Cytomixis doesn’t induce obvious changes in chromatin modifications and programmed cell death in tobacco male meiocytes

Abstract

Cytomixis is a poorly studied process of nuclear migration between plant cells. It is so far unknown what drives cytomixis and what is the functional state of the chromatin migrating between cells. Using immunostaining, we have analyzed the distribution of posttranslational histone modifications (methylation, acetylation, and phosphorylation) that reflect the functional state of chromatin in the tobacco microsporocytes involved in cytomixis. We demonstrate that the chromatin in the cytomictic cells does not differ from the chromatin in intact microsporocytes according to all 14 analyzed histone modification types. We have also for the first time demonstrated that the migrating chromatin contains normal structures of the synaptonemal complex (SC) and lacks any signs of apoptosis. As has been shown, the chromatin migrating between cells in cytomixis is neither selectively heterochromatized nor degraded both before its migration to another cell and after it enters a recipient cell as micronuclei. We also showed that cytomictic chromatin contains marks typical for transcriptionally active chromatin as well as heterochromatin. Moreover, marks typical for chromosome condensation, SC formation and key proteins required for the formation of bivalents were also detected at migrated chromatin.

Tackling Plant Meiosis: From Model Research to Crop Improvement

“…Due to slow-paced progression during prophase I, for instance, assembly/disassembly of the bouquet and the SC or formation and dissolution of interlocks could be studied in detail. In numerous plant species, primarily during male prophase I, cytomixis occurs, i.e., migration of whole nuclei, chromosomes and/or chromatin between plant cells through intercellular channels (cytomictic channels) resulting in the formation of unreduced, polyploid, aneuploid or sterile pollen ( Mursalimov et al, 2015 ; Mursalimov and Deineko, 2017 ). How cytomixis is regulated or interconnected to meiotic progression is unclear.…”

Cytoskeleton and nucleoskeleton involvement in processes of cytomixis in plants

“…Some scientists suggest that the chromosomal polymorphisms of microsporocytes and pollen grains, as well as a large variety of natural polyploid cytotypes in many plant species confirm the involvement of migrant chromatin in the karyotype restructuring (Zheng et al, 1987;Zhou, 2003;Malallah and Attia, 2003;Lattoo et al, 2006;Ghaffari, 2006;Lattoo et al. 2006;Negron-Ortiz, 2007;Kumar and Singhal, 2008;Pierre e de and Sousa, 2011;Singhal et al, 2011a,b;Rana et al, 2013;Mandal et al, 2013;Mursalimov et al, 2013Mursalimov et al, , 2015bReis et al, 2015).…”

“…Using electron and fluorescence microscopy, transgenic plants expressing H2B‐CFP as well as FISH‐method for marking telomeric repeats of chromosomes, it was shown that the nuclear envelope and chromatin remain intact in cytomictic migrations (Wang et al, ; Liu et al, ; Mursalimov and Deineko, ; Mursalimov et al, ,). In these experiments the micronuclei and migrating chromatin emitted multiple telomeric signals, which were either localized in clusters or dispersed, depending upon the meiosis stage (Mursalimov et al, ).…”

Cytomixis as a primary form of sexual process

“…8,[13][14][15][16] On transgenic tobacco lines showed that cytomictic chromatin retains not only its physical, but functional properties as well. [17][18][19] The chromosomal polymorphism of microsporocytes and pollen grains, the existence of a large variety of natural polyploid cytotypes in many cytomictic species as well as fact that cytomixis is attributed to male generative sphere and "male-driven" evolution allow us to consider cytomixis as one of the mechanisms to increase genetic diversity and speciation in plants. 2,[8][9][10][11][12][16][17][18][20][21][22] The wide occurrence of cytomixis in terrestrial plants testifies its being involved in the important genomic reorganization processes, which allow its carriers to be maintained due to natural selection process.…”