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

Paulina Tomaszewska,Romuald Kosina

doi:10.1007/s00299-018-2301-x

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.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.

Highlights

Some genetic and developmental phenomena are characteristics for endosperm tissue
For cytogenetic analyses of the freenuclear syncytium, as well as endosperm tissue from ripe caryopses of six oat amphiploids and their parental species were sampled from plants, that were cultivated on small plots or in pots in the grass collection (Wroclaw, SW Poland), maintained by R
Various cytogenetic disorders were noted for both types of oats: amphiploids and parental species

Summary

Introduction

Some genetic and developmental phenomena are characteristics for endosperm tissue. Polyploidy and chromosomal disorders have been recognised to be common in the developing endosperm (Vijayaraghavan and Prabhakar 1984). McClintock’s important classical study on Zea mays provided strong data on the cytogenetics and development of endosperm (McClintock 1987). She evidenced transposons’ activity in the endosperm tissue and its clonal nature. Within a clone, developed from the outside towards the caryopsis inside, internal cells are large and polyploidised, while the external cells are younger and still undergoing division Such a development indicates the direction of the endoreduplication gradient (Becraft and Gutierres-Marcos 2012). The endoreduplication and the metabolite storage potential decrease towards the outer parts of the caryopsis, and probably, both these processes are closely related Such a clonal nature determines tissue patterns expressed during the endosperm development. A further in-depth study using molecular methods provided new data

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