Sister chromatid separation and monopolar spindle organization in the first meiosis as two mechanisms of unreduced gametes formation in wheat–rye hybrids

Abstract

Key messageUnreduced gametes.AbstractThe absence of a strict pachytene checkpoint in plants presents an opportunity to study meiosis in polyhaploid organisms. In the present study, we demonstrate that meiosis is coordinated in hybrids between disomic wheat–rye substitution lines 1Rv(1A), 2R(2D), 5R(5D), 6R(6A) and rye (Triticum aestivum L. × Secale cereale L., 4x = 28, ABDR). By using in situ hybridization with a centromere pAet6-09 probe and immunostaining with H3Ser10ph-, CENH3-, and α-tubulin-specific antibodies, we distinguished four chromosome behaviour types. The first one is a mitotic-like division that is characterized by mitotic centromere architecture, robust bipolar spindle, one-step loss of arm and centromere cohesion, and sister chromatid separation in the first and only meiotic division. The second type involves a monopolar spindle formation, which appears as a hat-shaped group of chromosomes moving in one direction, wherein MT bundles are co-oriented polewards. It prevents chromosome segregation in meiosis I, with a bipolar spindle distributing sister chromatids to the poles in meiosis II. These events subsequently result in the formation of unreduced microspores. The other two meiotic-like chromosome segregation patterns known as reductional and equational plus reductional represent stand-alone types of cell division rather than intermediate steps of meiosis I. Only sterile pollen is produced as a result of such meiotic-like chromosome behaviours. Slightly variable meiotic phenotypes are reproducibly observed in hybrids under different growth conditions. The 2R(2D)xR genotype tends to promote reductional division. In contrast, the genotypes 1Rv(1A)xR, 5R(5D)xR, and 6R(6A)xR promote equational chromosome segregation and monopolar spindle formation in addition to reductional and equational plus reductional division types.Electronic supplementary materialThe online version of this article (doi:10.1007/s00497-016-0279-5) contains supplementary material, which is available to authorized users.

In Silico Characterization of a Cyclin Dependent Kinase -A (CDKA) and its Coding Gene in some Oryza Species

“…In nucleus, CDKA is involved in DNA replication (36) and formation of synaptonemal complex at the beginning of meiosis (18). In cytoplasm, CDKA is associated with spindle (37,38) and phragmoplast formation (39 Analyses of the amino acid sequences of CDKA mined from the studied Oryza genomes showed 291-292 amino acid length in all species except O. longistaminata that appeared as a shorter amino acid chain of 273 residues (Fig. 3).…”

Random chromosome distribution in the first meiosis of F1 disomic substitution line 2R(2D) x rye hybrids (ABDR, 4× = 28) occurs without bipolar spindle assembly

“…Fluorescence in situ hybridisation ( FISH ) was performed according to Silkova and Loginova (2016) . Spikes were fixed in 45% acetic acid for 2 to 4 h at room temperature, anthers with meiocytes at MI-AI were selected, squashed and slides were frozen in liquid nitrogen, dehydrated through a series of alcohols with increasing concentrations of 70%, 90% and 96% and stored at –20 °C until needed.…”

“…First-generation hybrids between species/genera of different taxa constitute a complex organism; its nucleus unites several haploid genomes. Previously, our group described four types of meiotic chromosome behaviour in hybrids (2n = 4× = 28, ABDR ) between the disomic wheat-rye substitution lines 1Rv(1A), 2R(2D), 5R(5D), 6R(6A) and rye ( Silkova and Loginova 2016 ). Two of them are significantly different from each other.…”

“…Thus, a bipolar spindle is formed in meiosis of wheat-rye hybrids when bipolar-directed kinetochores are present ( Silkova and Loginova 2016 ), similar to asynaptic mutants and haploids ( Chan and Cande 1998 , Xue et al 2019 ). Little is known, so far, as to how the spindle is formed and chromosomes are distributed to daughter cells in meiosis with monopolar-directed kinetochores.…”

Peculiarities of Kariotype Stabilization in the Progeny From Crossing of the Wheat-Rye Substituted Line 1r(1a) With Diploid Rye

“…Результаты и их обсуждение. Характерной особенностью использованных в данной работе генотипов пшеницы и ржи является способность детерминировать в мейозе полученных на их основе амфигаплоидов ABDR деление, подобное митозу, что способствует образованию нередуцированных гамет и, как следствие, обеспечивает частичную фертильность гибридного материала [15]. При этом механизмы образования нередуцированных гамет могут быть разными, что было установлено в ходе изучения поведения хромосом в мейозе амфигаплоидов, в геномах которых различные хромосомы пшеницы были замещены соответствующими гомеологами ржи [16].…”