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

Abstract

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.AbstractGrass 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.

Complex polyploid and hybrid species in an apomictic and sexual tropical forage grass group: genomic composition and evolution inUrochloa(Brachiaria) species

“…The integration of sequencing, molecular cytogenetic and bioinformatic tools allows the identification of genomes which come together in polyploids (Soltis et al ., 2013). Many crop species with polyploid members, including Brassica (Alix et al ., 2008) and the Brassicaceae (Cheng et al ., 2013), Avena (Tomaszewska and Kosina, 2018; Liu et al ., 2019) and particularly the tribe Triticeae (Hordeae) (Linde-Laursen et al ., 1997) have well-established genome designations (as single letters) to describe the ancestral genomes in auto- and allo-polyploids (amphiploids). Resolution of genome relationships in the wheat group has assisted with extensive use of the germplasm pool in breeding (Feldman and Sears, 1981; Ali et al ., 2016; Rasheed et al ., 2018).…”

Cytogenetic events in the endosperm of amphiploidAvena maroccana×A. longiglumis

“…These cytogenetic events can be more frequently observed in the endosperm than in root meristems; however, the selection of dysfunctional nuclei decreases the number of chromosomes and their rearrangements that could be observed in the endosperm (Table 1; Tomaszewska 2017). This type of selection is commonly made through the apoptosis process (Tomaszewska and Kosina 2018).…”

Endosperm variability: from endoreduplication within a seed to higher ploidy across species, and its competence

“…The variability in ploidy level of endosperm across species or hybrids derived between parents at different ploidy levels is prominent in crossable species wherein fertile seeds are produced, involving parents differing in their ploidy (Tomaszewska and Kosina, 2018). Remarkably, the variability of endosperm ploidy within a seed was reported well before the DNA-double helix structure (Duncan and Ross, 1950; Swift, 1950).…”

“…Defective kernel ( Dek ) mutants in maize exhibit reduced mitotic activity and, in turn, the endoreduplication, especially in the central regions of endosperm cell, was found to be controlled by a recessive gene (Kowles et al, 1992a) and also lacking an aleurone layer (Becraft and Yi, 2010). Water deficit (Artlip et al, 1995), abscisic acid (Mambelli and Setter, 1998), high temperature (Engelen-Eigles et al, 2000), parental dosage effect (Kowles et al, 1997; Leblanc et al, 2002; Tomaszewska and Kosina, 2018) and post-translational modification (Zhao and Grafi, 2000) may alter endoreduplication through regulating mitotic cycles in the endosperm, thereby suggesting multiple checkpoints, besides some recessive genes. Key molecular mechanisms involved in endoreduplication and increased ploidy level within the seed were identified as primarily due to the loss of activity of M-phase cyclin-dependent kinase and alterations in S-phase cyclin-dependent kinase (Larkins et al, 2001).…”

“…It has been estimated that roughly 3% of the total endosperm cells (positioned in the central region) in maize seed exhibit the variability in ploidy from the normal triploid endosperm cells, and a few cells (approximately 1%) contained around 90 chromosomes (Lin, 1977). Ploidy variability, like in maize, has been reported in oats, as well (Tomaszewska and Kosina, 2018). Later, endoreduplication in plants was found in cotyledons, roots, cell suspensions, anthers, developing fruits (tomato) and leaves, as well (Joubès and Chevalier, 2000).…”