptos- perma (ca. 37 species in Madagascar: De Block, unpubl. data) and Paracephaelis (ca. seven species; De Block, un- publ. data). Coptosperma was recently newly delimited to include Enterospermum (De Block et al. 2002). Generic delimitation is still under discussion for the Malagasy representatives of the Pavetteae. One of the main discussion points is the taxonomic importance of ruminate endosperm, a character present in ca. 60% of the Malagasy Pavetteae against 17% for the continental African species. Botanists studying Malagasy Pavet- teae recognized two main genera, notably Tarenna (en- tire endosperm) and Enterospermum (ruminate endo- sperm) (Homolle 1938; Capuron 1973). Botanists fo-