Aleurone Cells Research Articles

TaABI5, a wheat homolog of Arabidopsis thaliana ABA insensitive 5, controls seed germination

Abscisic acid (ABA) response element (ABRE)-binding factors (ABFs) are basic region/leucine zipper motif (bZIP) transcription factors that regulate the expression of ABA-induced genes containing ABRE in their promoters. The amino acid sequence of the wheat bZIP protein, TaABI5, showed high homology to that of Arabidopsis ABA insensitive 5 (ABI5). TaABI5 was classified into the clade of ABI5s in Arabidopsis and rice, unlike TRAB1 of rice, Wabi5 of wheat, and HvABI5 of barley in the bZIP Group A family, by a phylogenetic analysis. TaABI5 was strongly expressed in seeds during the late ripening and maturing stages; however, its expression level markedly decreased after germination. An in situ hybridization analysis showed that TaABI5 mRNA accumulated in seed embryos, particularly the scutellum. In a transient assay using wheat aleurone cells, TaABI5 activated the promoter of Em containing ABRE, which is an embryogenesis abundant protein gene, indicating that TaABI5 acts as a transcription factor in wheat seeds. Furthermore, the seeds of transgenic Arabidopsis lines introduced with 35S:TaABI5 exhibited high sensitivity to ABA and the inhibition of germination. The seed dormancy of the transgenic Arabidopsis lines was stronger than that of Col. These results support TaABI5 playing an important role in mature seeds, particularly before seed germination, and acting as a functional ortholog to Arabidopsis ABI5.

Reticulon proteins modulate autophagy of the endoplasmic reticulum in maize endosperm.

Reticulon (Rtn) proteins shape tubular domains of the endoplasmic reticulum (ER), and in some cases are autophagy receptors for selective ER turnover. We have found that maize Rtn1 and Rtn2 control ER homeostasis and autophagic flux in endosperm aleurone cells, where the ER accumulates lipid droplets and synthesizes storage protein accretions metabolized during germination. Maize Rtn1 and Rtn2 are expressed in the endosperm, localize to the ER, and re-model ER architecture in a dose-dependent manner. Rtn1 and Rtn2 interact with Atg8a using four Atg8-interacting motifs (AIMs) located at the C-terminus, cytoplasmic loop, and within the transmembrane segments. Binding between Rtn2 and Atg8 is elevated upon ER stress. Maize rtn2 mutants display increased autophagy and up-regulation of an ER stress-responsive chaperone. We propose that maize Rtn1 and Rtn2 act as receptors for autophagy-mediated ER turnover, and thus are critical for ER homeostasis and suppression of ER stress.

The Modular Control of Cereal Endosperm Development.

Expansion of the human population demands a significant increase in cereal production. The main component of cereal grains is endosperm, a body of starchy endosperm (SE) cells surrounded by aleurone (AL) cells with transfer cells (TC) at the base and embryo surrounding (ESR) cells adjacent to the embryo. The data reviewed here emphasize the modular nature of endosperm by first suggesting that sucrose promotes development of the fertilized triploid endosperm cell. Next, that the basal syncytial endosperm responds to glucose by turning on TC development. The default endosperm cell fate is SE and ESR differentiation is likely activated by signaling from the embryo. Cells on the exterior surface of the endosperm are specified as AL cells.

Variation in cell wall structure and composition of wheat grain based on geography and regulatory effect of cell wall on water mobility.

Wheat grain from 12 different regions in China was used to study variations in the cell wall structure and chemical composition based on geography. The mobility and migration rate of water in wheat grain during moisture absorption and drying were determined under different relative humidity conditions. Depending on the geography, variations were noted in the thickness and component content of the wheat grain cell wall. Cell wall thickness was positively correlated with the total arabinoxylan (TAX) content. Cell wall thickness and TAX content of the aleurone layer were positively correlated with altitude and negatively correlated with longitude. The water migration rate decreased with the increase of cell wall thickness and TAX content. Nuclear magnetic resonance (NMR) results revealed that grains with thick aleurone cell wall showed increased molecular mobility of water. These findings lay the foundation for further study of water regulation in wheat cell wall.

Staining of RNA and DNA on electrophoretic gels and in cytology with juice of Vaccinium myrtillus berries

BackgroundMy early results of cytological chromosome staining with berry juice of blueberry or bilberry (Vaccinium myrtillus) was re-evaluated with staining of electrophoretic agarose and polyacrylamide gels, fractionating DNA, RNA, and proteins. ResultsElectrophoretic gels were stained with juice from berries of V. myrtillus, only filtered, or the diluted filtrate was mixed with acetic acid and 2-propanol. The staining starts in 2 min, with the highest intensity over the background usually appearing in about 30 min. The berry juice stains RNA, DNA, and an unidentified contaminant of molar mass 200–700 g. After differentiation of the gel background, the stained zones appear purple or black. The berry juice staining with or without acetic 2-propanol shows sharp RNA and DNA zones on gels in Vis (visible) light, and the berry juice displaces a preceding staining with ethidium bromide. A secondary staining with ethidium bromide is not able to displace the berry juice in nucleic acids. Cytological staining of sectioned mature barley (Hordeum vulgare) grains with Vaccinium myrtillus juice followed by differentiation in dilute acetic acid shows nuclei and apparent RNA storing compartments in the aleurone cells and stains suberin-containing chalazal cells of the grain crease deeply red, which keeps long. The anthocyanins faintly stain some proteins on gels. The preparation of polymers from cytochrome c and myoglobin was described. ConclusionsThe staining molecules of V. myrtillus anthocyanins apparently intercalate in the nucleic acids competing for the sites, which could be intercalated by ethidium bromide. The juice is suggested to have use in the exchange of intercalating toxic molecules from DNA and RNA, in the inactivation of viruses, and phytotherapy. The juice may have a use as a nontoxic stain in cytology.

Steeping and germination of wheat (Triticum aestivum L.). I. Unlocking the impact of phytate and cell wall hydrolysis on bio-accessibility of iron and zinc elements

In wheat aleurone cells iron and zinc ions occur as phytate structures. Phytate and arabinoxylan cell wall material resist digestion in the human gastro-intestinal tract resulting in very low mineral bio-accessibility. During wheat germination, enzymes make nutrients available for plant development and, when used in foods, for human uptake. We here provide understanding of the impact of the wheat matrix on mineral bio-accessibility. A multifactor experiment in which wheat was subjected to multiple combinations of steeping time (8–36 h), steeping temperature (15–40 °C), germination time (0–120 h) and germination temperature (15–30 °C) showed that steeping for 36 h at 15 °C and germination for 120 h at 26 °C decreased phytate content from 0.96% to 0.65% of initial dry matter (idm) and increased water extractable arabinoxylan content from 0.48% to 1.34% of idm due to phytase and endoxylanase action, respectively. While the iron and zinc bio-accessibility in the wheat grains was 5 and 3%, respectively, that in the germinated grains was 6 and 8% when the cellular matrix was preserved, and 22 and 21% when it was mechanically disrupted. This study thus revealed that controlled steeping and germination of wheat can substantially improve mineral bio-accessibility when the cell walls are broken down.

Overexpression of HvCslF6 in barley grain alters carbohydrate partitioning plus transfer tissue and endosperm development.

In cereal grain, sucrose is converted into storage carbohydrates: mainly starch, fructan, and mixed-linkage (1,3;1,4)-β-glucan (MLG). Previously, endosperm-specific overexpression of the HvCslF6 gene in hull-less barley was shown to result in high MLG and low starch content in mature grains. Morphological changes included inwardly elongated aleurone cells, irregular cell shapes of peripheral endosperm, and smaller starch granules of starchy endosperm. Here we explored the physiological basis for these defects by investigating how changes in carbohydrate composition of developing grain impact mature grain morphology. Augmented MLG coincided with increased levels of soluble carbohydrates in the cavity and endosperm at the storage phase. Transcript levels of genes relating to cell wall, starch, sucrose, and fructan metabolism were perturbed in all tissues. The cell walls of endosperm transfer cells (ETCs) in transgenic grain were thinner and showed reduced mannan labelling relative to the wild type. At the early storage phase, ruptures of the non-uniformly developed ETCs and disorganization of adjacent endosperm cells were observed. Soluble sugars accumulated in the developing grain cavity, suggesting a disturbance of carbohydrate flow from the cavity towards the endosperm, resulting in a shrunken mature grain phenotype. Our findings demonstrate the importance of regulating carbohydrate partitioning in maintenance of grain cellularization and filling processes.

Steeping and germination of wheat (Triticum aestivum L.). II. Changes in spatial distribution and speciation of iron and zinc elements using pearling, synchrotron X-ray fluorescence microscopy mapping and X-ray absorption near-edge structure imaging

Iron (Fe) and zinc (Zn) in wheat are mainly present as insoluble phytates in the aleurone cells. Phytate breakdown during steeping and germination of wheat enhances their bio-accessibility. However, the accompanying redistribution within the grain and changes in speciation are still unclear. We unravelled these changes using a combination of wheat fractionation by pearling, X-ray fluorescence microscopy mapping and X-ray absorption near-edge structure imaging. A significant fraction of Zn and Fe migrates to radicles and coleoptiles during germination. The remainder has low water extractability (≤8%). The high water extractability (26–27%) of Zn in the radicle and coleoptile indicates its mobility in the seedling. Zn migrates from the aleurone to the pericarp and embryonic tissues, while Fe is dominantly present in the scutellum tissue attached to the seedling. The co-localisation of Zn and sulfur (S) in the developing embryo suggests that translocated Zn is bound to S-containing peptides. In aleurone cells Fe remains phytate bound and although Zn is phytate and S-bound, slight changes in its speciation occur during germination. This study partially explains the impact of steeping and germination on mineral bio-accessibility and opens possibilities for enhancing nutritional quality during food processing.

Aleurone cells are the primary contributor to arabinoxylan oligosaccharide production from wheat bran after treatment with cell wall‐degrading enzymes

SummaryArabinoxylans and in particular arabinoxylan oligosaccharides (AXOS) from wheat are recognised for their prebiotic potential. A high‐yield, non‐chemical production of AXOS is therefore of interest when producing functional foods. This study investigated the enzymatic production of AXOS from wheat bran with the aim of establishing the main fraction contributing to production of AXOS. Fractions of wheat bran, outer pericarp and aleurone with two different purities were treated with the cell wall‐degrading enzymes: xylanase, cellulase and β‐glucanase. The yield of solubilised arabinoxylans upon treatment was greatest in the most pure aleurone fraction (164 g kg−1) and lowest in the outer pericarp fraction (15 g kg−1). The yield was mainly recovered as AXOS rather than soluble arabinoxylans and was negatively related to the arabinose/xylose ratio found in the raw material. In conclusion, wheat aleurone cell walls are the main contributor to the production of AXOS from wheat bran and this seems to depend on the A/X ratio of the raw material.

Morphological characteristics of endosperm in different regions of maize kernels with different vitreousness

The vitreous and floury endosperms have regional distributions in maize kernels, and influence their qualities and applications. In this study, the whole transverse and longitudinal sections of maize mature dent, flint, and pop kernels were observed to reveal and compare the morphological characteristics of cell, starch, and protein in different regions of endosperm. The shape and size of cells had significant differences in different regions of dent and flint maize endosperms, but had no relationship with vitreous and floury texture. Popcorn had homogeneously polygonal cells in whole endosperm. The vitreous endosperm in middle and central regions of kernel had polygonal starch granules with large size and that close to aleurone cells had spherical granules with small size, but the floury endosperm had only spherical granules with different sizes. The shape and size of starch granules did not directly determine the texture of vitreous and floury endosperm. The storage protein was distributed regionally in endosperm, and its content and spatial distribution was related with vitreous endosperm. The above results not only enriched our knowledge of vitreous and floury endosperms of maize, but also provided some information for quality breeding and applications of maize kernels with different vitreousness.

Transcriptional regulatory activity of the cereal grain bZip protein TaABF1 can be either stimulated or inhibited by phosphorylation

AbstractThe wheat bZip transcription factor TaABF1 mediates both abscisic acid (ABA)-induced and ABA-suppressed gene expression. As levels of TaABF1 protein do not change in response to ABA, and TaABF1 is in a phosphorylated statein vivo, we investigated whether TaABF1 could be regulated at the post-translational level. In bombarded aleurone cells, a TaABF1 protein carrying phosphomimetic mutations (serine to aspartate) at four sites (S36D, S37D, S113D, S115D) was three to five times more potent than wild-type TaABF1 in activatingHVA1, an ABA-responsive gene. The phosphomimetic mutations also increased the ability of TaABF1 to downregulate the ABA-suppressed geneAmy32b. These findings strongly suggest that phosphorylation at these sites increases the transcriptional regulatory activity of TaABF1. In contrast to the activation observed by the quadruple serine to aspartate mutation, a single S113D mutation completely eliminated the ability of TaABF1 to upregulateHVA1or downregulateAmy32b. Thus phosphorylation of TaABF1 can either stimulate or inhibit the activity of TaABF1 in regulating downstream genes, depending on the site and pattern of phosphorylation. Mutation of S318 and S322 (in the bZIP domain) eliminated the ability of TaABF1 to activateHVA1, but had no effect on the ability of TaABF1 to downregulateAmy32b, suggesting that TaABF1 repressesAmy32bexpression through a mechanism other than direct DNA binding. An important step towards understanding how ABA and gibberellin (GA) signals are integrated through TaABF1 phosphorylation to regulate downstream gene expression is to clarify the effects of those hormones on the expression of specific genes. In contrast to some other ABA-induced genes, we found thatHVA1induction by ABA or TaABF1 is not inhibited by GA.

Structural features of the aleurone layer of the seed coat associated with imbibition injury in soybean.

Soybean (Glycine max) seeds are prone to imbibition injury caused by a rapid uptake of water. Genetic variation in imbibition injury tolerance is well documented, but the underlying mechanisms remain unclear. The aim of this study was to clarify the role of the aleurone layer of seed coat in the tolerance and its structural differences between tolerant and susceptible cultivars. Imbibition injury tolerance was closely related to the water absorption rate of seeds, which was regulated by the aleurone layer of the seed coat. Cryo-scanning electron microscopy analysis revealed that water absorbed in seed coats entered the seed preferentially through the aleurone layer of the top area above the raphe. In susceptible cultivars, the cell walls of the aleurone layer facing the cotyledon in this area were thin and the surface showed shallow depression-like structures, a distinct structure different from those of the tolerant cultivars, which had aleurone cells with thick outer cell walls and smooth and stripe-like deposits. The differences in the structural features of the cell walls and surfaces of aleurone cells in the top area of the seed may be responsible for the difference in the extent of imbibition injury between susceptible and tolerant cultivars.

Identification of Long Noncoding RNAs in the Developing Endosperm of Maize.

Maize endosperm consists of three distinct types of tissues, including the starchy endosperm (SE), the basal endosperm transfer cell layer (BETL), and the aleurone cell layer (AL). Compartmentalization of these tissues during endosperm differentiation makes the endosperm development an excellent model to study changes in gene expression during development. By utilizing cryo-dissection of developing endosperm, morphologically distinct samples can be obtained for transcriptome and epigenome analysis. Here, we describe methods for the isolation of tissues from developing maize endosperm and for the transcriptome analysis to identify novel long noncoding RNAs. The transcriptome data can be further analyzed to illustrate spatiotemporal changes in both coding and noncoding transcripts during the endosperm development.

Laser Microdissection-Based Tissue-Specific Transcriptome Analysis Reveals a Novel Regulatory Network of Genes Involved in Heat-Induced Grain Chalk in Rice Endosperm.

Heat stress occurrence during seed filling leads to the formation of a chalky portion in the limited zone of the starchy endosperm of rice grains. In this study, isolation of aleurone, dorsal, central and lateral tissues of developing endosperm by laser-microdissection (LM) coupled with gene expression analysis of a 44 K microarray was performed to identify key regulatory genes involved in the formation of milky-white (MW) and white-back (WB) grains during heat stress. Gene regulatory network analysis classified the genes changed under heat stress into five modules. The most distinct expression pattern was observed in modules where most of the small heat shock proteins and cellular organization genes were changed under heat stress in dorsal aleurone cells and dorsal starchy endosperm zones. The histological observation supported the significant increase in cell number and size of dorsal aleurone cells in WB grains. With regard to the central starchy endosperm zone, preferential down-regulation of high molecular weight heat shock proteins (HMW HSPs), including a prominent member encoding endoplasmic reticulum (ER) chaperones, by heat stress was observed, while changes in expression of starch biosynthesis genes were minimal. Characterization of transgenic plants suppressing endosperm lumenal binding protein gene (BiP1), an ER chaperone preferentially down-regulated at the MW zone under heat stress, showed evidence of forming the chalky grains without disturbing the expression of starch biosynthesis genes. The present LM-based comprehensive expression analysis provides novel inferences that HMW HSPs play an important role in controlling redox, nitrogen and amino acid metabolism in endosperm leading to the formation of MW and WB chalky grains under heat stress.

Plant Stature Related receptor-like Kinanse2 (PSRK2) acts as a factor that determines stem elongation toward gibberellins response in rice.

Gibberellins (GAs) are a family of plant hormones that are important to multiple aspects of plant growth and development, especially stem elongation. A PSRK2 was obtained through screening and identifying RLK dominant negative mutants. Phenotype of the loss-of-function mutants, psrk2-DN and psrk2-RNAi, showed that PSRK2 could influence the length of the uppermost and fourth internodes, indicating that PSRK2 might regulate cell division in the intercalary meristems and/or cell elongation in the internodes. Moreover, the expression pattern showed that PSRK2 was strongly expressed in the joined-nodes after the start-up of reproductive growth, but undetectable in leaves. PSRK2 expression was also found to be induced by GA3, and PSRK2 was involved in GA signaling in cereal aleurone cells, and PSRK2 influence the relative length of the second leaf sheaths in seedling stage. These results indicate PSRK2 is a component of GA signaling pathway that controls stem elongation by negatively regulating GA responses. Abbreviations: Os: Oryza sativa; At: Arabidopsis thaliana; RNAi: RNA interfere; DN: Dominate Negative; SMART: Simple Modular Architecture Research Tool; Uni : Uniconazol; PSRK2: Plant Stature Related receptor-like Kinase 2; RLK: Receptor-like Kinase; GA: Gibberellin; IAA: indole-3-acetic acid; BL: Brassinosteroid.

Specific region affects the difference in accumulation levels between apple food allergen Mal d 1 and birch pollen allergen Bet v 1 which are expressed in vegetative tissues of transgenic rice.

Specific domain of the Mal d 1 was identified to be mainly involved in higher accumulation level in vegetative tissues of transgenic rice than the Bet v 1. Apple food allergen Mal d 1 and birch pollen allergen Bet v 1 belong to the same pathogen related protein 10 (PR10) family. When green fluorescent protein (GFP) fused to either of these allergens was expressed as a secretory protein in transgenic rice by ligating an N terminal signal peptide and a C terminal KDEL ER retention signal under the control of the maize ubiquitin constitutive promoter, the GFP:Mald1 highly accumulated in various tissues, whereas accumulation level of the GFP:Betv1 was remarkably reduced in vegetative tissues except for seed. Analysis by RT-PCR exhibited that there was little difference in their transcript levels, indicating the involvement of post-transcriptional regulation. To investigate the cause of such difference in accumulation levels, deletion analysis of the Mal d 1 and domain swapping between them were carried out in transgenic rice. The results showed that the region between positions 41-90 in the Mal d 1 is predominantly implicated in higher level accumulation in vegetative tissues as well as seed as compared with the Bet v 1. The GFP:Mald1 was localized in oligomeric form within ER lumen or ER-derived particles in vegetative tissues, whereas in seed mainly deposited into novel huge ER-derived protein bodies with the size of 5-10µm in aleurone cells.

Mutations in the DNA demethylase OsROS1 result in a thickened aleurone and improved nutritional value in rice grains.

The rice endosperm, consisting of an outer single-cell layer aleurone and an inner starchy endosperm, is an important staple food for humans. While starchy endosperm stores mainly starch, the aleurone is rich in an array of proteins, vitamins, and minerals. To improve the nutritional value of rice, we screened for mutants with thickened aleurones using a half-seed assay and identified thick aleurone 2-1 (ta2-1), in which the aleurone has 4.8 ± 2.2 cell layers on average. Except for starch, the contents of all measured nutritional factors, including lipids, proteins, vitamins, minerals, and dietary fibers, were increased in ta2-1 grains. Map-based cloning showed that TA2 encodes the DNA demethylase OsROS1. A point mutation in the 14th intron of OsROS1 led to alternative splicing that generated an extra transcript, mOsROS1, with a 21-nt insertion from the intron. Genetic analyses showed that the ta2-1 phenotype is inherited with an unusual gametophytic maternal effect, which is caused not by imprinted gene expression but rather by the presence of the mOsROS1 transcript. Five additional ta2 alleles with the increased aleurone cell layer and different inheritance patterns were identified by TILLING. Genome-wide bisulfite sequencing revealed general increases in CG and CHG methylations in ta2-1 endosperms, along with hypermethylation and reduced expression in two putative aleurone differentiation-related transcription factors. This study thus suggests that OsROS1-mediated DNA demethylation restricts the number of aleurone cell layers in rice and provides a way to improve the nutrition of rice.

Maize miniendosperm proliferation in vitro is characterized by tracheary element formation

Maize grain is of a great economic importance worldwide. Morphometric and cytological descriptions of developing maize endosperms are available in inbred lines growing under natural conditions. Despite tremendous potential in biotechnology, similar studies focused on endosperm development in vitro are rather rare. Here we provide a comparative study on growth and development of endosperms in planta versus in vitro, considering regulation by different cytokinins during endosperm cultivation. Histochemical analyses were performed on hand-cut sections of samples stained with Sudan III. Microtubules (MTs) were immunolocalized in whole mount samples and Steedmanʼs wax sections of endosperm and miniendosperm from in vitro conditions. Our results confirmed that in vitro cultured maize endosperms proliferate and establish aleurone and starchy cells like endosperms grown in planta, however later ones undergo a distinct developmental program triggered/controlled by cytokinins. Higher mitotic activity of surface layer cells resulted in the miniendosperm proliferation, while the centrally localized parenchymatic starchy-like cells differentiated into tracheary elements (TEs). Furthermore, we report, for the first time, on the formation of numerous lobes and trichomes on pericarp cells. MT rearrangements play an important regulatory role in the differentiation of TEs. Formation of functional vascular tissue and lipid accumulation appears to be fundamental for maize miniendosperm proliferation. In contrast, the presence of maternal tissue (pericarp and nucellus) prevents miniendosperm growth and development. We assume the formation of lobes and trichomes is an adaptive response of in vitro maize endosperm to high temperatures.

Differences in hydrolytic enzyme activity accompany natural variation in mature aleurone morphology in barley (Hordeum vulgare L.)

The aleurone is a critical component of the cereal seed and is located at the periphery of the starchy endosperm. During germination, the aleurone is responsible for releasing hydrolytic enzymes that degrade cell wall polysaccharides and starch granules, which is a key requirement for barley malt production. Inter- and intra-species differences in aleurone layer number have been identified in the cereals but the significance of this variation during seed development and germination remains unclear. In this study, natural variation in mature aleurone features was examined in a panel of 33 Hordeum vulgare (barley) genotypes. Differences were identified in the number of aleurone cell layers, the transverse thickness of the aleurone and the proportion of aleurone relative to starchy endosperm. In addition, variation was identified in the activity of hydrolytic enzymes that are associated with germination. Notably, activity of the free fraction of β-amylase (BMY), but not the bound fraction, was increased at grain maturity in barley varieties possessing more aleurone. Laser capture microdissection (LCM) and transcriptional profiling confirmed that HvBMY1 is the most abundant BMY gene in developing grain and accumulates in the aleurone during early stages of grain fill. The results reveal a link between molecular pathways influencing early aleurone development and increased levels of free β-amylase enzyme, potentially highlighting the aleurone as a repository of free β-amylase at grain maturity.

Instability of endosperm development in amphiploids and their parental species in the genus Avena L.

Key messageThe development of oat endosperm is modified by chromatin and nuclei elimination, intrusive growth of cell walls, and polyploidisation of cell clones. The last event is correlated with somatic crossing-over.Grass endosperm is a variable tissue in terms of its cytogenetics and development. Free-nuclear syncytium and starchy and aleurone endosperm were the main focus of the research. These were studied in oat amphiploids (4x, 6x, and 8x) and parental species (2x, 4x, and 6x). What the levels of cytogenetic disorders and developmental anomalies in species versus hybrids are, and, what the factors are determining phenotypes of both tissue components, are open questions for oats. Chromosome bridges and micronuclei are the main cytogenetic disorders showing the elimination of parts of genomes. Bridges are formed by the AT-heterochromatin-rich and -free ends of chromosomes. In the starchy tissue, various sectors are separated structurally due to the elongation or intrusive growth of aleurone cells. The development of the aleurone layer is highly disturbed locally due to the amplification of aleurone cell divisions. Changes related to their structure and metabolism occur in the aleurone cells, for example, clones of small versus large aleurone cells. Somatic crossing-over (SCO) is expressed in clones of large polyploidised cells (r = 0.80***), giving rise to new aleurone phenotypes. The multivariate description of the endosperm instability showed that endospermal disorders were more frequent in amphiploids than in the oat species. Avena strigosa and the amphiploid A. fatua × A. sterilis appeared to be extreme units in an ordination space. Nuclear DNA elimination, periclinal and multidirectional cytokineses, polyploidisation, intrusive growth, and SCO appeared to be important factors determining oat endospermal variations.